refactor: monogame camera transform caching

Original Behaviour was using old methods for detecting entering/exiting universe,
they are now all under the same hood and the original is kept for UniverseEntranceManager
because it needs to enter the universe without itself. The internal behaviour kept under
a subnamespace of "Core.Internal" for the purpose that it might come in handy for other use cases.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "Engine.Integration/YamlDotNet"]
+	path = Engine.Integration/YamlDotNet
+	url = https://github.com/Syntriax/YamlDotNet.git

Engine.Core/.gitignore

@@ -482,3 +482,5 @@ $RECYCLE.BIN/
 
 # Vim temporary swap files
 *.swp
+
+!Debug

Engine.Core/Abstract/Assignable/IAssignable.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Indicates the class implementing it has Assignable fields that are necessary for the engine to work properly.
@@ -8,7 +8,7 @@ public interface IAssignable
     /// <summary>
     /// Event triggered when the <see cref="IAssignable"/>'s fields are unassigned and completely ready to recycle.
     /// </summary> 
-    event UnassignEventHandler? OnUnassigned;
+    Event<IAssignable>? OnUnassigned { get; }
 
     /// <summary>
     /// Unassign <see cref="IAssignable"/>'s all fields and make it ready to recycle.
@@ -17,6 +17,4 @@ public interface IAssignable
     /// <see cref="true"/>, if the fields are unsigned successfully, <see cref="false"/> if not.
     /// </returns>
     bool Unassign();
-
-    delegate void UnassignEventHandler(IAssignable sender);
 }

Engine.Core/Abstract/Assignable/IHasBehaviourController.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IBehaviourController"/> field.
@@ -8,7 +8,7 @@ public interface IHasBehaviourController : IAssignable
     /// <summary>
     /// Event triggered when the <see cref="IBehaviourController"/> value has has been assigned a new value.
     /// </summary>
-    event BehaviourControllerAssignedEventHandler? OnBehaviourControllerAssigned;
+    Event<IHasBehaviourController> OnBehaviourControllerAssigned { get; }
 
     /// <inheritdoc cref="IBehaviourController" />
     IBehaviourController BehaviourController { get; }
@@ -21,6 +21,4 @@ public interface IHasBehaviourController : IAssignable
     /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
     /// </returns>
     bool Assign(IBehaviourController behaviourController);
-
-    delegate void BehaviourControllerAssignedEventHandler(IHasBehaviourController sender);
 }

Engine.Core/Abstract/Assignable/IHasEntity.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IEntity"/> field.
@@ -8,7 +8,7 @@ public interface IHasEntity : IAssignable
     /// <summary>
     /// Event triggered when the <see cref="IEntity"/> value has has been assigned a new value.
     /// </summary>
-    event EntityAssignedEventHandler? OnEntityAssigned;
+    Event<IHasEntity> OnEntityAssigned { get; }
 
     /// <inheritdoc cref="IEntity" />
     IEntity Entity { get; }
@@ -21,6 +21,4 @@ public interface IHasEntity : IAssignable
     /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
     /// </returns>
     bool Assign(IEntity entity);
-
-    delegate void EntityAssignedEventHandler(IHasEntity sender);
 }

Engine.Core/Abstract/Assignable/IHasGameManager.cs

@@ -1,26 +0,0 @@
-namespace Syntriax.Engine.Core.Abstract;
-
-/// <summary>
-/// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="ITransform2D"/> field.
-/// </summary>
-public interface IHasGameManager : IAssignable
-{
-    /// <summary>
-    /// Event triggered when the <see cref="IGameManager"/> value has has been assigned a new value.
-    /// </summary>
-    event GameManagerAssignedEventHandler? OnGameManagerAssigned;
-
-    /// <inheritdoc cref="IGameManager" />
-    IGameManager GameManager { get; }
-
-    /// <summary>
-    /// Assign a value to the <see cref="IGameManager"/> field of this object.
-    /// </summary>
-    /// <param name="gameManager">New <see cref="IGameManager"/> to assign.</param>
-    /// <returns> 
-    /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
-    /// </returns>
-    bool Assign(IGameManager gameManager);
-
-    delegate void GameManagerAssignedEventHandler(IHasGameManager sender);
-}

Engine.Core/Abstract/Assignable/IHasHierarchyObject.cs

@@ -1,26 +0,0 @@
-namespace Syntriax.Engine.Core.Abstract;
-
-/// <summary>
-/// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IHierarchyObject"/> field.
-/// </summary>
-public interface IHasHierarchyObject : IAssignable
-{
-    /// <summary>
-    /// Event triggered when the <see cref="IHierarchyObject"/> value has has been assigned a new value.
-    /// </summary>
-    event HierarchyObjectAssignedEventHandler? OnHierarchyObjectAssigned;
-
-    /// <inheritdoc cref="IHierarchyObject" />
-    IHierarchyObject HierarchyObject { get; }
-
-    /// <summary>
-    /// Assign a value to the <see cref="IHierarchyObject"/> field of this object.
-    /// </summary>
-    /// <param name="hierarchyObject">New <see cref="IHierarchyObject"/> to assign.</param>
-    /// <returns> 
-    /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
-    /// </returns>
-    bool Assign(IHierarchyObject hierarchyObject);
-
-    delegate void HierarchyObjectAssignedEventHandler(IHasHierarchyObject sender);
-}

Engine.Core/Abstract/Assignable/IHasStateEnable.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IStateEnable"/> field.
@@ -8,7 +8,7 @@ public interface IHasStateEnable : IAssignable
     /// <summary>
     /// Event triggered when the <see cref="IStateEnable"/> value has has been assigned a new value.
     /// </summary>
-    event StateEnableAssignedEventHandler? OnStateEnableAssigned;
+    Event<IHasStateEnable> OnStateEnableAssigned { get; }
 
     /// <inheritdoc cref="IStateEnable" />
     IStateEnable StateEnable { get; }
@@ -21,6 +21,4 @@ public interface IHasStateEnable : IAssignable
     /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
     /// </returns>
     bool Assign(IStateEnable stateEnable);
-
-    delegate void StateEnableAssignedEventHandler(IHasStateEnable sender);
 }

Engine.Core/Abstract/Assignable/IHasUniverse.cs

@@ -0,0 +1,24 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IUniverse"/> field.
+/// </summary>
+public interface IHasUniverse : IAssignable
+{
+    /// <summary>
+    /// Event triggered when the <see cref="IUniverse"/> value has has been assigned a new value.
+    /// </summary>
+    Event<IHasUniverse> OnUniverseAssigned { get; }
+
+    /// <inheritdoc cref="IUniverse" />
+    IUniverse Universe { get; }
+
+    /// <summary>
+    /// Assign a value to the <see cref="IUniverse"/> field of this object.
+    /// </summary>
+    /// <param name="universe">New <see cref="IUniverse"/> to assign.</param>
+    /// <returns> 
+    /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
+    /// </returns>
+    bool Assign(IUniverse universe);
+}

Engine.Core/Abstract/Assignable/IHasUniverseObject.cs

@@ -0,0 +1,24 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IUniverseObject"/> field.
+/// </summary>
+public interface IHasUniverseObject : IAssignable
+{
+    /// <summary>
+    /// Event triggered when the <see cref="IUniverseObject"/> value has has been assigned a new value.
+    /// </summary>
+    Event<IHasUniverseObject> OnUniverseObjectAssigned { get; }
+
+    /// <inheritdoc cref="IUniverseObject" />
+    IUniverseObject UniverseObject { get; }
+
+    /// <summary>
+    /// Assign a value to the <see cref="IUniverseObject"/> field of this object.
+    /// </summary>
+    /// <param name="universeObject">New <see cref="IUniverseObject"/> to assign.</param>
+    /// <returns> 
+    /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
+    /// </returns>
+    bool Assign(IUniverseObject universeObject);
+}

Engine.Core/Abstract/IActive.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents an entity which can be active or not.
@@ -8,12 +8,12 @@ public interface IActive
     /// <summary>
     /// Event triggered when the <see cref="IsActive"/> state of the <see cref="IActive"/> changes.
     /// </summary>
-    event ActiveChangedEventHandler? OnActiveChanged;
+    Event<IActive, ActiveChangedArguments> OnActiveChanged { get; }
 
     /// <summary>
     /// The value indicating whether the <see cref="IActive"/> is enabled.
     /// </summary>
     bool IsActive { get; }
 
-    delegate void ActiveChangedEventHandler(IActive sender, bool previousState);
+    readonly record struct ActiveChangedArguments(bool PreviousState);
 }

Engine.Core/Abstract/IBehaviour.cs

@@ -1,19 +1,19 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
-/// Represents a behaviour that any object in the game might use to interact with itself or other objects. 
+/// Represents a behaviour that any object in the engine that might use to interact with itself or other objects. 
 /// </summary>
 public interface IBehaviour : IEntity, IActive, IHasBehaviourController, IHasStateEnable
 {
     /// <summary>
     /// Event triggered when the priority of the <see cref="IBehaviour"/> changes.
     /// </summary>
-    event PriorityChangedEventHandler? OnPriorityChanged;
+    Event<IBehaviour, PriorityChangedArguments> OnPriorityChanged { get; }
 
     /// <summary>
     /// The priority of the <see cref="IBehaviour"/>.
     /// </summary>
     int Priority { get; set; }
 
-    delegate void PriorityChangedEventHandler(IBehaviour sender, int previousPriority);
+    readonly record struct PriorityChangedArguments(int PreviousPriority);
 }

Engine.Core/Abstract/IBehaviour2D.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 public interface IBehaviour2D : IBehaviour
 {

Engine.Core/Abstract/IBehaviour3D.cs

@@ -0,0 +1,6 @@
+namespace Engine.Core;
+
+public interface IBehaviour3D : IBehaviour
+{
+    ITransform3D Transform { get; }
+}

Engine.Core/Abstract/IBehaviourCollector.cs

@@ -1,35 +1,42 @@
-using System.Collections.Generic;
+namespace Engine.Core;
-
-namespace Syntriax.Engine.Core.Abstract;
 
 /// <summary>
 /// Represents a collector for the class type of <typeparamref name="T"/>.
-/// Provides mechanisms for tracking additions and removals, and notifies subscribers when such events occur on the assigned <see cref="IGameManager"/>.
+/// Provides mechanisms for tracking additions and removals, and notifies subscribers when such events occur on the assigned <see cref="IUniverse"/>.
 /// </summary>
 /// <typeparam name="T">The type of objects tracked by the collector.</typeparam>
-public interface IBehaviourCollector<T> : IHasGameManager, IEnumerable<T> where T : class
+public interface IBehaviourCollector<T> : IHasUniverse where T : class
 {
     /// <summary>
     /// Event triggered when an object of type <typeparamref name="T"/> is added to the collector.
     /// </summary>
-    event CollectedEventHandler? OnCollected;
+    Event<IBehaviourCollector<T>, BehaviourCollectedArguments> OnCollected { get; }
 
     /// <summary>
     /// Event triggered when an object of type <typeparamref name="T"/> is removed from the collector.
     /// </summary>
-    event RemovedEventHandler? OnRemoved;
+    Event<IBehaviourCollector<T>, BehaviourRemovedArguments> OnRemoved { get; }
+
+    /// <summary>
+    /// Amount of <typeparamref name="T"/> collected.
+    /// </summary>
+    int Count { get; }
+
+    /// <summary>
+    /// Get a <typeparamref name="T"/> collected by it's index.
+    /// </summary>
+    T this[System.Index index] { get; }
 
     /// <summary>
     /// Delegate for handling the <see cref="OnCollected"/> event.
     /// </summary>
     /// <param name="sender">The instance of the <see cref="IBehaviourCollector{T}"/> that triggered the event.</param>
     /// <param name="behaviourCollected">The object of type <typeparamref name="T"/> that was added to the collector.</param>
-    delegate void CollectedEventHandler(IBehaviourCollector<T> sender, T behaviourCollected);
+    readonly record struct BehaviourCollectedArguments(T BehaviourCollected);
 
     /// <summary>
     /// Delegate for handling the <see cref="OnRemoved"/> event.
     /// </summary>
-    /// <param name="sender">The instance of the <see cref="IBehaviourCollector{T}"/> that triggered the event.</param>
+    /// <param name="BehaviourRemoved">The object of type <typeparamref name="T"/> that was removed from the collector.</param>
-    /// <param name="behaviourRemoved">The object of type <typeparamref name="T"/> that was removed from the collector.</param>
+    readonly record struct BehaviourRemovedArguments(T BehaviourRemoved);
-    delegate void RemovedEventHandler(IBehaviourCollector<T> sender, T behaviourRemoved);
 }

Engine.Core/Abstract/IBehaviourController.cs

@@ -1,36 +1,31 @@
 using System.Collections.Generic;
 
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
-/// Represents a controller for managing <see cref="IBehaviour"/>s and notify them accordingly about the engine's updates. Connected to an <see cref="IHierarchyObject"/>.
+/// Represents a controller for managing <see cref="IBehaviour"/>s. Connected to an <see cref="IUniverseObject"/>.
 /// </summary>
-public interface IBehaviourController : IInitializable, IHasHierarchyObject, IEnumerable<IBehaviour>
+public interface IBehaviourController : IEntity, IHasUniverseObject
 {
-    /// <summary>
-    /// Event triggered before the update of <see cref="IBehaviour"/>s.
-    /// </summary>
-    event PreUpdateEventHandler? OnPreUpdate;
-
-    /// <summary>
-    /// Event triggered during the update of <see cref="IBehaviour"/>s.
-    /// </summary>
-    event UpdateEventHandler? OnUpdate;
-
-    /// <summary>
-    /// Event triggered before the drawing phase.
-    /// </summary>
-    event PreDrawEventHandler? OnPreDraw;
-
     /// <summary>
     /// Event triggered when a <see cref="IBehaviour"/> is added to the <see cref="IBehaviourController"/>.
     /// </summary>
-    event BehaviourAddedEventHandler? OnBehaviourAdded;
+    Event<IBehaviourController, BehaviourAddedArguments> OnBehaviourAdded { get; }
 
     /// <summary>
     /// Event triggered when a <see cref="IBehaviour"/> is removed from the <see cref="IBehaviourController"/>.
     /// </summary>
-    event BehaviourRemovedEventHandler? OnBehaviourRemoved;
+    Event<IBehaviourController, BehaviourRemovedArguments> OnBehaviourRemoved { get; }
+
+    /// <summary>
+    /// Amount of <see cref="IBehaviour"/> collected.
+    /// </summary>
+    int Count { get; }
+
+    /// <summary>
+    /// Get a <see cref="IBehaviour"/> collected by it's index.
+    /// </summary>
+    IBehaviour this[System.Index index] { get; }
 
     /// <summary>
     /// Adds a <see cref="IBehaviour"/> to the <see cref="IBehaviourController"/>.
@@ -60,14 +55,15 @@ public interface IBehaviourController : IInitializable, IHasHierarchyObject, IEn
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
     /// <returns>A list of <see cref="IBehaviour"/>s of the specified type.</returns>
-    IList<T> GetBehaviours<T>();
+    IReadOnlyList<T> GetBehaviours<T>();
 
     /// <summary>
     /// Gets all <see cref="IBehaviour"/>s of the specified type and stores them in the provided list.
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
     /// <param name="results">The list to store the <see cref="IBehaviour"/>s.</param>
-    void GetBehaviours<T>(IList<T> results);
+    /// <param name="collectionMethod">Whether to clear the <paramref name="results"/> before collection or append the results to the list.</param>
+    void GetBehaviours<T>(IList<T> results, CollectionMethod collectionMethod = CollectionMethod.Clear);
 
     /// <summary>
     /// Removes <see cref="IBehaviour"/>s of the specified type from the <see cref="IBehaviourController"/>.
@@ -83,20 +79,8 @@ public interface IBehaviourController : IInitializable, IHasHierarchyObject, IEn
     /// <param name="behaviour">The <see cref="IBehaviour"/> to remove.</param>
     void RemoveBehaviour<T>(T behaviour) where T : class, IBehaviour;
 
-    /// <summary>
+    enum CollectionMethod { Clear, Append };
-    /// Updates all <see cref="IBehaviour"/>s in the <see cref="IBehaviourController"/>.
-    /// </summary>
-    void Update();
-
-    /// <summary>
-    /// Performs pre-draw operations.
-    /// </summary>
-    void UpdatePreDraw();
-
-    delegate void PreUpdateEventHandler(IBehaviourController sender);
-    delegate void UpdateEventHandler(IBehaviourController sender);
-    delegate void PreDrawEventHandler(IBehaviourController sender);
-    delegate void BehaviourAddedEventHandler(IBehaviourController sender, IBehaviour behaviourAdded);
-    delegate void BehaviourRemovedEventHandler(IBehaviourController sender, IBehaviour behaviourRemoved);
 
+    readonly record struct BehaviourAddedArguments(IBehaviour BehaviourAdded);
+    readonly record struct BehaviourRemovedArguments(IBehaviour BehaviourRemoved);
 }

Engine.Core/Abstract/ICamera2D.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents a 2D camera in the engine.

Engine.Core/Abstract/ICamera3D.cs

@@ -0,0 +1,55 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Represents a 3D camera in the engine.
+/// </summary>
+public interface ICamera3D : IBehaviour3D
+{
+    /// <summary>
+    /// Event triggered when the near plane of the <see cref="ICamera3D"/> changes.
+    /// </summary>
+    Event<ICamera3D, NearPlaneChangedArguments> OnNearPlaneChanged { get; }
+
+    /// <summary>
+    /// Event triggered when the far plane of the <see cref="ICamera3D"/> changes.
+    /// </summary>
+    Event<ICamera3D, FarPlaneChangedArguments> OnFarPlaneChanged { get; }
+
+    /// <summary>
+    /// Event triggered when the field of view of the <see cref="ICamera3D"/> changes.
+    /// </summary>
+    Event<ICamera3D, FieldOfViewChangedArguments> OnFieldOfViewChanged { get; }
+
+    /// <summary>
+    /// Near plane distance of the camera.
+    /// </summary>
+    float NearPlane { get; set; }
+
+    /// <summary>
+    /// Far plane distance of the camera.
+    /// </summary>
+    float FarPlane { get; set; }
+
+    /// <summary>
+    /// Field of View (FOV) value of the camera in degrees.
+    /// </summary>
+    float FieldOfView { get; set; }
+
+    /// <summary>
+    /// Converts a position from screen coordinates to a <see cref="Ray3D"/>.
+    /// </summary>
+    /// <param name="screenPosition">The position in screen coordinates.</param>
+    /// <returns>The <see cref="Ray3D"/> originating from the camera to the screen position in world coordinates.</returns>
+    Ray3D ScreenToWorldRay(Vector2D screenPosition);
+
+    /// <summary>
+    /// Converts a position from world coordinates to screen coordinates.
+    /// </summary>
+    /// <param name="worldPosition">The position in world coordinates.</param>
+    /// <returns>The position in screen coordinates.</returns>
+    Vector2D WorldToScreenPosition(Vector3D worldPosition);
+
+    readonly record struct NearPlaneChangedArguments(float PreviousNearPlane);
+    readonly record struct FarPlaneChangedArguments(float PreviousFarPlane);
+    readonly record struct FieldOfViewChangedArguments(float PreviousFieldOfView);
+}

Engine.Core/Abstract/ICoroutineYield.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 public interface ICoroutineYield
 {

Engine.Core/Abstract/IEntity.cs

@@ -1,20 +1,6 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents a basic entity in the engine.
 /// </summary>
-public interface IEntity : IInitializable, IHasStateEnable
+public interface IEntity : IInitializable, IIdentifiable, IHasStateEnable;
-{
-    /// <summary>
-    /// Event triggered when the <see cref="Id"/> of the <see cref="IEntity"/> changes.
-    /// The string action parameter is the previous <see cref="Id"/> of the <see cref="IEntity"/>. 
-    /// </summary>
-    event IdChangedEventHandler? OnIdChanged;
-
-    /// <summary>
-    /// The ID of the <see cref="IEntity"/>.
-    /// </summary>
-    string Id { get; set; }
-
-    delegate void IdChangedEventHandler(IEntity sender, string previousId);
-}

Engine.Core/Abstract/IGameManager.cs

@@ -1,81 +0,0 @@
-using System.Collections.Generic;
-
-namespace Syntriax.Engine.Core.Abstract;
-
-/// <summary>
-/// Represents a game world responsible for managing <see cref="IHierarchyObject"/>s.
-/// </summary>
-public interface IGameManager : IEntity, IEnumerable<IHierarchyObject>
-{
-    /// <summary>
-    /// Event triggered when <see cref="Update(EngineTime)"/> is about to be called called on the <see cref="IGameManager"/>.
-    /// </summary>
-    event UpdateEventHandler? OnPreUpdate;
-
-    /// <summary>
-    /// Event triggered when <see cref="Update(EngineTime)"/> is called on the <see cref="IGameManager"/>.
-    /// </summary>
-    event UpdateEventHandler? OnUpdate;
-
-    /// <summary>
-    /// Event triggered when <see cref="PreDraw"/> is called on the <see cref="IGameManager"/>.
-    /// </summary>
-    event PreDrawEventHandler? OnPreDraw;
-
-    /// <summary>
-    /// Event triggered when a <see cref="IHierarchyObject"/> is registered to the <see cref="IGameManager"/>.
-    /// </summary>
-    event HierarchyObjectRegisteredEventHandler? OnHierarchyObjectRegistered;
-
-    /// <summary>
-    /// Event triggered when a <see cref="IHierarchyObject"/> is unregistered from the <see cref="IGameManager"/>.
-    /// </summary>
-    event HierarchyObjectUnRegisteredEventHandler? OnHierarchyObjectUnRegistered;
-
-    /// <summary>
-    /// Contains time data related to this <see cref="IGameManager"/>.
-    /// </summary>
-    EngineTime Time { get; }
-
-    /// <summary>
-    /// Gets a read-only list of <see cref="IHierarchyObject"/>s managed by the <see cref="IGameManager"/>.
-    /// </summary>
-    IReadOnlyList<IHierarchyObject> HierarchyObjects { get; }
-
-    /// <summary>
-    /// Registers an <see cref="IHierarchyObject"/> to the <see cref="IGameManager"/>.
-    /// </summary>
-    /// <param name="hierarchyObject">The <see cref="IHierarchyObject"/> to register.</param>
-    void Register(IHierarchyObject hierarchyObject);
-
-    /// <summary>
-    /// Instantiates a <see cref="IHierarchyObject"/> of type T with the given arguments and registers it to the <see cref="IGameManager"/>.
-    /// </summary>
-    /// <typeparam name="T">The type of <see cref="IHierarchyObject"/> to instantiate.</typeparam>
-    /// <param name="args">Constructor parameters for the given type of <see cref="IHierarchyObject"/>.</param>
-    /// <returns>The instantiated <see cref="IHierarchyObject"/>.</returns>
-    T InstantiateHierarchyObject<T>(params object?[]? args) where T : class, IHierarchyObject;
-
-    /// <summary>
-    /// Removes an <see cref="IHierarchyObject"/> from the <see cref="IGameManager"/>.
-    /// </summary>
-    /// <param name="hierarchyObject">The <see cref="IHierarchyObject"/> to remove.</param>
-    void Remove(IHierarchyObject hierarchyObject);
-
-    /// <summary>
-    /// Updates the <see cref="IGameManager"/> with the given delta time.
-    /// </summary>
-    /// <param name="engineTime">Delta time.</param>
-    void Update(EngineTime engineTime);
-
-    /// <summary>
-    /// Performs operations that should be done before the draw calls.
-    /// </summary>
-    void PreDraw();
-
-    delegate void UpdateEventHandler(IGameManager sender, EngineTime engineTime);
-    delegate void PreDrawEventHandler(IGameManager sender);
-
-    delegate void HierarchyObjectRegisteredEventHandler(IGameManager sender, IHierarchyObject hierarchyObjectRegistered);
-    delegate void HierarchyObjectUnRegisteredEventHandler(IGameManager sender, IHierarchyObject hierarchyObjectUnregistered);
-}

Engine.Core/Abstract/IHasId.cs

@@ -0,0 +1,20 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Represents any instance in the engine with an id.
+/// </summary>
+public interface IIdentifiable
+{
+    /// <summary>
+    /// Event triggered when the <see cref="Id"/> of the <see cref="IIdentifiable"/> changes.
+    /// The string action parameter is the previous <see cref="Id"/> of the <see cref="IIdentifiable"/>. 
+    /// </summary>
+    Event<IIdentifiable, IdChangedArguments> OnIdChanged { get; }
+
+    /// <summary>
+    /// The ID of the <see cref="IIdentifiable"/>.
+    /// </summary>
+    string Id { get; set; }
+
+    readonly record struct IdChangedArguments(string PreviousId);
+}

Engine.Core/Abstract/IHierarchyObject.cs

@@ -1,131 +0,0 @@
-using System.Collections.Generic;
-
-namespace Syntriax.Engine.Core.Abstract;
-
-/// <summary>
-/// Represents an <see cref="IEntity"/> that can enter and exit a hierarchy within the <see cref="IGameManager"/> system.
-/// This interface allows for tracking the object's presence in the hierarchy and provides events 
-/// for notifying when the see enters or exits the hierarchy.
-/// </summary>
-public interface IHierarchyObject : IEntity, IActive, INameable, IHasBehaviourController, IEnumerable<IHierarchyObject>
-{
-    /// <summary>
-    /// Event triggered when the <see cref="IHierarchyObject"/> enters the hierarchy.
-    /// </summary>
-    event EnteredHierarchyEventHandler? OnEnteredHierarchy;
-
-    /// <summary>
-    /// Event triggered when the <see cref="IHierarchyObject"/> exits the hierarchy.
-    /// </summary>
-    event ExitedHierarchyEventHandler? OnExitedHierarchy;
-
-    /// <summary>
-    /// Event triggered when the <see cref="Parent"/> of the <see cref="IHierarchyObject"/> changes. The second parameter is the old <see cref="IHierarchyObject"/>.
-    /// </summary>
-    event ParentChangedEventHandler? OnParentChanged;
-
-    /// <summary>
-    /// Event triggered when a new <see cref="IHierarchyObject"/> is added to the <see cref="Children"/>.
-    /// </summary>
-    event ChildrenAddedEventHandler? OnChildrenAdded;
-
-    /// <summary>
-    /// Event triggered when an <see cref="IHierarchyObject"/> is removed from the <see cref="Children"/>.
-    /// </summary>
-    event ChildrenRemovedEventHandler? OnChildrenRemoved;
-
-    /// <summary>
-    /// Gets the <see cref="IGameManager"/> this <see cref="IHierarchyObject"/> is connected to, if any.
-    /// </summary>
-    IGameManager GameManager { get; }
-
-    /// <summary>
-    /// Indicates whether the <see cref="IHierarchyObject"/> is currently in the hierarchy.
-    /// </summary>
-    bool IsInHierarchy { get; }
-
-    /// <summary>
-    /// The parent <see cref="IHierarchyObject"/> of the <see cref="IHierarchyObject"/>.
-    /// </summary>
-    IHierarchyObject? Parent { get; }
-
-    /// <summary>
-    /// The <see cref="IHierarchyObject"/>s that have this <see cref="IHierarchyObject"/> as their <see cref="Parent"/>.
-    /// </summary>
-    IReadOnlyList<IHierarchyObject> Children { get; }
-
-    /// <summary>
-    /// Internal method to handle entering the hierarchy.
-    /// This should be called by the system to properly manage hierarchy states.
-    /// </summary>
-    /// <param name="gameManager">The <see cref="IGameManager"/> that is managing this hierarchy.</param>
-    /// <returns>
-    /// <see cref="true"/> if the <see cref="IHierarchyObject"/> successfully entered the hierarchy; 
-    /// <see cref="false"/> if it failed to do so.
-    /// </returns>
-    internal bool EnterHierarchy(IGameManager gameManager);
-
-    /// <summary>
-    /// Internal method to handle exiting the hierarchy.
-    /// This should be called by the system to properly manage hierarchy states.
-    /// </summary>
-    /// <returns>
-    /// <see cref="true"/> if the <see cref="IHierarchyObject"/> successfully exited the hierarchy; 
-    /// <see cref="false"/> if it failed to do so.
-    /// </returns>
-    internal bool ExitHierarchy();
-
-    /// <summary>
-    /// Sets the parent <see cref="IHierarchyObject"/> of this <see cref="IHierarchyObject"/>.
-    /// </summary>
-    /// <param name="hierarchyObject">The parent <see cref="IHierarchyObject"/> to set.</param>
-    void SetParent(IHierarchyObject? hierarchyObject);
-
-    /// <summary>
-    /// Adds a child <see cref="IHierarchyObject"/> to this <see cref="IHierarchyObject"/>.
-    /// </summary>
-    /// <param name="hierarchyObject">The child <see cref="IHierarchyObject"/> to add.</param>
-    void AddChild(IHierarchyObject hierarchyObject);
-
-    /// <summary>
-    /// Removes a child <see cref="IHierarchyObject"/> from this <see cref="IHierarchyObject"/>.
-    /// </summary>
-    /// <param name="hierarchyObject">The child <see cref="IHierarchyObject"/> to remove.</param>
-    void RemoveChild(IHierarchyObject hierarchyObject);
-
-    /// <summary>
-    /// EventHandler delegate for the event triggered when the <see cref="IHierarchyObject"/> enters the hierarchy of a <see cref="IGameManager">.
-    /// </summary>
-    /// <param name="sender">The <see cref="IHierarchyObject"/> that entered the hierarchy.</param>
-    /// <param name="gameManager">The <see cref="IGameManager"/> that the <see cref="IHierarchyObject"/> has entered it's hierarchy.</param>
-    delegate void EnteredHierarchyEventHandler(IHierarchyObject sender, IGameManager gameManager);
-
-    /// <summary>
-    /// EventHandler delegate for the event triggered when the <see cref="IHierarchyObject"/> exits the hierarchy of a <see cref="IGameManager">.
-    /// </summary>
-    /// <param name="sender">The <see cref="IHierarchyObject"/> that exited the hierarchy.</param>
-    /// <param name="gameManager">The <see cref="IGameManager"/> that the <see cref="IHierarchyObject"/> has exited it's hierarchy.</param>
-    delegate void ExitedHierarchyEventHandler(IHierarchyObject sender, IGameManager gameManager);
-
-    /// <summary>
-    /// Delegate for the event triggered when the <see cref="IHierarchyObject"/>'s parent changes.
-    /// </summary>
-    /// <param name="sender">The <see cref="IHierarchyObject"/> that the parent has changed.</param>
-    /// <param name="previousParent">The previous <see cref="IHierarchyObject"/> the sender was a child of.</param>
-    /// <param name="newParent">The new and current <see cref="IHierarchyObject"/> the sender is a child of.</param>
-    delegate void ParentChangedEventHandler(IHierarchyObject sender, IHierarchyObject? previousParent, IHierarchyObject? newParent);
-
-    /// <summary>
-    /// Delegate for the event triggered when a new <see cref="IHierarchyObject"/> added as a child.
-    /// </summary>
-    /// <param name="sender">The parent <see cref="IHierarchyObject"/> this event is being called from.</param>
-    /// <param name="childrenAdded">The <see cref="IHierarchyObject"/> that got removed as a children of the sender <see cref="IHierarchyObject"/>.</param>
-    delegate void ChildrenAddedEventHandler(IHierarchyObject sender, IHierarchyObject childrenAdded);
-
-    /// <summary>
-    /// Delegate for the event triggered when a new <see cref="IHierarchyObject"/> removed from being a child.
-    /// </summary>
-    /// <param name="sender">The parent <see cref="IHierarchyObject"/> this event is being called from.</param>
-    /// <param name="childrenAdded">The <see cref="IHierarchyObject"/> that got removed as a children of the sender <see cref="IHierarchyObject"/>.</param>
-    delegate void ChildrenRemovedEventHandler(IHierarchyObject sender, IHierarchyObject childrenRemoved);
-}

Engine.Core/Abstract/IInitializable.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents an entity that can be initialized and finalized. This information is useful for objects we know that are not in use and can be either recycled or dropped for garbage collection.
@@ -8,12 +8,12 @@ public interface IInitializable
     /// <summary>
     /// Event triggered when the <see cref="Initialize"/> method is called successfully.
     /// </summary>
-    event InitializedEventHandler? OnInitialized;
+    Event<IInitializable> OnInitialized { get; }
 
     /// <summary>
     /// Event triggered when the <see cref="IInitializable"/> method is called successfully.
     /// </summary>
-    event FinalizedEventHandler? OnFinalized;
+    Event<IInitializable> OnFinalized { get; }
 
     /// <summary>
     /// The value indicating whether the entity has been initialized.
@@ -31,7 +31,4 @@ public interface IInitializable
     /// </summary>
     /// <returns><see cref="true"/> if finalization is successful, otherwise <see cref="false"/>.</returns>
     bool Finalize();
-
-    delegate void InitializedEventHandler(IInitializable sender);
-    delegate void FinalizedEventHandler(IInitializable sender);
 }

Engine.Core/Abstract/INameable.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents an entity with a name.
@@ -8,12 +8,12 @@ public interface INameable
     /// <summary>
     /// Event triggered when the name of the entity changes.
     /// </summary>
-    event NameChangedEventHandler? OnNameChanged;
+    Event<INameable, NameChangedArguments> OnNameChanged { get; }
 
     /// <summary>
     /// The name of the entity.
     /// </summary>
     string Name { get; set; }
 
-    delegate void NameChangedEventHandler(INameable sender, string previousName);
+    readonly record struct NameChangedArguments(string PreviousName);
 }

Engine.Core/Abstract/IStateEnable.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents an entity with an enable state that can be toggled.
@@ -8,12 +8,12 @@ public interface IStateEnable : IHasEntity
     /// <summary>
     /// Event triggered when the <see cref="Enabled"/> state of the <see cref="IStateEnable"/> changes.
     /// </summary>
-    event EnabledChangedEventHandler? OnEnabledChanged;
+    Event<IStateEnable, EnabledChangedArguments> OnEnabledChanged { get; }
 
     /// <summary>
     /// The value indicating whether the <see cref="IStateEnable"/> is enabled.
     /// </summary>
     bool Enabled { get; set; }
 
-    delegate void EnabledChangedEventHandler(IStateEnable sender, bool previousState);
+    readonly record struct EnabledChangedArguments(bool PreviousState);
 }

Engine.Core/Abstract/ITransform2D.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 /// <summary>
 /// Represents the transformation properties of an object such as position, scale, and rotation in 2D space.
@@ -8,17 +8,42 @@ public interface ITransform2D : IBehaviour
     /// <summary>
     /// Event triggered when the <see cref="Position"/> of the <see cref="ITransform2D"/> changes.
     /// </summary>
-    event PositionChangedEventHandler? OnPositionChanged;
+    Event<ITransform2D, PositionChangedArguments> OnPositionChanged { get; }
 
     /// <summary>
     /// Event triggered when the <see cref="Scale"/> of the <see cref="ITransform2D"/> changes.
     /// </summary>
-    event ScaleChangedEventHandler? OnScaleChanged;
+    Event<ITransform2D, ScaleChangedArguments> OnScaleChanged { get; }
 
     /// <summary>
-    /// Event triggered when the <see cref="Rotation"/> of the <see cref="ITransform"/> changes.
+    /// Event triggered when the <see cref="Rotation"/> of the <see cref="ITransform2D"/> changes.
     /// </summary>
-    event RotationChangedEventHandler? OnRotationChanged;
+    Event<ITransform2D, RotationChangedArguments> OnRotationChanged { get; }
+
+    /// <summary>
+    /// Event triggered when any of the properties of the <see cref="ITransform2D"/> gets updated.
+    /// </summary>
+    Event<ITransform2D> OnTransformUpdated { get; }
+
+    /// <summary>
+    /// The <see cref="Vector2D"/> pointing upwards in world space.
+    /// </summary>
+    Vector2D Up { get; }
+
+    /// <summary>
+    /// The <see cref="Vector2D"/> pointing upwards in world space.
+    /// </summary>
+    Vector2D Down { get; }
+
+    /// <summary>
+    /// The <see cref="Vector2D"/> pointing upwards in world space.
+    /// </summary>
+    Vector2D Left { get; }
+
+    /// <summary>
+    /// The <see cref="Vector2D"/> pointing upwards in world space.
+    /// </summary>
+    Vector2D Right { get; }
 
     /// <summary>
     /// The world position of the <see cref="ITransform2D"/> in 2D space.
@@ -51,23 +76,20 @@ public interface ITransform2D : IBehaviour
     float LocalRotation { get; set; }
 
     /// <summary>
-    /// Delegate for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
+    /// Arguments for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
     /// </summary>
-    /// <param name="sender">The <see cref="ITransform2D"/> that the parent has changed.</param>
+    /// <param name="PreviousPosition">The previous <see cref="Position"/> of the <see cref="ITransform2D"/>.</param>
-    /// <param name="previousPosition">The previous <see cref="Position"/> of the <see cref="ITransform2D"/>.</param>
+    readonly record struct PositionChangedArguments(Vector2D PreviousPosition);
-    delegate void PositionChangedEventHandler(ITransform2D sender, Vector2D previousPosition);
 
     /// <summary>
-    /// Delegate for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
+    /// Arguments for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
     /// </summary>
-    /// <param name="sender">The <see cref="ITransform2D"/> that the parent has changed.</param>
+    /// <param name="PreviousScale">The previous <see cref="Scale"/> of the <see cref="ITransform2D"/>.</param>
-    /// <param name="previousScale">The previous <see cref="Scale"/> of the <see cref="ITransform2D"/>.</param>
+    readonly record struct ScaleChangedArguments(Vector2D PreviousScale);
-    delegate void ScaleChangedEventHandler(ITransform2D sender, Vector2D previousScale);
 
     /// <summary>
-    /// Delegate for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
+    /// Arguments for the event triggered when the <see cref="ITransform2D"/>'s rotation changes.
     /// </summary>
-    /// <param name="sender">The <see cref="ITransform2D"/> that the parent has changed.</param>
+    /// <param name="PreviousRotation">The previous <see cref="Rotation"/> of the <see cref="ITransform2D"/>.</param>
-    /// <param name="previousRotation">The previous <see cref="Rotation"/> of the <see cref="ITransform2D"/>.</param>
+    readonly record struct RotationChangedArguments(float PreviousRotation);
-    delegate void RotationChangedEventHandler(ITransform2D sender, float previousRotation);
 }

Engine.Core/Abstract/ITransform3D.cs

@@ -0,0 +1,105 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Represents the transformation properties of an object such as position, scale, and rotation in 3D space.
+/// </summary>
+public interface ITransform3D : IBehaviour
+{
+    /// <summary>
+    /// Event triggered when the <see cref="Position"/> of the <see cref="ITransform3D"/> changes.
+    /// </summary>
+    Event<ITransform3D, PositionChangedArguments> OnPositionChanged { get; }
+
+    /// <summary>
+    /// Event triggered when the <see cref="Scale"/> of the <see cref="ITransform3D"/> changes.
+    /// </summary>
+    Event<ITransform3D, ScaleChangedArguments> OnScaleChanged { get; }
+
+    /// <summary>
+    /// Event triggered when the <see cref="Rotation"/> of the <see cref="ITransform3D"/> changes.
+    /// </summary>
+    Event<ITransform3D, RotationChangedArguments> OnRotationChanged { get; }
+
+    /// <summary>
+    /// Event triggered when any of the properties of the <see cref="ITransform3D"/> gets updated.
+    /// </summary>
+    Event<ITransform3D> OnTransformUpdated { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing upwards in world space.
+    /// </summary>
+    Vector3D Up { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing upwards in world space.
+    /// </summary>
+    Vector3D Down { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing upwards in world space.
+    /// </summary>
+    Vector3D Left { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing upwards in world space.
+    /// </summary>
+    Vector3D Right { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing forwards in world space.
+    /// </summary>
+    Vector3D Forward { get; }
+
+    /// <summary>
+    /// The <see cref="Vector3D"/> pointing backwards in world space.
+    /// </summary>
+    Vector3D Backward { get; }
+
+    /// <summary>
+    /// The world position of the <see cref="ITransform3D"/> in 3D space.
+    /// </summary>
+    Vector3D Position { get; set; }
+
+    /// <summary>
+    /// The world scale of the <see cref="ITransform3D"/>.
+    /// </summary>
+    Vector3D Scale { get; set; }
+
+    /// <summary>
+    /// The world rotation of the <see cref="ITransform3D"/> in degrees.
+    /// </summary>
+    Quaternion Rotation { get; set; }
+
+    /// <summary>
+    /// The local position of the <see cref="ITransform3D"/> in 3D space.
+    /// </summary>
+    Vector3D LocalPosition { get; set; }
+
+    /// <summary>
+    /// The local scale of the <see cref="ITransform3D"/>.
+    /// </summary>
+    Vector3D LocalScale { get; set; }
+
+    /// <summary>
+    /// The local rotation of the <see cref="ITransform3D"/> in degrees.
+    /// </summary>
+    Quaternion LocalRotation { get; set; }
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="ITransform3D"/>'s rotation changes.
+    /// </summary>
+    /// <param name="PreviousPosition">The previous <see cref="Position"/> of the <see cref="ITransform3D"/>.</param>
+    readonly record struct PositionChangedArguments(Vector3D PreviousPosition);
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="ITransform3D"/>'s rotation changes.
+    /// </summary>
+    /// <param name="PreviousScale">The previous <see cref="Scale"/> of the <see cref="ITransform3D"/>.</param>
+    readonly record struct ScaleChangedArguments(Vector3D PreviousScale);
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="ITransform3D"/>'s rotation changes.
+    /// </summary>
+    /// <param name="PreviousRotation">The previous <see cref="Rotation"/> of the <see cref="ITransform3D"/>.</param>
+    readonly record struct RotationChangedArguments(Quaternion PreviousRotation);
+}

Engine.Core/Abstract/IUniverse.cs

@@ -0,0 +1,120 @@
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+/// <summary>
+/// Represents a universe responsible for managing <see cref="IUniverseObject"/>s.
+/// </summary>
+public interface IUniverse : IEntity, IEnumerable<IUniverseObject>
+{
+    /// <summary>
+    /// Event triggered when <see cref="Update(UniverseTime)"/> is about to be called called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UpdateArguments> OnPreUpdate { get; }
+
+    /// <summary>
+    /// Event triggered when <see cref="Update(UniverseTime)"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UpdateArguments> OnUpdate { get; }
+
+    /// <summary>
+    /// Event triggered after <see cref="Update(UniverseTime)"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UpdateArguments> OnPostUpdate { get; }
+
+    /// <summary>
+    /// Event triggered when <see cref="Draw"/> is about to be called called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse> OnPreDraw { get; }
+
+    /// <summary>
+    /// Event triggered when <see cref="Draw"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse> OnDraw { get; }
+
+    /// <summary>
+    /// Event triggered after <see cref="Draw"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse> OnPostDraw { get; }
+
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is about to be registered to the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectRegisteredArguments> OnPreUniverseObjectRegistered { get; }
+
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is registered to the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectRegisteredArguments> OnUniverseObjectRegistered { get; }
+
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is about to be unregistered from the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectUnRegisteredArguments> OnPreUniverseObjectUnRegistered { get; }
+
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is unregistered from the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectUnRegisteredArguments> OnUniverseObjectUnRegistered { get; }
+
+    /// <summary>
+    /// Event triggered when <see cref="TimeScale"/> is changed on the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, TimeScaleChangedArguments> OnTimeScaleChanged { get; }
+
+    /// <summary>
+    /// Current time scale the <see cref="IUniverse"/> operates on.
+    /// </summary>
+    float TimeScale { get; set; }
+
+    /// <summary>
+    /// Contains time data related to this <see cref="IUniverse"/>.
+    /// </summary>
+    UniverseTime Time { get; }
+
+    /// <summary>
+    /// Contains unscaled time data related to this <see cref="IUniverse"/>.
+    /// </summary>
+    UniverseTime UnscaledTime { get; }
+
+    /// <summary>
+    /// Gets the root <see cref="IUniverseObject"/> of the <see cref="IUniverse"/>.
+    /// </summary>
+    IUniverseObject Root { get; }
+
+    /// <summary>
+    /// Registers an <see cref="IUniverseObject"/> to the <see cref="IUniverse"/>.
+    /// </summary>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to register.</param>
+    void Register(IUniverseObject universeObject);
+
+    /// <summary>
+    /// Instantiates a <see cref="IUniverseObject"/> of type T with the given arguments and registers it to the <see cref="IUniverse"/>.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to instantiate.</typeparam>
+    /// <param name="args">Constructor parameters for the given type of <see cref="IUniverseObject"/>.</param>
+    /// <returns>The instantiated <see cref="IUniverseObject"/>.</returns>
+    T InstantiateUniverseObject<T>(params object?[]? args) where T : class, IUniverseObject;
+
+    /// <summary>
+    /// Removes an <see cref="IUniverseObject"/> from the <see cref="IUniverse"/>.
+    /// </summary>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to remove.</param>
+    void Remove(IUniverseObject universeObject);
+
+    /// <summary>
+    /// Updates the <see cref="IUniverse"/> with the given delta time.
+    /// </summary>
+    /// <param name="universeTime">Delta time.</param>
+    void Update(UniverseTime universeTime);
+
+    /// <summary>
+    /// Performs operations that should be done to the draw.
+    /// </summary>
+    void Draw();
+
+    readonly record struct TimeScaleChangedArguments(float PreviousTimeScale);
+    readonly record struct UpdateArguments(UniverseTime EngineTime);
+    readonly record struct UniverseObjectRegisteredArguments(IUniverseObject UniverseObjectRegistered);
+    readonly record struct UniverseObjectUnRegisteredArguments(IUniverseObject UniverseObjectUnregistered);
+}

Engine.Core/Abstract/IUniverseObject.cs

@@ -0,0 +1,125 @@
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+/// <summary>
+/// Represents an <see cref="IEntity"/> that can enter and exit a universe within the <see cref="IUniverse"/> system.
+/// This interface allows for tracking the object's presence in the universe and provides events 
+/// for notifying when the see enters or exits the universe.
+/// </summary>
+public interface IUniverseObject : IEntity, IActive, INameable, IHasBehaviourController
+{
+    /// <summary>
+    /// Event triggered when the <see cref="IUniverseObject"/> enters the universe.
+    /// </summary>
+    Event<IUniverseObject, EnteredUniverseArguments> OnEnteredUniverse { get; }
+
+    /// <summary>
+    /// Event triggered when the <see cref="IUniverseObject"/> exits the universe.
+    /// </summary>
+    Event<IUniverseObject, ExitedUniverseArguments> OnExitedUniverse { get; }
+
+    /// <summary>
+    /// Event triggered when the <see cref="Parent"/> of the <see cref="IUniverseObject"/> changes. The second parameter is the old <see cref="IUniverseObject"/>.
+    /// </summary>
+    Event<IUniverseObject, ParentChangedArguments> OnParentChanged { get; }
+
+    /// <summary>
+    /// Event triggered when a new <see cref="IUniverseObject"/> is added to the <see cref="Children"/>.
+    /// </summary>
+    Event<IUniverseObject, ChildrenAddedArguments> OnChildrenAdded { get; }
+
+    /// <summary>
+    /// Event triggered when an <see cref="IUniverseObject"/> is removed from the <see cref="Children"/>.
+    /// </summary>
+    Event<IUniverseObject, ChildrenRemovedArguments> OnChildrenRemoved { get; }
+
+    /// <summary>
+    /// Gets the <see cref="IUniverse"/> this <see cref="IUniverseObject"/> is connected to, if any.
+    /// </summary>
+    IUniverse Universe { get; }
+
+    /// <summary>
+    /// Indicates whether the <see cref="IUniverseObject"/> is currently in the universe.
+    /// </summary>
+    bool IsInUniverse { get; }
+
+    /// <summary>
+    /// The parent <see cref="IUniverseObject"/> of the <see cref="IUniverseObject"/>.
+    /// </summary>
+    IUniverseObject? Parent { get; set; }
+
+    /// <summary>
+    /// The <see cref="IUniverseObject"/>s that have this <see cref="IUniverseObject"/> as their <see cref="Parent"/>.
+    /// </summary>
+    IReadOnlyList<IUniverseObject> Children { get; }
+
+    /// <summary>
+    /// Internal method to handle entering the universe.
+    /// This should be called by the system to properly manage universe states.
+    /// </summary>
+    /// <param name="universe">The <see cref="IUniverse"/> that is managing this universe.</param>
+    /// <returns>
+    /// <see cref="true"/> if the <see cref="IUniverseObject"/> successfully entered the universe; 
+    /// <see cref="false"/> if it failed to do so.
+    /// </returns>
+    internal bool EnterUniverse(IUniverse universe);
+
+    /// <summary>
+    /// Internal method to handle exiting the universe.
+    /// This should be called by the system to properly manage universe states.
+    /// </summary>
+    /// <returns>
+    /// <see cref="true"/> if the <see cref="IUniverseObject"/> successfully exited the universe; 
+    /// <see cref="false"/> if it failed to do so.
+    /// </returns>
+    internal bool ExitUniverse();
+
+    /// <summary>
+    /// Adds a child <see cref="IUniverseObject"/> to this <see cref="IUniverseObject"/>.
+    /// </summary>
+    /// <param name="universeObject">The child <see cref="IUniverseObject"/> to add.</param>
+    void AddChild(IUniverseObject universeObject);
+
+    /// <summary>
+    /// Removes a child <see cref="IUniverseObject"/> from this <see cref="IUniverseObject"/>.
+    /// </summary>
+    /// <param name="universeObject">The child <see cref="IUniverseObject"/> to remove.</param>
+    void RemoveChild(IUniverseObject universeObject);
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="IUniverseObject"/> enters the universe of a <see cref="IUniverse">.
+    /// </summary>
+    /// <param name="sender">The <see cref="IUniverseObject"/> that entered the universe.</param>
+    /// <param name="universe">The <see cref="IUniverse"/> that the <see cref="IUniverseObject"/> has entered it's universe.</param>
+    readonly record struct EnteredUniverseArguments(IUniverse Universe);
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="IUniverseObject"/> exits the universe of a <see cref="IUniverse">.
+    /// </summary>
+    /// <param name="sender">The <see cref="IUniverseObject"/> that exited the universe.</param>
+    /// <param name="universe">The <see cref="IUniverse"/> that the <see cref="IUniverseObject"/> has exited it's universe.</param>
+    readonly record struct ExitedUniverseArguments(IUniverse Universe);
+
+    /// <summary>
+    /// Arguments for the event triggered when the <see cref="IUniverseObject"/>'s parent changes.
+    /// </summary>
+    /// <param name="sender">The <see cref="IUniverseObject"/> that the parent has changed.</param>
+    /// <param name="previousParent">The previous <see cref="IUniverseObject"/> the sender was a child of.</param>
+    /// <param name="newParent">The new and current <see cref="IUniverseObject"/> the sender is a child of.</param>
+    readonly record struct ParentChangedArguments(IUniverseObject? PreviousParent, IUniverseObject? CurrentParent);
+
+    /// <summary>
+    /// Arguments for the event triggered when a new <see cref="IUniverseObject"/> added as a child.
+    /// </summary>
+    /// <param name="sender">The parent <see cref="IUniverseObject"/> this event is being called from.</param>
+    /// <param name="childrenAdded">The <see cref="IUniverseObject"/> that got removed as a children of the sender <see cref="IUniverseObject"/>.</param>
+    readonly record struct ChildrenAddedArguments(IUniverseObject ChildrenAdded);
+
+    /// <summary>
+    /// Delegate for the event triggered when a new <see cref="IUniverseObject"/> removed from being a child.
+    /// </summary>
+    /// <param name="sender">The parent <see cref="IUniverseObject"/> this event is being called from.</param>
+    /// <param name="childrenAdded">The <see cref="IUniverseObject"/> that got removed as a children of the sender <see cref="IUniverseObject"/>.</param>
+    readonly record struct ChildrenRemovedArguments(IUniverseObject ChildrenRemoved);
+}

Engine.Core/ActiveBehaviourCollector.cs

@@ -1,127 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public class ActiveBehaviourCollector<T> : IBehaviourCollector<T> where T : class, IBehaviour
-{
-    public event IAssignable.UnassignEventHandler? OnUnassigned = null;
-    public event IHasGameManager.GameManagerAssignedEventHandler? OnGameManagerAssigned = null;
-
-    public event IBehaviourCollector<T>.CollectedEventHandler? OnCollected = null;
-    public event IBehaviourCollector<T>.RemovedEventHandler? OnRemoved = null;
-
-    private readonly List<T> monitoringBehaviours = new(32);
-    protected readonly List<T> activeBehaviours = new(32);
-    protected readonly Dictionary<IActive, T> monitoringActiveToBehaviour = new(32);
-
-    public IReadOnlyList<T> Behaviours => activeBehaviours;
-    public IGameManager GameManager { get; private set; } = null!;
-
-    public T this[Index index] => activeBehaviours[index];
-
-    public ActiveBehaviourCollector() { }
-    public ActiveBehaviourCollector(IGameManager gameManager) => Assign(gameManager);
-
-    private void OnHierarchyObjectRegistered(IGameManager manager, IHierarchyObject hierarchyObject)
-    {
-        hierarchyObject.BehaviourController.OnBehaviourAdded += OnBehaviourAdded;
-        hierarchyObject.BehaviourController.OnBehaviourRemoved += OnBehaviourRemoved;
-
-        foreach (IBehaviour item in hierarchyObject.BehaviourController)
-            OnBehaviourAdded(hierarchyObject.BehaviourController, item);
-    }
-
-    private void OnHierarchyObjectUnregistered(IGameManager manager, IHierarchyObject hierarchyObject)
-    {
-        hierarchyObject.BehaviourController.OnBehaviourAdded -= OnBehaviourAdded;
-        hierarchyObject.BehaviourController.OnBehaviourRemoved -= OnBehaviourRemoved;
-
-        foreach (IBehaviour item in hierarchyObject.BehaviourController)
-            OnBehaviourRemoved(hierarchyObject.BehaviourController, item);
-    }
-
-    protected virtual void OnBehaviourAdd(IBehaviour behaviour) { }
-    private void OnBehaviourAdded(IBehaviourController controller, IBehaviour behaviour)
-    {
-        if (behaviour is not T tBehaviour)
-            return;
-
-        monitoringBehaviours.Add(tBehaviour);
-        monitoringActiveToBehaviour.Add(tBehaviour, tBehaviour);
-        tBehaviour.OnActiveChanged += OnBehaviourStateChanged;
-        OnBehaviourStateChanged(tBehaviour, !tBehaviour.IsActive);
-    }
-
-    private void OnBehaviourStateChanged(IActive sender, bool previousState)
-    {
-        T behaviour = monitoringActiveToBehaviour[sender];
-        if (sender.IsActive)
-        {
-            activeBehaviours.Add(behaviour);
-            OnBehaviourAdd(behaviour);
-            OnCollected?.Invoke(this, behaviour);
-        }
-        else if (activeBehaviours.Remove(behaviour))
-        {
-            OnBehaviourRemove(behaviour);
-            OnRemoved?.Invoke(this, behaviour);
-        }
-    }
-
-    protected virtual void OnBehaviourRemove(IBehaviour behaviour) { }
-    private void OnBehaviourRemoved(IBehaviourController controller, IBehaviour behaviour)
-    {
-        if (behaviour is not T tBehaviour)
-            return;
-
-        if (!monitoringBehaviours.Remove(tBehaviour) || !monitoringActiveToBehaviour.Remove(tBehaviour))
-            return;
-
-        tBehaviour.OnActiveChanged -= OnBehaviourStateChanged;
-        if (activeBehaviours.Remove(tBehaviour))
-        {
-            OnBehaviourRemove(tBehaviour);
-            OnRemoved?.Invoke(this, tBehaviour);
-        }
-    }
-
-    public bool Assign(IGameManager gameManager)
-    {
-        if (GameManager is not null)
-            return false;
-
-        foreach (IHierarchyObject hierarchyObject in gameManager.HierarchyObjects)
-            OnHierarchyObjectRegistered(gameManager, hierarchyObject);
-
-        gameManager.OnHierarchyObjectRegistered += OnHierarchyObjectRegistered;
-        gameManager.OnHierarchyObjectUnRegistered += OnHierarchyObjectUnregistered;
-
-        GameManager = gameManager;
-        OnGameManagerAssigned?.Invoke(this);
-
-        return true;
-    }
-
-    public bool Unassign()
-    {
-        if (GameManager is null)
-            return false;
-
-        foreach (IHierarchyObject hierarchyObject in GameManager.HierarchyObjects)
-            OnHierarchyObjectUnregistered(GameManager, hierarchyObject);
-
-        GameManager.OnHierarchyObjectRegistered -= OnHierarchyObjectRegistered;
-        GameManager.OnHierarchyObjectUnRegistered -= OnHierarchyObjectUnregistered;
-
-        GameManager = null!;
-        OnUnassigned?.Invoke(this);
-        return true;
-    }
-
-    public IEnumerator<T> GetEnumerator() => activeBehaviours.GetEnumerator();
-    IEnumerator IEnumerable.GetEnumerator() => activeBehaviours.GetEnumerator();
-}

Engine.Core/ActiveBehaviourCollectorSorted.cs

@@ -1,30 +0,0 @@
-using System;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public class ActiveBehaviourCollectorSorted<T> : ActiveBehaviourCollector<T> where T : class, IBehaviour
-{
-    private Comparison<T>? _sortBy = null;
-    public Comparison<T>? SortBy
-    {
-        get => _sortBy;
-        set
-        {
-            _sortBy = value;
-
-            if (value is not null)
-                activeBehaviours.Sort(value);
-        }
-    }
-
-    protected override void OnBehaviourAdd(IBehaviour behaviour)
-    {
-        if (SortBy is not null)
-            activeBehaviours.Sort(SortBy);
-    }
-
-    public ActiveBehaviourCollectorSorted() { }
-    public ActiveBehaviourCollectorSorted(IGameManager gameManager, Comparison<T> sortBy) : base(gameManager) => SortBy = sortBy;
-}

Engine.Core/BaseEntity.cs

@@ -1,16 +1,14 @@
 using System;
 
-namespace Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
 public abstract class BaseEntity : IEntity
 {
-    public event IEntity.IdChangedEventHandler? OnIdChanged = null;
+    public Event<IIdentifiable, IIdentifiable.IdChangedArguments> OnIdChanged { get; } = new();
-
+    public Event<IInitializable> OnInitialized { get; } = new();
-    public event IInitializable.InitializedEventHandler? OnInitialized = null;
+    public Event<IInitializable> OnFinalized { get; } = new();
-    public event IInitializable.FinalizedEventHandler? OnFinalized = null;
+    public Event<IHasStateEnable> OnStateEnableAssigned { get; } = new();
-
+    public Event<IAssignable> OnUnassigned { get; } = new();
-    public event IHasStateEnable.StateEnableAssignedEventHandler? OnStateEnableAssigned = null;
-    public event IAssignable.UnassignEventHandler? OnUnassigned = null;
 
     private IStateEnable _stateEnable = null!;
 
@@ -33,7 +31,7 @@ public abstract class BaseEntity : IEntity
             string previousId = _id;
 
             _id = value;
-            OnIdChanged?.Invoke(this, previousId);
+            OnIdChanged?.Invoke(this, new(previousId));
         }
     }
 

Engine.Core/Behaviour.cs

@@ -1,105 +1,103 @@
-using Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
-namespace Syntriax.Engine.Core;
+[System.Diagnostics.DebuggerDisplay("{GetType().Name, nq}, Priority: {Priority}, Initialized: {Initialized}")]
-
+public abstract class Behaviour : BaseEntity, IBehaviour
-public abstract class Behaviour : BehaviourBase
 {
-    private bool isInitializedThisFrame = false;
+    public Event<IBehaviour, IBehaviour.PriorityChangedArguments> OnPriorityChanged { get; } = new();
+    public Event<IActive, IActive.ActiveChangedArguments> OnActiveChanged { get; } = new();
+    public Event<IHasBehaviourController> OnBehaviourControllerAssigned { get; } = new();
 
-    protected IGameManager GameManager => BehaviourController.HierarchyObject.GameManager;
+    private readonly Event<IHasUniverseObject>.EventHandler delegateOnUniverseObjectAssigned = null!;
-    protected IHierarchyObject HierarchyObject => BehaviourController.HierarchyObject;
+    private readonly Event<IActive, IActive.ActiveChangedArguments>.EventHandler delegateOnUniverseObjectActiveChanged = null!;
+    private readonly Event<IStateEnable, IStateEnable.EnabledChangedArguments>.EventHandler delegateOnStateEnabledChanged = null!;
 
-    public Behaviour()
+    public IUniverse Universe => BehaviourController.UniverseObject.Universe;
+    public IUniverseObject UniverseObject => BehaviourController.UniverseObject;
+
+    private IBehaviourController _behaviourController = null!;
+    public IBehaviourController BehaviourController => _behaviourController;
+
+    private int _priority = 0;
+    public int Priority
     {
-        OnInitialized += OnInitialize;
+        get => _priority;
-        OnFinalized += OnFinalize;
+        set
-        OnUnassigned += OnUnassign;
-    }
-
-    protected virtual void OnUnassign() { }
-    protected virtual void OnUnassign(IAssignable assignable) => OnUnassign();
-
-    protected virtual void OnInitialize() { }
-    protected virtual void OnInitialize(IInitializable _)
         {
-        isInitializedThisFrame = true;
+            if (value == _priority)
-
-        BehaviourController.OnPreUpdate += PreUpdate;
-        BehaviourController.OnPreDraw += PreDraw;
-        BehaviourController.OnUpdate += Update;
-        BehaviourController.HierarchyObject.OnEnteredHierarchy += EnteredHierarchy;
-        BehaviourController.HierarchyObject.OnExitedHierarchy += ExitedHierarchy;
-
-        OnInitialize();
-
-        if (HierarchyObject.IsInHierarchy)
-            EnteredHierarchy(HierarchyObject, GameManager);
-    }
-
-    protected virtual void OnFinalize() { }
-    protected virtual void OnFinalize(IInitializable _)
-    {
-        BehaviourController.OnPreUpdate -= PreUpdate;
-        BehaviourController.OnPreDraw -= PreDraw;
-        BehaviourController.OnUpdate -= Update;
-        BehaviourController.HierarchyObject.OnEnteredHierarchy -= EnteredHierarchy;
-        BehaviourController.HierarchyObject.OnExitedHierarchy -= ExitedHierarchy;
-
-        OnFinalize();
-
-        if (HierarchyObject.IsInHierarchy)
-            ExitedHierarchy(HierarchyObject, GameManager);
-    }
-
-    protected virtual void OnPreUpdatePreActiveCheck() { }
-    protected virtual void OnPreUpdate() { }
-    protected virtual void PreUpdate(IBehaviourController _)
-    {
-        OnPreUpdatePreActiveCheck();
-
-        if (!IsActive)
                 return;
 
-        if (isInitializedThisFrame)
+            int previousPriority = _priority;
-            FirstActiveFrame();
+            _priority = value;
-
+            OnPriorityChanged?.Invoke(this, new(previousPriority));
-        OnPreUpdate();
+        }
     }
 
-    protected virtual void OnFirstActiveFrame() { }
+    private bool _isActive = false;
-    protected virtual void FirstActiveFrame()
+    public bool IsActive => _isActive;
+
+    protected virtual void OnAssign(IBehaviourController behaviourController) { }
+    public bool Assign(IBehaviourController behaviourController)
     {
-        OnFirstActiveFrame();
+        if (IsInitialized)
-        isInitializedThisFrame = false;
+            return false;
+
+        _behaviourController = behaviourController;
+        OnAssign(behaviourController);
+        behaviourController.OnUniverseObjectAssigned.AddListener(delegateOnUniverseObjectAssigned);
+        behaviourController.StateEnable.OnEnabledChanged.AddListener(delegateOnStateEnabledChanged);
+        if (behaviourController.UniverseObject is not null)
+            OnUniverseObjectAssigned(behaviourController);
+        OnBehaviourControllerAssigned?.Invoke(this);
+        return true;
     }
 
-    protected virtual void OnUpdatePreActiveCheck() { }
+    private void OnUniverseObjectAssigned(IHasUniverseObject sender)
-    protected virtual void OnUpdate() { }
-    protected virtual void Update(IBehaviourController _)
     {
-        OnUpdatePreActiveCheck();
+        sender.UniverseObject.OnActiveChanged.AddListener(delegateOnUniverseObjectActiveChanged);
-
+        UpdateActive();
-        if (!IsActive)
-            return;
-
-        OnUpdate();
     }
 
-    protected virtual void OnPreDrawPreActiveCheck() { }
+    protected override void OnAssign(IStateEnable stateEnable)
-    protected virtual void OnPreDraw() { }
-    protected virtual void PreDraw(IBehaviourController _)
     {
-        OnPreDrawPreActiveCheck();
+        base.OnAssign(stateEnable);
 
-        if (!StateEnable.Enabled)
+        stateEnable.OnEnabledChanged.AddListener(delegateOnStateEnabledChanged);
-            return;
-
-        OnPreDraw();
     }
 
-    protected virtual void OnEnteredHierarchy(IGameManager gameManager) { }
+    protected override void UnassignInternal()
-    protected virtual void EnteredHierarchy(IHierarchyObject sender, IGameManager gameManager) => OnEnteredHierarchy(gameManager);
+    {
-
+        BehaviourController.UniverseObject.OnActiveChanged.RemoveListener(delegateOnUniverseObjectActiveChanged);
-    protected virtual void OnExitedHierarchy(IGameManager gameManager) { }
+        StateEnable.OnEnabledChanged.RemoveListener(delegateOnStateEnabledChanged);
-    protected virtual void ExitedHierarchy(IHierarchyObject sender, IGameManager gameManager) => OnExitedHierarchy(gameManager);
+        BehaviourController.OnUniverseObjectAssigned.RemoveListener(delegateOnUniverseObjectAssigned);
+        BehaviourController.StateEnable.OnEnabledChanged.RemoveListener(delegateOnStateEnabledChanged);
+        base.UnassignInternal();
+        _behaviourController = null!;
+    }
+
+    protected override void InitializeInternal()
+    {
+        Debug.Assert.AssertBehaviourControllerAssigned(this);
+        Debug.Assert.AssertStateEnableAssigned(this);
+
+        UpdateActive();
+    }
+
+    private void OnStateEnabledChanged(IStateEnable sender, IStateEnable.EnabledChangedArguments args) => UpdateActive();
+    private void OnUniverseObjectActiveChanged(IActive sender, IActive.ActiveChangedArguments args) => UpdateActive();
+
+    private void UpdateActive()
+    {
+        bool previousActive = IsActive;
+        _isActive = StateEnable.Enabled && _behaviourController.StateEnable.Enabled && _behaviourController.UniverseObject.IsActive;
+
+        if (previousActive != IsActive)
+            OnActiveChanged?.Invoke(this, new(previousActive));
+    }
+
+    protected Behaviour()
+    {
+        delegateOnUniverseObjectAssigned = OnUniverseObjectAssigned;
+        delegateOnUniverseObjectActiveChanged = OnUniverseObjectActiveChanged;
+        delegateOnStateEnabledChanged = OnStateEnabledChanged;
+    }
 }

Engine.Core/Behaviour2D.cs

@@ -1,28 +1,10 @@
-using Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
 
-namespace Syntriax.Engine.Core;
+// TODO this should not use independent behaviour, the OnInitialize usage for getting the transform can cause very unexpected issues
-
+public abstract class Behaviour2D : Internal.BehaviourIndependent, IBehaviour2D
-public abstract class Behaviour2D : Behaviour, IBehaviour2D
 {
     public ITransform2D Transform { get; private set; } = null!;
 
-    protected sealed override void OnInitialize(IInitializable _)
+    protected override void OnInitialize() => Transform = BehaviourController.GetRequiredBehaviour<ITransform2D>();
-    {
+    protected override void OnFinalize() => Transform = null!;
-        Transform = BehaviourController.GetBehaviourInChildren<ITransform2D>() ?? throw new($"{HierarchyObject.Name} does not contain any {nameof(ITransform2D)}");
-        base.OnInitialize(_);
-    }
-
-    protected sealed override void OnFinalize(IInitializable _)
-    {
-        Transform = null!;
-        base.OnFinalize(_);
-    }
-
-    protected sealed override void OnUnassign(IAssignable assignable) => base.OnUnassign(assignable);
-    protected sealed override void PreUpdate(IBehaviourController behaviourController) => base.PreUpdate(behaviourController);
-    protected sealed override void FirstActiveFrame() => base.FirstActiveFrame();
-    protected sealed override void Update(IBehaviourController behaviourController) => base.Update(behaviourController);
-    protected sealed override void PreDraw(IBehaviourController behaviourController) => base.PreDraw(behaviourController);
-    protected sealed override void EnteredHierarchy(IHierarchyObject sender, IGameManager gameManager) => base.EnteredHierarchy(sender, gameManager);
-    protected sealed override void ExitedHierarchy(IHierarchyObject sender, IGameManager gameManager) => base.ExitedHierarchy(sender, gameManager);
 }

Engine.Core/BehaviourBase.cs

@@ -1,88 +0,0 @@
-using Syntriax.Engine.Core.Abstract;
-using Syntriax.Engine.Core.Exceptions;
-
-namespace Syntriax.Engine.Core;
-
-[System.Diagnostics.DebuggerDisplay("{GetType().Name, nq}, Priority: {Priority}, Initialized: {Initialized}")]
-public abstract class BehaviourBase : BaseEntity, IBehaviour
-{
-    public event IHasBehaviourController.BehaviourControllerAssignedEventHandler? OnBehaviourControllerAssigned = null;
-    public event IBehaviour.PriorityChangedEventHandler? OnPriorityChanged = null;
-    public event IActive.ActiveChangedEventHandler? OnActiveChanged = null;
-
-    private IBehaviourController _behaviourController = null!;
-    public IBehaviourController BehaviourController => _behaviourController;
-
-    private int _priority = 0;
-    public int Priority
-    {
-        get => _priority;
-        set
-        {
-            if (value == _priority)
-                return;
-
-            int previousPriority = _priority;
-            _priority = value;
-            OnPriorityChanged?.Invoke(this, previousPriority);
-        }
-    }
-
-    private bool _isActive = false;
-    public bool IsActive => _isActive;
-
-    protected virtual void OnAssign(IBehaviourController behaviourController) { }
-    public bool Assign(IBehaviourController behaviourController)
-    {
-        if (IsInitialized)
-            return false;
-
-        _behaviourController = behaviourController;
-        OnAssign(behaviourController);
-        behaviourController.OnHierarchyObjectAssigned += OnHierarchyObjectAssigned;
-        if (behaviourController.HierarchyObject is not null)
-            OnHierarchyObjectAssigned(behaviourController);
-        OnBehaviourControllerAssigned?.Invoke(this);
-        return true;
-    }
-
-    private void OnHierarchyObjectAssigned(IHasHierarchyObject sender)
-    {
-        sender.HierarchyObject.OnActiveChanged += OnHierarchyObjectActiveChanged;
-        UpdateActive();
-    }
-
-    protected override void OnAssign(IStateEnable stateEnable)
-    {
-        base.OnAssign(stateEnable);
-
-        stateEnable.OnEnabledChanged += OnStateEnabledChanged;
-    }
-
-    protected override void UnassignInternal()
-    {
-        StateEnable.OnEnabledChanged -= OnStateEnabledChanged;
-        BehaviourController.OnHierarchyObjectAssigned -= OnHierarchyObjectAssigned;
-        base.UnassignInternal();
-        _behaviourController = null!;
-    }
-
-    protected override void InitializeInternal()
-    {
-        base.InitializeInternal();
-        NotAssignedException.Check(this, _behaviourController);
-        NotAssignedException.Check(this, StateEnable);
-    }
-
-    private void OnStateEnabledChanged(IStateEnable sender, bool previousState) => UpdateActive();
-    private void OnHierarchyObjectActiveChanged(IActive sender, bool previousState) => UpdateActive();
-
-    private void UpdateActive()
-    {
-        bool previousActive = IsActive;
-        _isActive = StateEnable.Enabled && _behaviourController.HierarchyObject.IsActive;
-
-        if (previousActive != IsActive)
-            OnActiveChanged?.Invoke(this, previousActive);
-    }
-}

Engine.Core/BehaviourCollector.cs

@@ -1,106 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public class BehaviourCollector<T> : IBehaviourCollector<T> where T : class
-{
-    public event IAssignable.UnassignEventHandler? OnUnassigned = null;
-    public event IHasGameManager.GameManagerAssignedEventHandler? OnGameManagerAssigned = null;
-
-    public event IBehaviourCollector<T>.CollectedEventHandler? OnCollected = null;
-    public event IBehaviourCollector<T>.RemovedEventHandler? OnRemoved = null;
-
-    protected readonly List<T> behaviours = new(32);
-
-    public IReadOnlyList<T> Behaviours => behaviours;
-    public IGameManager GameManager { get; private set; } = null!;
-
-    public T this[Index index] => behaviours[index];
-
-    public BehaviourCollector() { }
-    public BehaviourCollector(IGameManager gameManager) => Assign(gameManager);
-
-    private void OnHierarchyObjectRegistered(IGameManager manager, IHierarchyObject hierarchyObject)
-    {
-        hierarchyObject.BehaviourController.OnBehaviourAdded += OnBehaviourAdded;
-        hierarchyObject.BehaviourController.OnBehaviourRemoved += OnBehaviourRemoved;
-
-        foreach (IBehaviour item in hierarchyObject.BehaviourController)
-            OnBehaviourAdded(hierarchyObject.BehaviourController, item);
-    }
-
-    private void OnHierarchyObjectUnregistered(IGameManager manager, IHierarchyObject hierarchyObject)
-    {
-        hierarchyObject.BehaviourController.OnBehaviourAdded -= OnBehaviourAdded;
-        hierarchyObject.BehaviourController.OnBehaviourRemoved -= OnBehaviourRemoved;
-
-        foreach (IBehaviour item in hierarchyObject.BehaviourController)
-            OnBehaviourRemoved(hierarchyObject.BehaviourController, item);
-    }
-
-    protected virtual void OnBehaviourAdd(IBehaviour behaviour) { }
-    private void OnBehaviourAdded(IBehaviourController controller, IBehaviour behaviour)
-    {
-        if (behaviour is not T tBehaviour)
-            return;
-
-        behaviours.Add(tBehaviour);
-        OnBehaviourAdd(behaviour);
-        OnCollected?.Invoke(this, tBehaviour);
-    }
-
-    protected virtual void OnBehaviourRemove(IBehaviour behaviour) { }
-    private void OnBehaviourRemoved(IBehaviourController controller, IBehaviour behaviour)
-    {
-        if (behaviour is not T tBehaviour)
-            return;
-
-        if (!behaviours.Remove(tBehaviour))
-            return;
-
-        OnBehaviourRemove(behaviour);
-        OnRemoved?.Invoke(this, tBehaviour);
-    }
-
-    protected virtual void OnAssign(IGameManager gameManager) { }
-    public bool Assign(IGameManager gameManager)
-    {
-        if (GameManager is not null)
-            return false;
-
-        foreach (IHierarchyObject hierarchyObject in gameManager.HierarchyObjects)
-            OnHierarchyObjectRegistered(gameManager, hierarchyObject);
-
-        gameManager.OnHierarchyObjectRegistered += OnHierarchyObjectRegistered;
-        gameManager.OnHierarchyObjectUnRegistered += OnHierarchyObjectUnregistered;
-
-        GameManager = gameManager;
-        OnAssign(gameManager);
-        OnGameManagerAssigned?.Invoke(this);
-
-        return true;
-    }
-
-    public bool Unassign()
-    {
-        if (GameManager is null)
-            return false;
-
-        foreach (IHierarchyObject hierarchyObject in GameManager.HierarchyObjects)
-            OnHierarchyObjectUnregistered(GameManager, hierarchyObject);
-
-        GameManager.OnHierarchyObjectRegistered -= OnHierarchyObjectRegistered;
-        GameManager.OnHierarchyObjectUnRegistered -= OnHierarchyObjectUnregistered;
-
-        GameManager = null!;
-        OnUnassigned?.Invoke(this);
-        return true;
-    }
-
-    public IEnumerator<T> GetEnumerator() => behaviours.GetEnumerator();
-    IEnumerator IEnumerable.GetEnumerator() => behaviours.GetEnumerator();
-}

Engine.Core/BehaviourCollectorSorted.cs

@@ -1,30 +0,0 @@
-using System;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public class BehaviourCollectorSorted<T> : BehaviourCollector<T> where T : class
-{
-    private Comparison<T>? _sortBy = null;
-    public Comparison<T>? SortBy
-    {
-        get => _sortBy;
-        set
-        {
-            _sortBy = value;
-
-            if (value is not null)
-                behaviours.Sort(value);
-        }
-    }
-
-    protected override void OnBehaviourAdd(IBehaviour behaviour)
-    {
-        if (SortBy is not null)
-            behaviours.Sort(SortBy);
-    }
-
-    public BehaviourCollectorSorted() { }
-    public BehaviourCollectorSorted(IGameManager gameManager, Comparison<T> sortBy) : base(gameManager) => SortBy = sortBy;
-}

Engine.Core/BehaviourController.cs

@@ -1,67 +1,42 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 
-using Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
-using Syntriax.Engine.Core.Exceptions;
-
-namespace Syntriax.Engine.Core;
 
 [System.Diagnostics.DebuggerDisplay("Behaviour Count: {behaviours.Count}")]
-public class BehaviourController : IBehaviourController
+public class BehaviourController : BaseEntity, IBehaviourController
 {
-    public event IBehaviourController.PreUpdateEventHandler? OnPreUpdate = null;
+    public Event<IBehaviourController, IBehaviourController.BehaviourAddedArguments> OnBehaviourAdded { get; } = new();
-    public event IBehaviourController.UpdateEventHandler? OnUpdate = null;
+    public Event<IBehaviourController, IBehaviourController.BehaviourRemovedArguments> OnBehaviourRemoved { get; } = new();
-    public event IBehaviourController.PreDrawEventHandler? OnPreDraw = null;
+    public Event<IHasUniverseObject> OnUniverseObjectAssigned { get; } = new();
 
-    public event IBehaviourController.BehaviourAddedEventHandler? OnBehaviourAdded = null;
+    private readonly FastList<IBehaviour> behaviours = new(Constants.BEHAVIOURS_SIZE_INITIAL);
-    public event IBehaviourController.BehaviourRemovedEventHandler? OnBehaviourRemoved = null;
-    public event IHasHierarchyObject.HierarchyObjectAssignedEventHandler? OnHierarchyObjectAssigned = null;
 
-    public event IInitializable.InitializedEventHandler? OnInitialized = null;
+    private IUniverseObject _universeObject = null!;
-    public event IInitializable.FinalizedEventHandler? OnFinalized = null;
 
-    public event IAssignable.UnassignEventHandler? OnUnassigned = null;
+    public IUniverseObject UniverseObject => _universeObject;
-
+    public int Count => behaviours.Count;
-    private readonly IList<IBehaviour> behaviours = new List<IBehaviour>(Constants.BEHAVIOURS_SIZE_INITIAL);
+    public IBehaviour this[Index index] => behaviours[index];
-
-    private IHierarchyObject _hierarchyObject = null!;
-    private bool _initialized = false;
-
-    public IHierarchyObject HierarchyObject => _hierarchyObject;
-
-    public bool IsInitialized
-    {
-        get => _initialized;
-        private set
-        {
-            if (value == _initialized)
-                return;
-
-            _initialized = value;
-            if (value)
-                OnInitialized?.Invoke(this);
-            else
-                OnFinalized?.Invoke(this);
-        }
-    }
 
     public T AddBehaviour<T>(T behaviour) where T : class, IBehaviour
     {
         InsertBehaviourByPriority(behaviour);
 
         behaviour.Assign(this);
-        behaviour.Assign(Factory.StateEnableFactory.Instantiate(behaviour));
 
+        if (IsInitialized)
             behaviour.Initialize();
-        behaviour.OnPriorityChanged += OnPriorityChange;
+
-        OnBehaviourAdded?.Invoke(this, behaviour);
+        behaviour.OnPriorityChanged.AddListener(OnPriorityChange);
+        OnBehaviourAdded?.Invoke(this, new(behaviour));
         return behaviour;
     }
 
     public T AddBehaviour<T>(params object?[]? args) where T : class, IBehaviour
-        => AddBehaviour(Factory.BehaviourFactory.Instantiate<T>(_hierarchyObject, args));
+    {
+        T behaviour = Factory.BehaviourFactory.Instantiate<T>(args);
+        return AddBehaviour(behaviour);
+    }
 
     public T? GetBehaviour<T>()
     {
@@ -72,24 +47,22 @@ public class BehaviourController : IBehaviourController
         return default;
     }
 
-    public IList<T> GetBehaviours<T>()
+    public IReadOnlyList<T> GetBehaviours<T>()
     {
-        List<T>? behaviours = null;
+        List<T> behaviours = [];
+
         foreach (IBehaviour behaviourItem in this.behaviours)
-        {
+            if (behaviourItem is T behaviour)
-            if (behaviourItem is not T behaviour)
-                continue;
-
-            behaviours ??= [];
                 behaviours.Add(behaviour);
+
+        return behaviours;
     }
 
-        return behaviours ?? Enumerable.Empty<T>().ToList();
+    public void GetBehaviours<T>(IList<T> results, IBehaviourController.CollectionMethod collectionMethod = IBehaviourController.CollectionMethod.Clear)
-    }
-
-    public void GetBehaviours<T>(IList<T> results)
     {
+        if (collectionMethod == IBehaviourController.CollectionMethod.Clear)
             results.Clear();
+
         foreach (IBehaviour behaviourItem in behaviours)
         {
             if (behaviourItem is not T behaviour)
@@ -101,7 +74,7 @@ public class BehaviourController : IBehaviourController
 
     public void RemoveBehaviour<T>(bool removeAll = false) where T : class, IBehaviour
     {
-        for (int i = behaviours.Count; i >= 0; i--)
+        for (int i = behaviours.Count - 1; i >= 0; i--)
         {
             if (behaviours[i] is not T behaviour)
                 continue;
@@ -116,81 +89,42 @@ public class BehaviourController : IBehaviourController
     public void RemoveBehaviour<T>(T behaviour) where T : class, IBehaviour
     {
         if (!behaviours.Contains(behaviour))
-            throw new Exception($"{behaviour.GetType().Name} does not exist in {HierarchyObject.Name}'s {nameof(IBehaviourController)}.");
+            throw new Exception($"{behaviour.GetType().Name} does not exist in {UniverseObject.Name}'s {nameof(IBehaviourController)}.");
 
-        behaviour.OnPriorityChanged -= OnPriorityChange;
+        behaviour.OnPriorityChanged.RemoveListener(OnPriorityChange);
         behaviour.Finalize();
         behaviours.Remove(behaviour);
-        OnBehaviourRemoved?.Invoke(this, behaviour);
+        OnBehaviourRemoved?.Invoke(this, new(behaviour));
     }
 
-    protected virtual void OnAssign(IHierarchyObject hierarchyObject) { }
+    protected virtual void OnAssign(IUniverseObject universeObject) { }
-    public bool Assign(IHierarchyObject hierarchyObject)
+    public bool Assign(IUniverseObject universeObject)
     {
-        if (HierarchyObject is not null && HierarchyObject.IsInitialized)
+        if (UniverseObject is not null && UniverseObject.IsInitialized)
             return false;
 
-        _hierarchyObject = hierarchyObject;
+        _universeObject = universeObject;
-        OnAssign(hierarchyObject);
+        OnAssign(universeObject);
-        OnHierarchyObjectAssigned?.Invoke(this);
+        OnUniverseObjectAssigned?.Invoke(this);
         return true;
     }
 
-    public bool Initialize()
+    protected override void InitializeInternal()
     {
-        if (IsInitialized)
+        Debug.Assert.AssertUniverseObjectAssigned(this);
-            return false;
-
-        NotAssignedException.Check(this, _hierarchyObject);
 
         foreach (IBehaviour behaviour in behaviours)
             behaviour.Initialize();
-
-        IsInitialized = true;
-        return true;
     }
 
-    public bool Finalize()
+    protected override void FinalizeInternal()
     {
-        if (!IsInitialized)
-            return false;
-
         foreach (IBehaviour behaviour in behaviours)
             behaviour.Finalize();
-
-        IsInitialized = false;
-        return true;
-    }
-
-    public bool Unassign()
-    {
-        if (IsInitialized)
-            return false;
-
-        _hierarchyObject = null!;
-        OnUnassigned?.Invoke(this);
-        return true;
-    }
-
-    public void Update()
-    {
-        if (!HierarchyObject.StateEnable.Enabled)
-            return;
-
-        OnPreUpdate?.Invoke(this);
-        OnUpdate?.Invoke(this);
-    }
-
-    public void UpdatePreDraw()
-    {
-        if (!HierarchyObject.StateEnable.Enabled)
-            return;
-
-        OnPreDraw?.Invoke(this);
     }
 
     public BehaviourController() { }
-    public BehaviourController(IHierarchyObject hierarchyObject) => Assign(hierarchyObject);
+    public BehaviourController(IUniverseObject universeObject) => Assign(universeObject);
 
     private void InsertBehaviourByPriority<T>(T behaviour) where T : class, IBehaviour
     {
@@ -209,12 +143,9 @@ public class BehaviourController : IBehaviourController
             behaviours.Add(behaviour);
     }
 
-    private void OnPriorityChange(IBehaviour sender, int previousPriority)
+    private void OnPriorityChange(IBehaviour sender, IBehaviour.PriorityChangedArguments args)
     {
         behaviours.Remove(sender);
         InsertBehaviourByPriority(sender);
     }
-
-    public IEnumerator<IBehaviour> GetEnumerator() => behaviours.GetEnumerator();
-    IEnumerator IEnumerable.GetEnumerator() => behaviours.GetEnumerator();
 }

Engine.Core/BehaviourInternal.cs

@@ -0,0 +1,56 @@
+namespace Engine.Core.Internal;
+
+[System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
+/// <summary>
+/// This behaviour can be used for core managers like <see cref="UpdateManager"/> etc. which need to be able to work even
+/// in a very bare minimum setup without the presence of <see cref="UniverseEntranceManager"/> to set themselves up on universe entrance.
+/// I recommend not using this unless you know what you are doing but it might come in handy for some use cases.
+/// </summary>
+public abstract class BehaviourIndependent : Behaviour
+{
+    private readonly Event<IUniverseObject, IUniverseObject.EnteredUniverseArguments>.EventHandler delegateEnteredUniverse = null!;
+    private readonly Event<IUniverseObject, IUniverseObject.ExitedUniverseArguments>.EventHandler delegateExitedUniverse = null!;
+
+    public BehaviourIndependent()
+    {
+        OnInitialized.AddListener(OnInitialize);
+        OnFinalized.AddListener(OnFinalize);
+        OnUnassigned.AddListener(OnUnassign);
+
+        delegateEnteredUniverse = EnteredUniverse;
+        delegateExitedUniverse = ExitedUniverse;
+    }
+
+    protected virtual void OnUnassign() { }
+    protected void OnUnassign(IAssignable assignable) => OnUnassign();
+
+    protected virtual void OnInitialize() { }
+    protected void OnInitialize(IInitializable _)
+    {
+        BehaviourController.UniverseObject.OnEnteredUniverse.AddListener(delegateEnteredUniverse);
+        BehaviourController.UniverseObject.OnExitedUniverse.AddListener(delegateExitedUniverse);
+
+        OnInitialize();
+
+        if (UniverseObject.IsInUniverse)
+            EnteredUniverse(UniverseObject, new(Universe));
+    }
+
+    protected virtual void OnFinalize() { }
+    protected void OnFinalize(IInitializable _)
+    {
+        BehaviourController.UniverseObject.OnEnteredUniverse.RemoveListener(delegateEnteredUniverse);
+        BehaviourController.UniverseObject.OnExitedUniverse.RemoveListener(delegateExitedUniverse);
+
+        OnFinalize();
+
+        if (UniverseObject.IsInUniverse)
+            ExitedUniverse(UniverseObject, new(Universe));
+    }
+
+    protected virtual void OnEnteredUniverse(IUniverse universe) { }
+    protected void EnteredUniverse(IUniverseObject sender, IUniverseObject.EnteredUniverseArguments args) => OnEnteredUniverse(args.Universe);
+
+    protected virtual void OnExitedUniverse(IUniverse universe) { }
+    protected void ExitedUniverse(IUniverseObject sender, IUniverseObject.ExitedUniverseArguments args) => OnExitedUniverse(args.Universe);
+}

Engine.Core/Collectors/ActiveBehaviourCollector.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace Engine.Core;
+
+public class ActiveBehaviourCollector<T> : ActiveBehaviourCollectorBase<T> where T : class, IBehaviour
+{
+    protected readonly FastList<T> activeBehaviours = new(32);
+    public override T this[Index index] => activeBehaviours[index];
+    public override int Count => activeBehaviours.Count;
+
+    public ActiveBehaviourCollector() { }
+    public ActiveBehaviourCollector(IUniverse universe) : base(universe) { }
+
+    protected override void AddBehaviour(T behaviour) => activeBehaviours.Add(behaviour);
+    protected override bool RemoveBehaviour(T tBehaviour) => activeBehaviours.Remove(tBehaviour);
+}

Engine.Core/Collectors/ActiveBehaviourCollectorBase.cs

@@ -0,0 +1,147 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public abstract class ActiveBehaviourCollectorBase<T> : IBehaviourCollector<T> where T : class, IBehaviour
+{
+    protected readonly Dictionary<IActive, T> monitoringActiveToBehaviour = new(32);
+    protected readonly FastList<T> monitoringBehaviours = new(32);
+
+    private readonly Event<IBehaviourController, IBehaviourController.BehaviourAddedArguments>.EventHandler delegateOnBehaviourAdded = null!;
+    private readonly Event<IBehaviourController, IBehaviourController.BehaviourRemovedArguments>.EventHandler delegateOnBehaviourRemoved = null!;
+    private readonly Event<IActive, IActive.ActiveChangedArguments>.EventHandler delegateOnBehaviourStateChanged = null!;
+    private readonly Event<IUniverse, IUniverse.UniverseObjectRegisteredArguments>.EventHandler delegateOnUniverseObjectRegistered = null!;
+    private readonly Event<IUniverse, IUniverse.UniverseObjectUnRegisteredArguments>.EventHandler delegateOnUniverseObjectUnregistered = null!;
+
+    public Event<IBehaviourCollector<T>, IBehaviourCollector<T>.BehaviourCollectedArguments> OnCollected { get; } = new();
+    public Event<IBehaviourCollector<T>, IBehaviourCollector<T>.BehaviourRemovedArguments> OnRemoved { get; } = new();
+    public Event<IHasUniverse> OnUniverseAssigned { get; } = new();
+    public Event<IAssignable>? OnUnassigned { get; } = new();
+
+    public abstract int Count { get; }
+
+    public abstract T this[Index index] { get; }
+    public IUniverse Universe { get; private set; } = null!;
+
+    public bool Assign(IUniverse universe)
+    {
+        if (Universe is not null)
+            return false;
+
+        foreach (IUniverseObject universeObject in universe)
+            OnUniverseObjectRegistered(universe, new(universeObject));
+
+        universe.OnUniverseObjectRegistered.AddListener(delegateOnUniverseObjectRegistered);
+        universe.OnUniverseObjectUnRegistered.AddListener(delegateOnUniverseObjectUnregistered);
+
+        Universe = universe;
+        OnUniverseAssigned?.Invoke(this);
+
+        return true;
+    }
+
+    public bool Unassign()
+    {
+        if (Universe is null)
+            return false;
+
+        foreach (IUniverseObject universeObject in Universe)
+            OnUniverseObjectUnregistered(Universe, new(universeObject));
+
+        Universe.OnUniverseObjectRegistered.RemoveListener(delegateOnUniverseObjectRegistered);
+        Universe.OnUniverseObjectUnRegistered.RemoveListener(delegateOnUniverseObjectUnregistered);
+
+        Universe = null!;
+        OnUnassigned?.Invoke(this);
+        return true;
+    }
+
+    protected abstract void AddBehaviour(T behaviour);
+    protected virtual void OnBehaviourAdd(IBehaviour behaviour) { }
+    private void OnBehaviourAdded(IBehaviourController controller, IBehaviourController.BehaviourAddedArguments args)
+    {
+        if (args.BehaviourAdded is not T tBehaviour)
+            return;
+
+        monitoringBehaviours.Add(tBehaviour);
+        monitoringActiveToBehaviour.Add(tBehaviour, tBehaviour);
+        tBehaviour.OnActiveChanged.AddListener(delegateOnBehaviourStateChanged);
+        OnBehaviourStateChanged(tBehaviour, new(!tBehaviour.IsActive));
+    }
+
+    protected abstract bool RemoveBehaviour(T behaviour);
+    protected virtual void OnBehaviourRemove(IBehaviour behaviour) { }
+    private void OnBehaviourRemoved(IBehaviourController controller, IBehaviourController.BehaviourRemovedArguments args)
+    {
+        if (args.BehaviourRemoved is not T tBehaviour)
+            return;
+
+        if (!monitoringBehaviours.Remove(tBehaviour) || !monitoringActiveToBehaviour.Remove(tBehaviour))
+            return;
+
+        tBehaviour.OnActiveChanged.RemoveListener(delegateOnBehaviourStateChanged);
+        if (!RemoveBehaviour(tBehaviour))
+            return;
+
+        OnBehaviourRemove(tBehaviour);
+        OnRemoved?.Invoke(this, new(tBehaviour));
+    }
+    private void OnBehaviourStateChanged(IActive sender, IActive.ActiveChangedArguments args)
+    {
+        T behaviour = monitoringActiveToBehaviour[sender];
+        if (sender.IsActive)
+        {
+            AddBehaviour(behaviour);
+            OnBehaviourAdd(behaviour);
+            OnCollected?.Invoke(this, new(behaviour));
+        }
+        else if (RemoveBehaviour(behaviour))
+        {
+            OnBehaviourRemove(behaviour);
+            OnRemoved?.Invoke(this, new(behaviour));
+        }
+    }
+
+    private void OnUniverseObjectRegistered(IUniverse manager, IUniverse.UniverseObjectRegisteredArguments args)
+    {
+        IUniverseObject universeObject = args.UniverseObjectRegistered;
+
+        universeObject.BehaviourController.OnBehaviourAdded.AddListener(delegateOnBehaviourAdded);
+        universeObject.BehaviourController.OnBehaviourRemoved.AddListener(delegateOnBehaviourRemoved);
+
+        for (int i = 0; i < universeObject.BehaviourController.Count; i++)
+            OnBehaviourAdded(universeObject.BehaviourController, new(universeObject.BehaviourController[i]));
+    }
+
+    private void OnUniverseObjectUnregistered(IUniverse manager, IUniverse.UniverseObjectUnRegisteredArguments args)
+    {
+        IUniverseObject universeObject = args.UniverseObjectUnregistered;
+
+        universeObject.BehaviourController.OnBehaviourAdded.RemoveListener(delegateOnBehaviourAdded);
+        universeObject.BehaviourController.OnBehaviourRemoved.RemoveListener(delegateOnBehaviourRemoved);
+
+        for (int i = 0; i < universeObject.BehaviourController.Count; i++)
+            OnBehaviourRemoved(universeObject.BehaviourController, new(universeObject.BehaviourController[i]));
+    }
+
+    public ActiveBehaviourCollectorBase()
+    {
+        delegateOnBehaviourAdded = OnBehaviourAdded;
+        delegateOnBehaviourRemoved = OnBehaviourRemoved;
+        delegateOnBehaviourStateChanged = OnBehaviourStateChanged;
+        delegateOnUniverseObjectRegistered = OnUniverseObjectRegistered;
+        delegateOnUniverseObjectUnregistered = OnUniverseObjectUnregistered;
+    }
+
+    public ActiveBehaviourCollectorBase(IUniverse universe)
+    {
+        delegateOnBehaviourAdded = OnBehaviourAdded;
+        delegateOnBehaviourRemoved = OnBehaviourRemoved;
+        delegateOnBehaviourStateChanged = OnBehaviourStateChanged;
+        delegateOnUniverseObjectRegistered = OnUniverseObjectRegistered;
+        delegateOnUniverseObjectUnregistered = OnUniverseObjectUnregistered;
+
+        Assign(universe);
+    }
+}

Engine.Core/Collectors/ActiveBehaviourCollectorOrdered.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public class ActiveBehaviourCollectorOrdered<TIndex, TItem> : ActiveBehaviourCollector<TItem> where TItem : class, IBehaviour where TIndex : IComparable
+{
+    private readonly SortedDictionary<TIndex, FastList<TItem>> behaviours = null!;
+    private readonly Dictionary<TItem, TIndex> indexCache = [];
+
+    private readonly Func<TItem, TIndex> getIndexFunc = null!;
+    private readonly IComparer<TIndex> sortBy = null!;
+
+    private int count = 0;
+    public override int Count => count;
+
+    public override TItem this[Index index]
+    {
+        get
+        {
+            int actualIndex = index.IsFromEnd
+                ? count - index.Value
+                : index.Value;
+
+            if (actualIndex < 0 || actualIndex >= count)
+                throw new IndexOutOfRangeException();
+
+            int leftIndex = actualIndex;
+            foreach ((TIndex i, FastList<TItem> list) in behaviours)
+            {
+                if (leftIndex < list.Count)
+                    return list[leftIndex];
+                leftIndex -= list.Count;
+            }
+            throw new IndexOutOfRangeException();
+        }
+    }
+
+    protected override bool RemoveBehaviour(TItem tBehaviour)
+    {
+        if (!indexCache.TryGetValue(tBehaviour, out TIndex? index) || !behaviours.TryGetValue(index, out FastList<TItem>? list))
+            throw new Exceptions.NotFoundException($"Index of '{index}' is not found in the collector");
+
+        if (!list.Remove(tBehaviour) || !indexCache.Remove(tBehaviour))
+            return false;
+
+        count--;
+        return true;
+    }
+
+    protected override void AddBehaviour(TItem behaviour)
+    {
+        TIndex key = getIndexFunc(behaviour);
+        if (!behaviours.TryGetValue(key, out FastList<TItem>? list))
+            behaviours[key] = list = [];
+
+        count++;
+        list.Add(behaviour);
+        indexCache.Add(behaviour, key);
+    }
+
+    public ActiveBehaviourCollectorOrdered(Func<TItem, TIndex> getIndexFunc, Comparison<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = Comparer<TIndex>.Create(sortBy);
+        behaviours = new(this.sortBy);
+    }
+
+    public ActiveBehaviourCollectorOrdered(IUniverse universe, Func<TItem, TIndex> getIndexFunc, Comparison<TIndex> sortBy) : base(universe)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = Comparer<TIndex>.Create(sortBy);
+        behaviours = new(this.sortBy);
+    }
+
+    public ActiveBehaviourCollectorOrdered(Func<TItem, TIndex> getIndexFunc, IComparer<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = sortBy;
+        behaviours = new(sortBy);
+    }
+
+    public ActiveBehaviourCollectorOrdered(IUniverse universe, Func<TItem, TIndex> getIndexFunc, IComparer<TIndex> sortBy) : base(universe)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = sortBy;
+        behaviours = new(sortBy);
+    }
+}

Engine.Core/Collectors/BehaviourCollector.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace Engine.Core;
+
+public class BehaviourCollector<T> : BehaviourCollectorBase<T> where T : class
+{
+    protected readonly FastList<T> behaviours = new(32);
+
+    public override T this[Index index] => behaviours[index];
+    public override int Count => behaviours.Count;
+
+    protected override void AddBehaviour(T behaviour) => behaviours.Add(behaviour);
+    protected override bool RemoveBehaviour(T tBehaviour) => behaviours.Remove(tBehaviour);
+
+    public BehaviourCollector() { }
+    public BehaviourCollector(IUniverse universe) : base(universe) { }
+}

Engine.Core/Collectors/BehaviourCollectorBase.cs

@@ -0,0 +1,124 @@
+using System;
+
+namespace Engine.Core;
+
+public abstract class BehaviourCollectorBase<T> : IBehaviourCollector<T> where T : class
+{
+    private readonly Event<IBehaviourController, IBehaviourController.BehaviourAddedArguments>.EventHandler delegateOnBehaviourAdded = null!;
+    private readonly Event<IBehaviourController, IBehaviourController.BehaviourRemovedArguments>.EventHandler delegateOnBehaviourRemoved = null!;
+    private readonly Event<IUniverse, IUniverse.UniverseObjectRegisteredArguments>.EventHandler delegateOnUniverseObjectRegistered = null!;
+    private readonly Event<IUniverse, IUniverse.UniverseObjectUnRegisteredArguments>.EventHandler delegateOnUniverseObjectUnregistered = null!;
+
+    public Event<IBehaviourCollector<T>, IBehaviourCollector<T>.BehaviourCollectedArguments> OnCollected { get; } = new();
+    public Event<IBehaviourCollector<T>, IBehaviourCollector<T>.BehaviourRemovedArguments> OnRemoved { get; } = new();
+    public Event<IHasUniverse> OnUniverseAssigned { get; } = new();
+    public Event<IAssignable>? OnUnassigned { get; } = new();
+
+    public IUniverse Universe { get; private set; } = null!;
+
+    public abstract int Count { get; }
+
+    public abstract T this[Index index] { get; }
+
+    public bool Assign(IUniverse universe)
+    {
+        if (Universe is not null)
+            return false;
+
+        foreach (IUniverseObject universeObject in universe)
+            OnUniverseObjectRegistered(universe, new(universeObject));
+
+        universe.OnUniverseObjectRegistered.AddListener(delegateOnUniverseObjectRegistered);
+        universe.OnPreUniverseObjectUnRegistered.AddListener(delegateOnUniverseObjectUnregistered);
+
+        Universe = universe;
+        OnAssign(universe);
+        OnUniverseAssigned?.Invoke(this);
+
+        return true;
+    }
+
+    public bool Unassign()
+    {
+        if (Universe is null)
+            return false;
+
+        foreach (IUniverseObject universeObject in Universe)
+            OnUniverseObjectUnregistered(Universe, new(universeObject));
+
+        Universe.OnUniverseObjectRegistered.RemoveListener(delegateOnUniverseObjectRegistered);
+        Universe.OnPreUniverseObjectUnRegistered.RemoveListener(delegateOnUniverseObjectUnregistered);
+
+        Universe = null!;
+        OnUnassigned?.Invoke(this);
+        return true;
+    }
+
+    protected virtual void OnAssign(IUniverse universe) { }
+
+    protected abstract void AddBehaviour(T behaviour);
+    protected virtual void OnBehaviourAdd(IBehaviour behaviour) { }
+    private void OnBehaviourAdded(IBehaviourController controller, IBehaviourController.BehaviourAddedArguments args)
+    {
+        if (args.BehaviourAdded is not T tBehaviour)
+            return;
+
+        AddBehaviour(tBehaviour);
+        OnBehaviourAdd(args.BehaviourAdded);
+        OnCollected?.Invoke(this, new(tBehaviour));
+    }
+
+    protected abstract bool RemoveBehaviour(T tBehaviour);
+    protected virtual void OnBehaviourRemove(IBehaviour behaviour) { }
+    private void OnBehaviourRemoved(IBehaviourController controller, IBehaviourController.BehaviourRemovedArguments args)
+    {
+        if (args.BehaviourRemoved is not T tBehaviour)
+            return;
+
+        if (!RemoveBehaviour(tBehaviour))
+            return;
+
+        OnBehaviourRemove(args.BehaviourRemoved);
+        OnRemoved?.Invoke(this, new(tBehaviour));
+    }
+
+    private void OnUniverseObjectRegistered(IUniverse manager, IUniverse.UniverseObjectRegisteredArguments args)
+    {
+        IUniverseObject universeObject = args.UniverseObjectRegistered;
+
+        universeObject.BehaviourController.OnBehaviourAdded.AddListener(delegateOnBehaviourAdded);
+        universeObject.BehaviourController.OnBehaviourRemoved.AddListener(delegateOnBehaviourRemoved);
+
+        for (int i = 0; i < universeObject.BehaviourController.Count; i++)
+            OnBehaviourAdded(universeObject.BehaviourController, new(universeObject.BehaviourController[i]));
+    }
+
+    private void OnUniverseObjectUnregistered(IUniverse manager, IUniverse.UniverseObjectUnRegisteredArguments args)
+    {
+        IUniverseObject universeObject = args.UniverseObjectUnregistered;
+
+        universeObject.BehaviourController.OnBehaviourAdded.RemoveListener(delegateOnBehaviourAdded);
+        universeObject.BehaviourController.OnBehaviourRemoved.RemoveListener(delegateOnBehaviourRemoved);
+
+        for (int i = 0; i < universeObject.BehaviourController.Count; i++)
+            OnBehaviourRemoved(universeObject.BehaviourController, new(universeObject.BehaviourController[i]));
+    }
+
+    public BehaviourCollectorBase()
+    {
+        delegateOnBehaviourAdded = OnBehaviourAdded;
+        delegateOnBehaviourRemoved = OnBehaviourRemoved;
+        delegateOnUniverseObjectRegistered = OnUniverseObjectRegistered;
+        delegateOnUniverseObjectUnregistered = OnUniverseObjectUnregistered;
+    }
+
+    public BehaviourCollectorBase(IUniverse universe)
+    {
+        delegateOnBehaviourAdded = OnBehaviourAdded;
+        delegateOnBehaviourRemoved = OnBehaviourRemoved;
+        delegateOnUniverseObjectRegistered = OnUniverseObjectRegistered;
+        delegateOnUniverseObjectUnregistered = OnUniverseObjectUnregistered;
+
+        Assign(universe);
+    }
+}

Engine.Core/Collectors/BehaviourCollectorOrdered.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public class BehaviourCollectorOrdered<TIndex, TItem> : BehaviourCollectorBase<TItem> where TItem : class where TIndex : IComparable
+{
+    private readonly SortedDictionary<TIndex, FastList<TItem>> behaviours = null!;
+    private readonly Dictionary<TItem, TIndex> indexCache = null!;
+
+    private readonly Func<TItem, TIndex> getIndexFunc = null!;
+    private readonly IComparer<TIndex> sortBy = null!;
+
+    private int count = 0;
+    public override int Count => count;
+
+    public override TItem this[Index index]
+    {
+        get
+        {
+            int actualIndex = index.IsFromEnd
+                ? count - index.Value
+                : index.Value;
+
+            if (actualIndex < 0 || actualIndex >= count)
+                throw new IndexOutOfRangeException();
+
+            int leftIndex = actualIndex;
+            foreach ((TIndex i, FastList<TItem> list) in behaviours)
+            {
+                if (leftIndex < list.Count)
+                    return list[leftIndex];
+                leftIndex -= list.Count;
+            }
+            throw new IndexOutOfRangeException();
+        }
+    }
+
+    protected override bool RemoveBehaviour(TItem tBehaviour)
+    {
+        if (!indexCache.TryGetValue(tBehaviour, out TIndex? index) || !behaviours.TryGetValue(index, out FastList<TItem>? list))
+            throw new Exceptions.NotFoundException($"Index of '{index}' is not found in the collector");
+
+        if (!list.Remove(tBehaviour) || !indexCache.Remove(tBehaviour))
+            return false;
+
+        count--;
+        return true;
+    }
+
+    protected override void AddBehaviour(TItem behaviour)
+    {
+        TIndex key = getIndexFunc(behaviour);
+        if (!behaviours.TryGetValue(key, out FastList<TItem>? list))
+            behaviours[key] = list = [];
+
+        count++;
+        list.Add(behaviour);
+        indexCache.Add(behaviour, key);
+    }
+
+    public BehaviourCollectorOrdered(Func<TItem, TIndex> getIndexFunc, Comparison<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = Comparer<TIndex>.Create(sortBy);
+        behaviours = new(this.sortBy);
+    }
+
+    public BehaviourCollectorOrdered(IUniverse universe, Func<TItem, TIndex> getIndexFunc, Comparison<TIndex> sortBy) : base(universe)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = Comparer<TIndex>.Create(sortBy);
+        behaviours = new(this.sortBy);
+    }
+
+    public BehaviourCollectorOrdered(Func<TItem, TIndex> getIndexFunc, IComparer<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = sortBy;
+        behaviours = new(sortBy);
+    }
+
+    public BehaviourCollectorOrdered(IUniverse universe, Func<TItem, TIndex> getIndexFunc, IComparer<TIndex> sortBy) : base(universe)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = sortBy;
+        behaviours = new(sortBy);
+    }
+}

Engine.Core/Debug/AssertHelpers.cs

@@ -0,0 +1,46 @@
+using System.Runtime.CompilerServices;
+
+namespace Engine.Core.Debug;
+
+public static class Assert
+{
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertTrue(bool value, string errorMessage)
+        => System.Diagnostics.Debug.Assert(value, errorMessage);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertFalse(bool value, string errorMessage)
+        => System.Diagnostics.Debug.Assert(!value, errorMessage);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertNull(object? value, string errorMessage)
+        => System.Diagnostics.Debug.Assert(value is null, errorMessage);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertNotNull(object? value, string errorMessage)
+        => System.Diagnostics.Debug.Assert(value is not null, errorMessage);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertInitialized(IInitializable initializable)
+        => System.Diagnostics.Debug.Assert(initializable.IsInitialized, $"{initializable.GetType().Name} must be initialized");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertBehaviourControllerAssigned(IHasBehaviourController assignable)
+        => System.Diagnostics.Debug.Assert(assignable.BehaviourController is not null, $"{assignable.GetType().Name} must be assigned an {nameof(IBehaviourController)}");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertEntityAssigned(IHasEntity assignable)
+        => System.Diagnostics.Debug.Assert(assignable.Entity is not null, $"{assignable.GetType().Name} must be assigned an {nameof(IEntity)}");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertUniverseAssigned(IHasUniverse assignable)
+        => System.Diagnostics.Debug.Assert(assignable.Universe is not null, $"{assignable.GetType().Name} must be assigned an {nameof(IUniverse)}");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertUniverseObjectAssigned(IHasUniverseObject assignable)
+        => System.Diagnostics.Debug.Assert(assignable.UniverseObject is not null, $"{assignable.GetType().Name} must be assigned an {nameof(IUniverseObject)}");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void AssertStateEnableAssigned(IHasStateEnable assignable)
+        => System.Diagnostics.Debug.Assert(assignable.StateEnable is not null, $"{assignable.GetType().Name} must be assigned an {nameof(IStateEnable)}");
+}

Engine.Core/Debug/ConsoleLogger.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace Engine.Core.Debug;
+
+public class ConsoleLogger : LoggerBase
+{
+    protected override void Write(string message) => Console.WriteLine(message);
+}

Engine.Core/Debug/FileLogger.cs

@@ -0,0 +1,32 @@
+using System;
+using System.IO;
+
+namespace Engine.Core.Debug;
+
+public class FileLogger : LoggerBase
+{
+    public readonly string FilePath;
+
+    protected override void Write(string message)
+    {
+        File.AppendAllTextAsync(FilePath, $"{message}{Environment.NewLine}");
+    }
+
+    public FileLogger(string filePath)
+    {
+        if (!filePath.EndsWith(".log"))
+            filePath += ".log";
+
+        FilePath = filePath;
+
+        bool isRelativePath = Path.GetFullPath(filePath).CompareTo(filePath) != 0;
+
+        if (isRelativePath)
+            FilePath = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, filePath));
+
+        if (Path.GetDirectoryName(FilePath) is string directoryPath)
+            Directory.CreateDirectory(directoryPath);
+
+        File.Open(FilePath, FileMode.Create).Close();
+    }
+}

Engine.Core/Debug/ILogger.cs

@@ -0,0 +1,18 @@
+namespace Engine.Core.Debug;
+
+public interface ILogger
+{
+    static ILogger Shared { get; set; } = new ConsoleLogger();
+
+    Level FilterLevel { get; set; }
+
+    void Log(string message, Level level = Level.Info, bool force = false);
+
+    enum Level
+    {
+        Trace,
+        Info,
+        Warning,
+        Error,
+    };
+}

Engine.Core/Debug/LoggerBase.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace Engine.Core.Debug;
+
+public abstract class LoggerBase : ILogger
+{
+    public ILogger.Level FilterLevel { get; set; } = ILogger.Level.Trace;
+
+    public void Log(string message, ILogger.Level level = ILogger.Level.Info, bool force = false)
+    {
+        if (!force && level < FilterLevel)
+            return;
+
+        string timestamp = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss tt");
+
+        Write($"[{timestamp}] [{level}] \t{message}");
+    }
+
+    protected abstract void Write(string message);
+}

Engine.Core/Debug/LoggerContainer.cs

@@ -0,0 +1,9 @@
+namespace Engine.Core.Debug;
+
+public class LoggerContainer : Behaviour, ILogger
+{
+    public ILogger Logger { get; set; } = ILogger.Shared;
+
+    public ILogger.Level FilterLevel { get => Logger.FilterLevel; set => Logger.FilterLevel = value; }
+    public void Log(string message, ILogger.Level level = ILogger.Level.Info, bool force = false) => Logger.Log(message, level, force);
+}

Engine.Core/Debug/LoggerExtensions.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Diagnostics;
+
+namespace Engine.Core.Debug;
+
+public static class LoggerExtensions
+{
+    public static void Log<T>(this ILogger logger, T caller, string message, ILogger.Level level = ILogger.Level.Info, bool force = false)
+    {
+        string body = $"{caller?.GetType().Name ?? typeof(T).Name}: {message}";
+        logger.Log(body, level, force);
+    }
+
+    public static void LogWarning<T>(this ILogger logger, T caller, string message, bool force = false) => Log(logger, caller, message, ILogger.Level.Info, force);
+
+    public static void LogError<T>(this ILogger logger, T caller, string message, bool force = false)
+    {
+        Log(logger, caller, message, ILogger.Level.Error, force);
+        LogTrace(logger, caller, new StackTrace(), force);
+    }
+
+    public static void LogException<T>(this ILogger logger, T caller, Exception exception, bool force = false)
+    {
+        Log(logger, caller, $"Exception of type {exception.GetType().Name} occured", ILogger.Level.Error, force);
+        Log(logger, caller, $"Message: {exception.Message}", ILogger.Level.Error, force);
+        Log(logger, caller, $"InnerException: {exception.InnerException}", ILogger.Level.Error, force);
+
+        // Not using LogTrace because exception.StackTrace is a type of string
+        Log(logger, caller, $"{nameof(StackTrace)}:{Environment.NewLine}{exception.StackTrace}", ILogger.Level.Trace);
+    }
+
+    public static void LogTrace<T>(this ILogger logger, T caller, StackTrace? stackTrace = null, bool force = false)
+    {
+        Log(logger, caller, $"{nameof(StackTrace)}:{Environment.NewLine}{stackTrace ?? new()}", ILogger.Level.Trace, force);
+    }
+}

Engine.Core/Debug/LoggerWrapper.cs

@@ -0,0 +1,23 @@
+namespace Engine.Core.Debug;
+
+public class LoggerWrapper(ILogger firstLogger, ILogger secondLogger) : ILogger
+{
+    private readonly ILogger firstLogger = firstLogger;
+    private readonly ILogger secondLogger = secondLogger;
+
+    public ILogger.Level FilterLevel
+    {
+        get => firstLogger.FilterLevel;
+        set
+        {
+            firstLogger.FilterLevel = value;
+            secondLogger.FilterLevel = value;
+        }
+    }
+
+    public void Log(string message, ILogger.Level level = ILogger.Level.Info, bool force = false)
+    {
+        firstLogger.Log(message, level, force);
+        secondLogger.Log(message, level, force);
+    }
+}

Engine.Core/Debug/LoggerWrapperExtensions.cs

@@ -0,0 +1,6 @@
+namespace Engine.Core.Debug;
+
+public static class LoggerWrapperExtensions
+{
+    public static ILogger WrapWith(this ILogger thisLogger, ILogger logger) => new LoggerWrapper(thisLogger, logger);
+}

Engine.Core/Debug/RotatingFileLogger.cs

@@ -0,0 +1,71 @@
+using System;
+using System.IO;
+using System.Linq;
+
+namespace Engine.Core.Debug;
+
+public class RotatingFileLogger : ILogger
+{
+    public readonly FileLogger FileLogger = null!;
+    public readonly string Directory = string.Empty;
+    public readonly int RotateLength = 3;
+
+    public RotatingFileLogger(string directory, string namePrefix, string nameSuffix = "", int rotateLength = 3)
+    {
+        RotateLength = rotateLength;
+
+        string fileName = Path.Combine(directory, namePrefix);
+        if (!string.IsNullOrWhiteSpace(nameSuffix))
+            fileName += $"_{nameSuffix}";
+
+        bool isRelativePath = Path.GetFullPath(fileName).CompareTo(fileName) != 0;
+
+        if (isRelativePath)
+            fileName = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, fileName));
+
+        if (File.Exists($"{fileName}.log"))
+            RenameExistingLogs(fileName, RotateLength);
+
+        FileLogger = new(fileName);
+
+        Directory = Path.GetDirectoryName(fileName) ?? throw new("Unexpected error on getting directory of logger path");
+        RotateLastLogs(Directory, namePrefix, RotateLength);
+    }
+
+    private static void RenameExistingLogs(string filePath, int rotateLength)
+    {
+        for (int i = rotateLength - 1; i >= 0; i--)
+        {
+            string source = i == 0
+                ? $"{filePath}.log"
+                : $"{filePath}_{i}.log";
+
+            string dest = $"{filePath}_{i + 1}.log";
+
+            if (!File.Exists(source))
+                continue;
+
+            if (File.Exists(dest))
+                File.Delete(dest);
+
+            File.Move(source, dest);
+        }
+    }
+
+    private static void RotateLastLogs(string directory, string prefix, int rotateLength)
+    {
+        IOrderedEnumerable<string> logs = System.IO.Directory.GetFiles(directory, $"{prefix}*.log")
+            .OrderBy(File.GetCreationTime);
+
+        foreach (string file in logs.Skip(rotateLength))
+            try
+            {
+                ILogger.Shared.Log($"Removing log file located at \"{file}\" during rotation.");
+                File.Delete(file);
+            }
+            catch (Exception e) { ILogger.Shared.LogException($"Failed to rotate log file at \"{file}\"", e); }
+    }
+
+    public ILogger.Level FilterLevel { get => FileLogger.FilterLevel; set => FileLogger.FilterLevel = value; }
+    public void Log(string message, ILogger.Level level = ILogger.Level.Info, bool force = false) => FileLogger.Log(message, level, force);
+}

Engine.Core/Engine.Core.csproj

@@ -1,10 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
     <ImplicitUsings>false</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <RootNamespace>Syntriax.Engine.Core</RootNamespace>
+    <RootNamespace>Engine.Core</RootNamespace>
+    <AssemblyName>Engine.Core</AssemblyName>
   </PropertyGroup>
 
 </Project>

Engine.Core/Engine.Core.puml

@@ -6,41 +6,41 @@ skinparam nodesep 100
 
 title Core Engine Relations
 
-interface Engine.Core.Abstract.IEntity extends Engine.Core.Abstract.IInitializable {}
+interface Engine.Core.IEntity extends Engine.Core.IInitializable {}
-interface Engine.Core.Abstract.IHierarchyObject extends Engine.Core.Abstract.IEntity, Engine.Core.Abstract.INameable {}
+interface Engine.Core.IUniverseObject extends Engine.Core.IEntity, Engine.Core.INameable {}
 
-interface Engine.Core.Abstract.INameable {}
+interface Engine.Core.INameable {}
 
-Engine.Core.Abstract.IHierarchyObject --> Engine.Core.Abstract.IBehaviourController: has
+Engine.Core.IUniverseObject --> Engine.Core.IBehaviourController: has
-Engine.Core.Abstract.IBehaviourController "1" --> "0..*" Engine.Core.Abstract.IBehaviour: has
+Engine.Core.IBehaviourController "1" --> "0..*" Engine.Core.IBehaviour: has
 
-interface Engine.Core.Abstract.IBehaviourController {}
+interface Engine.Core.IBehaviourController {}
-interface Engine.Core.Abstract.IBehaviour {}
+interface Engine.Core.IBehaviour {}
-interface Engine.Core.Abstract.IBehaviour2D extends Engine.Core.Abstract.IBehaviour {}
+interface Engine.Core.IBehaviour2D extends Engine.Core.IBehaviour {}
-interface Engine.Core.Abstract.IBehaviour3D extends Engine.Core.Abstract.IBehaviour {}
+interface Engine.Core.IBehaviour3D extends Engine.Core.IBehaviour {}
 
-interface Engine.Core.Abstract.IGameManager {}
+interface Engine.Core.IUniverse {}
-Engine.Core.Abstract.IGameManager "1" -r-> "0..*" Engine.Core.Abstract.IHierarchyObject: has
+Engine.Core.IUniverse "1" -r-> "0..*" Engine.Core.IUniverseObject: has
 
 ' together {
-'     interface Engine.Core.Abstract.IAssignable {}
+'     interface Engine.Core.IAssignable {}
-'     interface Engine.Core.Abstract.IHasStateEnable extends Engine.Core.Abstract.IAssignable {}
+'     interface Engine.Core.IHasStateEnable extends Engine.Core.IAssignable {}
-'     interface Engine.Core.Abstract.IHasGameManager extends Engine.Core.Abstract.IAssignable {}
+'     interface Engine.Core.IHasUniverse extends Engine.Core.IAssignable {}
-'     interface Engine.Core.Abstract.IHasHierarchyObject extends Engine.Core.Abstract.IAssignable {}
+'     interface Engine.Core.IHasUniverseObject extends Engine.Core.IAssignable {}
-'     interface Engine.Core.Abstract.IHasBehaviourController extends Engine.Core.Abstract.IAssignable {}
+'     interface Engine.Core.IHasBehaviourController extends Engine.Core.IAssignable {}
-'     ' Engine.Core.Abstract.IHasStateEnable --> Engine.Core.Abstract.IStateEnable: has
+'     ' Engine.Core.IHasStateEnable --> Engine.Core.IStateEnable: has
-'     ' Engine.Core.Abstract.IHasGameManager --> Engine.Core.Abstract.IGameManager: has
+'     ' Engine.Core.IHasUniverse --> Engine.Core.IUniverse: has
-'     ' Engine.Core.Abstract.IHasHierarchyObject --> Engine.Core.Abstract.IHierarchyObject: has
+'     ' Engine.Core.IHasUniverseObject --> Engine.Core.IUniverseObject: has
-'     ' Engine.Core.Abstract.IHasBehaviourController --> Engine.Core.Abstract.IBehaviourController: has
+'     ' Engine.Core.IHasBehaviourController --> Engine.Core.IBehaviourController: has
 ' }
 
 together {
-    interface Engine.Core.Abstract.ITransform2D {}
+    interface Engine.Core.ITransform2D {}
-    interface Engine.Core.Abstract.ICamera2D {}
+    interface Engine.Core.ICamera2D {}
-    interface Engine.Core.Abstract.ICoroutineYield {}
+    interface Engine.Core.ICoroutineYield {}
-    interface Engine.Core.Abstract.IStateEnable {}
+    interface Engine.Core.IStateEnable {}
-    interface Engine.Core.Abstract.IInitializable {}
+    interface Engine.Core.IInitializable {}
-    interface Engine.Core.Abstract.IBehaviourCollector {}
+    interface Engine.Core.IBehaviourCollector {}
 }
 
 @enduml

Engine.Core/Exceptions/AssignException.cs

@@ -1,12 +0,0 @@
-using System;
-
-namespace Syntriax.Engine.Core.Exceptions;
-
-public class AssignException : Exception
-{
-    public AssignException() : base("Assign operation has failed.") { }
-    public AssignException(string? message) : base(message) { }
-
-    public static AssignException From<T, T2>(T to, T2? value)
-        => new($"Assign operation has failed on T: {to?.GetType().FullName ?? "\"null\""}, value: {value?.GetType().ToString() ?? "\"null\""}");
-}

Engine.Core/Exceptions/AssignFailedException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Engine.Core.Exceptions;
+
+public class AssignFailedException(string? message) : Exception(message)
+{
+    public static AssignFailedException From<T, T2>(T to, T2? value)
+        => new($"Assign operation has failed on T: {to?.GetType().FullName ?? "\"null\""}, value: {value?.GetType().ToString() ?? "\"null\""}");
+}

Engine.Core/Exceptions/BehaviourNotFoundException.cs

@@ -0,0 +1,3 @@
+namespace Engine.Core.Exceptions;
+
+public class BehaviourNotFoundException(string? message) : NotFoundException(message);

Engine.Core/Exceptions/NotAssignedException.cs

@@ -1,21 +1,9 @@
 using System;
-using Syntriax.Engine.Core.Abstract;
 
-namespace Syntriax.Engine.Core.Exceptions;
+namespace Engine.Core.Exceptions;
 
-public class NotAssignedException : Exception
+public class NotAssignedException(string? message) : Exception(message)
 {
-    public NotAssignedException() : base("The object has not been assigned.") { }
-    public NotAssignedException(string? message) : base(message) { }
-
     public static NotAssignedException From<T1, T2>(T1 to, T2? value)
         => new($"{value?.GetType().FullName ?? "\"null\""} has not been assigned to {to?.GetType().FullName ?? "\"null\""}");
-
-    public static void Check<T1, T2>(T1 to, T2? value)
-    {
-        if (value is not null)
-            return;
-
-        throw From(to, value);
-    }
 }

Engine.Core/Exceptions/NotFoundException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Engine.Core.Exceptions;
+
+public class NotFoundException(string? message) : Exception(message)
+{
+    public static NotAssignedException FromType<T>()
+        => new($"{typeof(T).FullName} was not found");
+}

Engine.Core/Exceptions/UniverseObjectNotFoundException.cs

@@ -0,0 +1,3 @@
+namespace Engine.Core.Exceptions;
+
+public class UniverseObjectNotFoundException(string? message) : NotFoundException(message);

Engine.Core/Extensions/BehaviourControllerExtensions.cs

@@ -1,8 +1,9 @@
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 
-using Syntriax.Engine.Core.Abstract;
+using Engine.Core.Exceptions;
 
-namespace Syntriax.Engine.Core;
+namespace Engine.Core;
 
 public static class BehaviourControllerExtensions
 {
@@ -19,6 +20,15 @@ public static class BehaviourControllerExtensions
         return behaviour is not null;
     }
 
+    /// <summary>
+    /// Gets a <see cref="IBehaviour"/> of the specified type in the provided <see cref="IBehaviourController"/>. Throws an error if not found.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
+    /// <returns>The <see cref="IBehaviour"/> of the specified type if found; otherwise, throws <see cref="BehaviourNotFoundException"/>.</returns>
+    public static T GetRequiredBehaviour<T>(this IBehaviourController behaviourController) where T : class
+        => behaviourController.GetBehaviour<T>() ?? throw new BehaviourNotFoundException($"{behaviourController.UniverseObject?.Name ?? "NULL"}'s {nameof(IBehaviourController)} does not contain any {typeof(T).FullName}");
+
     /// <summary>
     /// Gets an existing <see cref="IBehaviour"/> of the specified type, or adds and returns a new one if it doesn't exist.
     /// </summary>
@@ -30,12 +40,25 @@ public static class BehaviourControllerExtensions
         => behaviourController.GetBehaviour<T>() ?? behaviourController.AddBehaviour<T>(args);
 
     /// <summary>
-    /// Tries to get a <see cref="IBehaviour"/> of the specified type in the parent hierarchy.
+    /// Gets an existing <see cref="IBehaviour"/> of the specified type, or adds and returns the fallback type if it doesn't exist.
+    /// </summary>
+    /// <typeparam name="TOriginal">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <typeparam name="TFallback">The type of <see cref="IBehaviour"/> to add. It must be assignable from <typeparamref name="TOriginal"/></typeparam>
+    /// <param name="behaviourController">The <see cref="IBehaviourController"/> to search in.</param>
+    /// <param name="args">Optional arguments to pass to the constructor of the <see cref="IBehaviour"/> if a new one is added.</param>
+    /// <returns>The existing or newly added <see cref="IBehaviour"/> of the specified type.</returns>
+    public static TOriginal GetOrAddBehaviour<TOriginal, TFallback>(this IBehaviourController behaviourController, params object?[]? args)
+            where TOriginal : class
+            where TFallback : class, IBehaviour, TOriginal
+        => behaviourController.GetBehaviour<TOriginal>() ?? behaviourController.AddBehaviour<TFallback>(args);
+
+    /// <summary>
+    /// Tries to get a <see cref="IBehaviour"/> of the specified type in it's <see cref="IUniverseObject"/>'s parents recursively.
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
     /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
     /// <param name="behaviour">When this method returns, contains the <see cref="IBehaviour"/> of the specified type, if found; otherwise, null.</param>
-    /// <returns><see cref="true"/> if a <see cref="IBehaviour"/> of the specified type was found in the parent hierarchy; otherwise, <see cref="false"/>.</returns>
+    /// <returns><see cref="true"/> if a <see cref="IBehaviour"/> of the specified type was found in the parent universe; otherwise, <see cref="false"/>.</returns>
     public static bool TryGetBehaviourInParent<T>(this IBehaviourController behaviourController, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
     {
         behaviour = GetBehaviourInParent<T>(behaviourController);
@@ -43,7 +66,7 @@ public static class BehaviourControllerExtensions
     }
 
     /// <summary>
-    /// Gets a <see cref="IBehaviour"/> of the specified type in the parent hierarchy.
+    /// Gets a <see cref="IBehaviour"/> of the specified type in it's <see cref="IUniverseObject"/>'s parents recursively.
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
     /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
@@ -57,19 +80,47 @@ public static class BehaviourControllerExtensions
             if (controller.GetBehaviour<T>() is T behaviour)
                 return behaviour;
 
-            controller = controller.HierarchyObject.Parent?.BehaviourController;
+            controller = controller.UniverseObject.Parent?.BehaviourController;
         }
 
         return default;
     }
 
     /// <summary>
-    /// Tries to get a <see cref="IBehaviour"/> of the specified type in the child hierarchy.
+    /// Gets a <see cref="IBehaviour"/> of the specified type in it's <see cref="IUniverseObject"/>'s parents recursively. Throws an error if not found.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
+    /// <returns>The <see cref="IBehaviour"/> of the specified type if found; otherwise, throws <see cref="BehaviourNotFoundException"/>.</returns>
+    public static T GetRequiredBehaviourInParent<T>(this IBehaviourController behaviourController) where T : class
+        => behaviourController.GetBehaviourInParent<T>() ?? throw new BehaviourNotFoundException($"{behaviourController.UniverseObject?.Name ?? "NULL"}'s {nameof(IBehaviourController)} does not contain any {typeof(T).FullName} on any parent");
+
+    /// <summary>
+    /// Gets all <see cref="IBehaviour"/>s of the specified type in it's <see cref="IUniverseObject"/>'s parents recursively and stores them in the provided list.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
+    /// <param name="behavioursInParent">The list to store the <see cref="IBehaviour"/>s.</param>
+    /// <param name="collectionMethod">Whether to clear the <paramref name="behavioursInParent"/> before collection or append the results to the list.</param>
+    public static void GetBehavioursInParent<T>(this IBehaviourController behaviourController, IList<T> behavioursInParent, IBehaviourController.CollectionMethod collectionMethod = IBehaviourController.CollectionMethod.Clear) where T : class
+    {
+        if (collectionMethod == IBehaviourController.CollectionMethod.Clear)
+            behavioursInParent.Clear();
+
+        IBehaviourController? controller = behaviourController;
+        while (controller is not null)
+        {
+            controller.GetBehaviours(behavioursInParent, IBehaviourController.CollectionMethod.Append);
+            controller = controller.UniverseObject.Parent?.BehaviourController;
+        }
+    }
+
+    /// <summary>
+    /// Tries to get a <see cref="IBehaviour"/> of the specified type in it's <see cref="IUniverseObject"/>'s children recursively.
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
     /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
     /// <param name="behaviour">When this method returns, contains the <see cref="IBehaviour"/> of the specified type, if found; otherwise, null.</param>
-    /// <returns><see cref="true"/> if a <see cref="IBehaviour"/> of the specified type was found in the child hierarchy; otherwise, <see cref="false"/>.</returns>
+    /// <returns><see cref="true"/> if a <see cref="IBehaviour"/> of the specified type was found in the child universe; otherwise, <see cref="false"/>.</returns>
     public static bool TryGetBehaviourInChildren<T>(this IBehaviourController behaviourController, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
     {
         behaviour = GetBehaviourInChildren<T>(behaviourController);
@@ -77,7 +128,7 @@ public static class BehaviourControllerExtensions
     }
 
     /// <summary>
-    /// Gets a <see cref="IBehaviour"/> of the specified type in the child hierarchy.
+    /// Gets a <see cref="IBehaviour"/> of the specified type in it's <see cref="IUniverseObject"/>'s children recursively.
     /// </summary>
     /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
     /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
@@ -87,10 +138,41 @@ public static class BehaviourControllerExtensions
         if (behaviourController.GetBehaviour<T>() is T localBehaviour)
             return localBehaviour;
 
-        foreach (IHierarchyObject child in behaviourController.HierarchyObject)
+        foreach (IUniverseObject child in behaviourController.UniverseObject.Children)
             if (GetBehaviourInChildren<T>(child.BehaviourController) is T behaviour)
                 return behaviour;
 
         return default;
     }
+
+    /// <summary>
+    /// Gets a <see cref="IBehaviour"/> of the specified type in the children recursively. Throws an error if not found.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <param name="behaviourController">The <see cref="IBehaviourController"/> to start searching from.</param>
+    /// <returns>The <see cref="IBehaviour"/> of the specified type if found; otherwise, throws <see cref="BehaviourNotFoundException"/>.</returns>
+    public static T GetRequiredBehaviourInChildren<T>(this IBehaviourController behaviourController) where T : class
+        => behaviourController.GetBehaviourInChildren<T>() ?? throw new BehaviourNotFoundException($"{behaviourController.UniverseObject?.Name ?? "NULL"}'s {nameof(IBehaviourController)} does not contain any {typeof(T).FullName} on any children ");
+
+    /// <summary>
+    /// Gets all <see cref="IBehaviour"/>s of the specified type in it's <see cref="IUniverseObject"/>'s children recursively and stores them in the provided list.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/>s to get.</typeparam>
+    /// <param name="behavioursInChildren">The list to store the <see cref="IBehaviour"/>s.</param>
+    /// <param name="collectionMethod">Whether to clear the <paramref name="behavioursInChildren"/> before collection or append the results to the list.</param>
+    public static void GetBehavioursInChildren<T>(this IBehaviourController behaviourController, IList<T> behavioursInChildren, IBehaviourController.CollectionMethod collectionMethod = IBehaviourController.CollectionMethod.Clear) where T : class
+    {
+        if (collectionMethod == IBehaviourController.CollectionMethod.Clear)
+            behavioursInChildren.Clear();
+
+        TraverseChildrenForBehaviour(behaviourController.UniverseObject, behavioursInChildren);
+    }
+
+    private static void TraverseChildrenForBehaviour<T>(IUniverseObject universeObject, IList<T> behaviours) where T : class
+    {
+        universeObject.BehaviourController.GetBehaviours(behaviours, IBehaviourController.CollectionMethod.Append);
+
+        foreach (IUniverseObject child in universeObject.Children)
+            TraverseChildrenForBehaviour(child, behaviours);
+    }
 }

Engine.Core/Extensions/BehaviourExtensions.cs

@@ -1,36 +0,0 @@
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public static class BehaviourExtensions
-{
-    public static T? FindBehaviour<T>(this IEnumerable<IHierarchyObject> hierarchyObjects) where T : class
-    {
-        foreach (IHierarchyObject hierarchyObject in hierarchyObjects)
-            if (hierarchyObject.BehaviourController.GetBehaviour<T>() is T behaviour)
-                return behaviour;
-
-        return default;
-    }
-
-    public static bool TryFindBehaviour<T>(this IEnumerable<IHierarchyObject> hierarchyObjects, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
-    {
-        behaviour = FindBehaviour<T>(hierarchyObjects);
-        return behaviour is not null;
-    }
-
-    public static void FindBehaviours<T>(this IEnumerable<IHierarchyObject> hierarchyObjects, List<T> behaviours) where T : class
-    {
-        behaviours.Clear();
-        List<T> cache = [];
-
-        foreach (IHierarchyObject hierarchyObject in hierarchyObjects)
-        {
-            hierarchyObject.BehaviourController.GetBehaviours(cache);
-            behaviours.AddRange(cache);
-        }
-    }
-}

Engine.Core/Extensions/EnumExtensions.cs

@@ -1,6 +1,6 @@
 using System;
 
-namespace Syntriax.Engine.Core;
+namespace Engine.Core;
 
 public static class EnumExtensions
 {

Engine.Core/Extensions/FloatExtensions.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core;
+namespace Engine.Core;
 
 public static class FloatExtensions
 {

Engine.Core/Extensions/GameManagerExtensions.cs

@@ -1,9 +0,0 @@
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public static class GameManagerExtensions
-{
-    public static IHierarchyObject InstantiateHierarchyObject(this IGameManager gameManager, params object?[]? args)
-        => gameManager.InstantiateHierarchyObject<HierarchyObject>(args);
-}

Engine.Core/Extensions/HierarchyObjectExtensions.cs

@@ -1,41 +0,0 @@
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-public static class HierarchyObjectExtensions
-{
-    public static T SetHierarchyObject<T>(this T hierarchyObject, string? name = "", IHierarchyObject? parent = null) where T : IHierarchyObject
-    {
-        if (!string.IsNullOrWhiteSpace(name))
-            hierarchyObject.Name = name;
-        if (parent is not null)
-            hierarchyObject.SetParent(parent);
-        return hierarchyObject;
-    }
-
-    public static T? FindHierarchyObject<T>(this IEnumerable<IHierarchyObject> hierarchyObjects) where T : class
-    {
-        foreach (IHierarchyObject hierarchyObject in hierarchyObjects)
-            if (hierarchyObject is T @object)
-                return @object;
-
-        return default;
-    }
-
-    public static bool TryFindHierarchyObject<T>(this IEnumerable<IHierarchyObject> hierarchyObjects, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
-    {
-        behaviour = FindHierarchyObject<T>(hierarchyObjects);
-        return behaviour is not null;
-    }
-
-    public static void FindHierarchyObjects<T>(this IEnumerable<IHierarchyObject> hierarchyObjects, List<T> behaviours) where T : class
-    {
-        behaviours.Clear();
-        foreach (IHierarchyObject hierarchyObject in hierarchyObjects)
-            if (hierarchyObject is T @object)
-                behaviours.Add(@object);
-    }
-}

Engine.Core/Extensions/TransformExtensions.cs

@@ -1,6 +1,4 @@
-using Syntriax.Engine.Core.Abstract;
+namespace Engine.Core;
-
-namespace Syntriax.Engine.Core;
 
 public static class TransformExtensions
 {
@@ -16,4 +14,17 @@ public static class TransformExtensions
         if (localScale.HasValue) transform.LocalScale = localScale.Value;
         return transform;
     }
+
+    public static ITransform3D SetTransform(this ITransform3D transform,
+        Vector3D? position = null, Quaternion? rotation = null, Vector3D? scale = null,
+        Vector3D? localPosition = null, Quaternion? localRotation = null, Vector3D? localScale = null)
+    {
+        if (position.HasValue) transform.Position = position.Value;
+        if (rotation.HasValue) transform.Rotation = rotation.Value;
+        if (scale.HasValue) transform.Scale = scale.Value;
+        if (localPosition.HasValue) transform.LocalPosition = localPosition.Value;
+        if (localRotation.HasValue) transform.LocalRotation = localRotation.Value;
+        if (localScale.HasValue) transform.LocalScale = localScale.Value;
+        return transform;
+    }
 }

Engine.Core/Extensions/UniverseExtensions.cs

@@ -0,0 +1,36 @@
+using Engine.Core.Exceptions;
+
+namespace Engine.Core;
+
+public static class UniverseExtensions
+{
+    public static IUniverseObject InstantiateUniverseObject(this IUniverse universe, params object?[]? args)
+        => universe.InstantiateUniverseObject<UniverseObject>(args);
+
+    /// <summary>
+    /// Searches through all <see cref="IUniverseObject"/>s to find the specified instance of the type.
+    /// </summary>
+    /// <typeparam name="T">Type to be searched through the <see cref="IUniverse"/>.</typeparam>
+    /// <returns>The specified type if found; otherwise, throws <see cref="UniverseObjectNotFoundException"/>.</returns>
+    public static T GetRequiredUniverseObject<T>(this IUniverse universe) where T : class
+        => universe.GetUniverseObject<T>() ?? throw new UniverseObjectNotFoundException($"{universe.GetType().FullName}({universe.Id}) does not contain any {nameof(IUniverseObject)} object of type {typeof(T).FullName}");
+
+    /// <summary>
+    /// Searches through all <see cref="IBehaviours"/>s to find the specified instance of the type.
+    /// </summary>
+    /// <typeparam name="T">Type to be searched through the <see cref="IUniverse"/>.</typeparam>
+    /// <returns>The specified type if found; otherwise, throws <see cref="BehaviourNotFoundException"/>.</returns>
+    public static T FindRequiredBehaviour<T>(this IUniverse universe) where T : class
+        => universe.FindBehaviour<T>() ?? throw new BehaviourNotFoundException($"{universe.GetType().FullName}({universe.Id}) does not contain any {nameof(IUniverseObject)} with {nameof(IBehaviour)} of type {typeof(T).FullName}");
+
+    /// <summary>
+    /// Searches through all <see cref="IUniverseObject"/>s and <see cref="IBehaviours"/>s to find the specified instance of the type.
+    /// </summary>
+    /// <remarks>
+    /// WARNING: This is more expensive compared to <see cref="GetRequiredUniverseObject{T}(IUniverse)"/> or <see cref="FindRequiredBehaviour{T}(IUniverse)"/> as it combines the two. If you know whether the type is either a type that gets implemented on an <see cref="IBehaviour"/> or <see cref="IUniverseObject"/> use the method appropriate for it for performance.
+    /// </remarks>
+    /// <typeparam name="T">Type to be searched through the <see cref="IUniverse"/>.</typeparam>
+    /// <returns>The specified type if found; otherwise, throws <see cref="NotFoundException"/>.</returns>
+    public static T FindRequired<T>(this IUniverse universe) where T : class
+        => universe.Root.BehaviourController.GetBehaviourInChildren<T>() ?? throw new NotFoundException($"{universe.GetType().FullName}({universe.Id}) does not contain any {nameof(IUniverseObject)} or {nameof(IBehaviour)} of type {typeof(T).FullName}");
+}

Engine.Core/Extensions/UniverseObjectExtensions.cs

@@ -0,0 +1,270 @@
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
+using Engine.Core.Exceptions;
+
+namespace Engine.Core;
+
+public static class UniverseObjectExtensions
+{
+    public static T SetUniverseObject<T>(this T universeObject, string? name = "", IUniverseObject? parent = null) where T : IUniverseObject
+    {
+        if (!string.IsNullOrWhiteSpace(name))
+            universeObject.Name = name;
+        if (parent is not null)
+            universeObject.Parent = parent;
+        return universeObject;
+    }
+
+    public static IEnumerator<IUniverseObject> TraverseChildren(this IUniverseObject universeObject)
+    {
+        static IEnumerable<IUniverseObject> Traverse(IUniverseObject obj)
+        {
+            foreach (IUniverseObject child in obj.Children)
+            {
+                yield return child;
+                foreach (IUniverseObject descendant in Traverse(child))
+                    yield return descendant;
+            }
+        }
+
+        return Traverse(universeObject).GetEnumerator();
+    }
+
+    #region Universe Object Search
+    /// <summary>
+    /// Gets a <see cref="IUniverseObject"/> of the specified type.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObjects">The <see cref="IUniverseObject"/>s to search.</param>
+    /// <returns>The first found <see cref="IUniverseObject"/> of the specified type; otherwise, null.</returns>
+    public static T? GetUniverseObject<T>(this IEnumerable<IUniverseObject> universeObjects) where T : class
+    {
+        foreach (IUniverseObject universeObject in universeObjects)
+            if (universeObject is T @object)
+                return @object;
+
+        return default;
+    }
+
+    /// <summary>
+    /// Tries to get a <see cref="IUniverseObject"/> of the specified type.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObjects">The <see cref="IUniverseObject"/>s to search.</param>
+    /// <returns><see cref="true"/> if a <see cref="IUniverseObject"/> of the specified type was found in the universe objects; otherwise, <see cref="false"/>.</returns>
+    public static bool TryGetUniverseObject<T>(this IEnumerable<IUniverseObject> universeObjects, [NotNullWhen(returnValue: true)] out T? universeObject) where T : class
+    {
+        universeObject = GetUniverseObject<T>(universeObjects);
+        return universeObject is not null;
+    }
+
+    /// <summary>
+    /// Searches through the provided <see cref="IUniverseObject"/>s to collect a list of <see cref="IUniverseObject"/>s of the specified type.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to search.</param>
+    /// <returns>The found <see cref="IUniverseObject"/>s of the specified types</returns>
+    public static void GetUniverseObjects<T>(this IEnumerable<IUniverseObject> universeObjects, IList<T> foundUniverseObjects) where T : class
+    {
+        foundUniverseObjects.Clear();
+
+        foreach (IUniverseObject universeObject in universeObjects)
+            if (universeObject is T @object)
+                foundUniverseObjects.Add(@object);
+    }
+    #endregion
+
+    #region Universe Object Search In Parent
+    /// <summary>
+    /// Tries to get a <see cref="IUniverseObject"/> of the specified type in it's parents recursively.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="behaviour">When this method returns, contains the <see cref="IUniverseObject"/> of the specified type, if found; otherwise, null.</param>
+    /// <returns><see cref="true"/> if a <see cref="IUniverseObject"/> of the specified type was found in the parent universe objects; otherwise, <see cref="false"/>.</returns>
+    public static bool TryGetUniverseObjectInParent<T>(this IUniverseObject universeObject, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
+    {
+        behaviour = GetUniverseObjectInParent<T>(universeObject);
+        return behaviour is not null;
+    }
+
+    /// <summary>
+    /// Gets a <see cref="IUniverseObject"/> of the specified type in it's parents recursively.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to start searching from.</param>
+    /// <returns>The <see cref="IUniverseObject"/> of the specified type if found; otherwise, null.</returns>
+    public static T? GetUniverseObjectInParent<T>(this IUniverseObject universeObject) where T : class
+    {
+        if (universeObject.Children.GetUniverseObject<T>() is T localUniverseObject)
+            return localUniverseObject;
+
+        IUniverseObject? parent = universeObject;
+
+        while (parent is not null)
+        {
+            if (parent is T behaviour)
+                return behaviour;
+
+            parent = universeObject.Parent;
+        }
+
+        return default;
+    }
+
+    /// <summary>
+    /// Gets a <see cref="IUniverseObject"/> of the specified type in the parents recursively. Throws an error if not found.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to start searching from.</param>
+    /// <returns>The <see cref="IUniverseObject"/> of the specified type if found; otherwise, throws <see cref="UniverseObjectNotFoundException"/>.</returns>
+    public static T GetRequiredUniverseObjectInParent<T>(this IUniverseObject universeObject) where T : class
+        => universeObject.GetUniverseObjectInParent<T>() ?? throw new UniverseObjectNotFoundException($"{universeObject.Name}'s {nameof(IUniverseObject)} does not contain any {typeof(T).FullName} on any parent ");
+
+    #endregion
+
+    #region Universe Object Search In Children
+    /// <summary>
+    /// Tries to get a <see cref="IUniverseObject"/> of the specified type in it's children recursively.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="behaviour">When this method returns, contains the <see cref="IUniverseObject"/> of the specified type, if found; otherwise, null.</param>
+    /// <returns><see cref="true"/> if a <see cref="IUniverseObject"/> of the specified type was found in the child universe objects; otherwise, <see cref="false"/>.</returns>
+    public static bool TryGetUniverseObjectInChildren<T>(this IUniverseObject universeObject, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
+    {
+        behaviour = GetUniverseObjectInChildren<T>(universeObject);
+        return behaviour is not null;
+    }
+
+    /// <summary>
+    /// Gets a <see cref="IUniverseObject"/> of the specified type in it's children recursively.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to start searching from.</param>
+    /// <returns>The <see cref="IUniverseObject"/> of the specified type if found; otherwise, null.</returns>
+    public static T? GetUniverseObjectInChildren<T>(this IUniverseObject universeObject) where T : class
+    {
+        if (universeObject.Children.GetUniverseObject<T>() is T localUniverseObject)
+            return localUniverseObject;
+
+        foreach (IUniverseObject child in universeObject.Children)
+            if (GetUniverseObjectInChildren<T>(child) is T behaviour)
+                return behaviour;
+
+        return default;
+    }
+
+    /// <summary>
+    /// Gets a <see cref="IUniverseObject"/> of the specified type in the children recursively. Throws an error if not found.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IUniverseObject"/> to get.</typeparam>
+    /// <param name="universeObject">The <see cref="IUniverseObject"/> to start searching from.</param>
+    /// <returns>The <see cref="IUniverseObject"/> of the specified type if found; otherwise, throws <see cref="UniverseObjectNotFoundException"/>.</returns>
+    public static T GetRequiredUniverseObjectInChildren<T>(this IUniverseObject universeObject) where T : class
+        => universeObject.GetUniverseObjectInChildren<T>() ?? throw new UniverseObjectNotFoundException($"{universeObject.Name}'s {nameof(IUniverseObject)} does not contain any {typeof(T).FullName} on any children ");
+    #endregion
+
+    #region Behaviour Search
+    /// <summary>
+    /// Finds a <see cref="IBehaviour"/> of the specified type in the provided <see cref="IUniverseObject"/>s.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to find.</typeparam>
+    /// <returns>The first found <see cref="IBehaviour"/> of the specified type; otherwise, null.</returns>
+    public static T? FindBehaviour<T>(this IEnumerable<IUniverseObject> universeObjects) where T : class
+    {
+        foreach (IUniverseObject universeObject in universeObjects)
+            if (universeObject.BehaviourController.GetBehaviour<T>() is T behaviour)
+                return behaviour;
+
+        return default;
+    }
+
+    /// <summary>
+    /// Tries to find a <see cref="IBehaviour"/> of the specified type in the provided <see cref="IUniverseObject"/>s.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to find.</typeparam>
+    /// <param name="behaviour">When this method returns, contains the <see cref="IUniverseObject"/> of the specified type, if found; otherwise, null.</param>
+    /// <returns><see cref="true"/> if a <see cref="IBehaviour"/> of the specified type was found in the provided <see cref="IUniverseObject"/>s; otherwise, <see cref="false"/>.</returns>
+    public static bool TryFindBehaviour<T>(this IEnumerable<IUniverseObject> universeObjects, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
+    {
+        behaviour = FindBehaviour<T>(universeObjects);
+        return behaviour is not null;
+    }
+
+    /// <summary>
+    /// Searches through the provided <see cref="IUniverseObject"/>s to collect a list of <see cref="IBehaviour"/>s of the specified type.
+    /// </summary>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <param name="universeObjects">The <see cref="IUniverseObject"/>s to search.</param>
+    public static void FindBehaviours<T>(this IEnumerable<IUniverseObject> universeObjects, IList<T> behaviours) where T : class
+    {
+        behaviours.Clear();
+        List<T> cache = [];
+
+        foreach (IUniverseObject universeObject in universeObjects)
+        {
+            universeObject.BehaviourController.GetBehaviours(cache);
+            foreach (T behaviour in cache)
+                behaviours.Add(behaviour);
+        }
+    }
+    #endregion
+
+    #region General Search
+    /// <summary>
+    /// Finds an object of the specified type in the provided <see cref="IUniverseObject"/>s and their <see cref="IBehaviour"/>s.
+    /// </summary>
+    /// <remarks>
+    /// WARNING: This is more expensive compared to <see cref="GetUniverseObject{T}(IEnumerable{IUniverseObject})"/> or <see cref="FindBehaviour{T}(IEnumerable{IUniverseObject})"/> as it combines the two. If you know whether the type is either a type that gets implemented on an <see cref="IBehaviour"/> or <see cref="IUniverseObject"/> use the method appropriate for it for performance.
+    /// </remarks>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to find.</typeparam>
+    /// <returns>The first found instance of the specified type; otherwise, null.</returns>
+    public static T? Find<T>(this IEnumerable<IUniverseObject> universeObjects) where T : class
+    {
+        if (universeObjects.GetUniverseObject<T>() is T foundUniverseObject)
+            return foundUniverseObject;
+
+        if (universeObjects.FindBehaviour<T>() is T foundBehaviour)
+            return foundBehaviour;
+
+        return null;
+    }
+
+    /// <summary>
+    /// Tries to find an object of the specified type in the provided <see cref="IUniverseObject"/>s and their <see cref="IBehaviour"/>s.
+    /// </summary>
+    /// <remarks>
+    /// WARNING: This is more expensive compared to <see cref="TryGetUniverseObject{T}(IEnumerable{IUniverseObject}, out T?)"/> or <see cref="TryFindBehaviour{T}(IEnumerable{IUniverseObject}, out T?)"/> as it combines the two. If you know whether the type is either a type that gets implemented on an <see cref="IBehaviour"/> or <see cref="IUniverseObject"/> use the method appropriate for it for performance.
+    /// </remarks>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to find.</typeparam>
+    /// <param name="behaviour">When this method returns, contains the <see cref="IUniverseObject"/> of the specified type, if found; otherwise, null.</param>
+    /// <returns><see cref="true"/> if an object of the specified type was found in the provided <see cref="IUniverseObject"/>s; otherwise, <see cref="false"/>.</returns>
+    public static bool TryFind<T>(this IEnumerable<IUniverseObject> universeObjects, [NotNullWhen(returnValue: true)] out T? behaviour) where T : class
+    {
+        behaviour = Find<T>(universeObjects);
+        return behaviour is not null;
+    }
+
+    /// <summary>
+    /// Searches through the provided <see cref="IUniverseObject"/>s and their <see cref="IBehaviour"/>s to collect a list of the specified type.
+    /// </summary>
+    /// <remarks>
+    /// WARNING: This is more expensive compared to <see cref="GetUniverseObjects{T}(IEnumerable{IUniverseObject}, IList{T})"/> or <see cref="FindBehaviours{T}(IEnumerable{IUniverseObject}, IList{T})"/> as it combines the two. If you know whether the type is either a type that gets implemented on an <see cref="IBehaviour"/> or <see cref="IUniverseObject"/> use the method appropriate for it for performance.
+    /// </remarks>
+    /// <typeparam name="T">The type of <see cref="IBehaviour"/> to get.</typeparam>
+    /// <param name="instances">List of objects found wit the specified type.</param>
+    /// <param name="universeObjects">The <see cref="IUniverseObject"/>s to search.</param>
+    public static void Find<T>(this IEnumerable<IUniverseObject> universeObjects, IList<T> instances) where T : class
+    {
+        instances.Clear();
+        List<T> cache = [];
+
+        foreach (IUniverseObject universeObject in universeObjects)
+        {
+            universeObject.Children.Find(cache);
+            foreach (T behaviour in cache)
+                instances.Add(behaviour);
+        }
+    }
+    #endregion
+}

Engine.Core/Factory/Abstract/IFactory.cs

@@ -1,4 +1,4 @@
-namespace Syntriax.Engine.Core.Factory.Abstract;
+namespace Engine.Core.Factory.Abstract;
 
 public interface IFactory<TInterface> where TInterface : class
 {

Engine.Core/Factory/BehaviourControllerFactory.cs

@@ -1,23 +1,33 @@
-using Syntriax.Engine.Core.Abstract;
+using Engine.Core.Exceptions;
-using Syntriax.Engine.Core.Exceptions;
 
-namespace Syntriax.Engine.Core.Factory;
+namespace Engine.Core.Factory;
 
 public class BehaviourControllerFactory
 {
-    public static IBehaviourController Instantiate(IHierarchyObject hierarchyObject)
+    public static IBehaviourController Instantiate(IUniverseObject universeObject, IStateEnable? stateEnable = null)
-        => Instantiate<BehaviourController>(hierarchyObject);
+        => Instantiate<BehaviourController>(universeObject, stateEnable);
 
-    public static T Instantiate<T>(IHierarchyObject hierarchyObject, params object?[]? args)
+    public static T Instantiate<T>(IUniverseObject universeObject, IStateEnable? stateEnable = null, params object?[]? args)
         where T : class, IBehaviourController
     {
         T behaviourController = TypeFactory.Get<T>(args);
 
-        if (!hierarchyObject.Assign(behaviourController))
+        if (!universeObject.Assign(behaviourController))
-            throw AssignException.From(hierarchyObject, behaviourController);
+            throw AssignFailedException.From(universeObject, behaviourController);
 
-        if (!behaviourController.Assign(hierarchyObject))
+        if (!behaviourController.Assign(universeObject))
-            throw AssignException.From(behaviourController, hierarchyObject);
+            throw AssignFailedException.From(behaviourController, universeObject);
+
+        if (stateEnable is not null)
+        {
+            if (!stateEnable.Assign(behaviourController))
+                throw AssignFailedException.From(stateEnable, behaviourController);
+
+            if (!behaviourController.Assign(stateEnable))
+                throw AssignFailedException.From(behaviourController, stateEnable);
+        }
+        else
+            StateEnableFactory.Instantiate(behaviourController);
 
         return behaviourController;
     }

Engine.Core/Factory/BehaviourFactory.cs

@@ -1,26 +1,26 @@
-using Syntriax.Engine.Core.Abstract;
+using Engine.Core.Exceptions;
-using Syntriax.Engine.Core.Exceptions;
 
-namespace Syntriax.Engine.Core.Factory;
+namespace Engine.Core.Factory;
 
 public class BehaviourFactory
 {
-    public static T Instantiate<T>(IHierarchyObject hierarchyObject, params object?[]? args) where T : class, IBehaviour
+    public static T Instantiate<T>(params object?[]? args) where T : class, IBehaviour
-        => Instantiate<T>(hierarchyObject, stateEnable: null, args);
+        => Instantiate<T>(stateEnable: null, args);
 
-    public static T Instantiate<T>(IHierarchyObject hierarchyObject, IStateEnable? stateEnable, params object?[]? args)
+    public static T Instantiate<T>(IStateEnable? stateEnable, params object?[]? args)
         where T : class, IBehaviour
     {
         T behaviour = TypeFactory.Get<T>(args);
 
-        stateEnable ??= TypeFactory.Get<StateEnable>();
+        if (stateEnable is not null)
+        {
             if (!stateEnable.Assign(behaviour))
-            throw AssignException.From(stateEnable, behaviour);
+                throw AssignFailedException.From(stateEnable, behaviour);
-
             if (!behaviour.Assign(stateEnable))
-            throw AssignException.From(behaviour, stateEnable);
+                throw AssignFailedException.From(behaviour, stateEnable);
-        if (!behaviour.Assign(hierarchyObject.BehaviourController))
+        }
-            throw AssignException.From(behaviour, hierarchyObject.BehaviourController);
+        else
+            StateEnableFactory.Instantiate(behaviour);
 
         return behaviour;
     }

Engine.Core/Factory/FactoryBase.cs

@@ -1,7 +1,7 @@
 using System;
-using Syntriax.Engine.Core.Factory.Abstract;
+using Engine.Core.Factory.Abstract;
 
-namespace Syntriax.Engine.Core.Factory;
+namespace Engine.Core.Factory;
 
 public abstract class FactoryBase<TInterface> : IFactory<TInterface>
     where TInterface : class

Engine.Core/Factory/HierarchyObjectFactory.cs

@@ -1,37 +0,0 @@
-using Syntriax.Engine.Core.Abstract;
-using Syntriax.Engine.Core.Exceptions;
-
-namespace Syntriax.Engine.Core.Factory;
-
-public class HierarchyObjectFactory
-{
-    public static IHierarchyObject Instantiate() => Instantiate<HierarchyObject>();
-    public static T Instantiate<T>(params object?[]? args) where T : class, IHierarchyObject
-        => Instantiate<T>(behaviourController: null, stateEnable: null, args);
-
-    public static IHierarchyObject Instantiate(IBehaviourController? behaviourController = null, IStateEnable? stateEnable = null) => Instantiate<HierarchyObject>(behaviourController, stateEnable);
-    public static T Instantiate<T>(
-        IBehaviourController? behaviourController = null,
-        IStateEnable? stateEnable = null,
-        params object?[]? args
-    )
-        where T : class, IHierarchyObject
-    {
-        T hierarchyObject = TypeFactory.Get<T>(args);
-
-        behaviourController ??= TypeFactory.Get<BehaviourController>();
-        stateEnable ??= TypeFactory.Get<StateEnable>();
-
-        if (!behaviourController.Assign(hierarchyObject))
-            throw AssignException.From(behaviourController, hierarchyObject);
-        if (!stateEnable.Assign(hierarchyObject))
-            throw AssignException.From(stateEnable, hierarchyObject);
-
-        if (!hierarchyObject.Assign(behaviourController))
-            throw AssignException.From(hierarchyObject, behaviourController);
-        if (!hierarchyObject.Assign(stateEnable))
-            throw AssignException.From(hierarchyObject, stateEnable);
-
-        return hierarchyObject;
-    }
-}

Engine.Core/Factory/StateEnableFactory.cs

@@ -1,7 +1,6 @@
-using Syntriax.Engine.Core.Abstract;
+using Engine.Core.Exceptions;
-using Syntriax.Engine.Core.Exceptions;
 
-namespace Syntriax.Engine.Core.Factory;
+namespace Engine.Core.Factory;
 
 public class StateEnableFactory
 {
@@ -12,10 +11,10 @@ public class StateEnableFactory
         T stateEnable = TypeFactory.Get<T>(args);
 
         if (!entity.Assign(stateEnable))
-            throw AssignException.From(entity, stateEnable);
+            throw AssignFailedException.From(entity, stateEnable);
 
         if (!stateEnable.Assign(entity))
-            throw AssignException.From(stateEnable, entity);
+            throw AssignFailedException.From(stateEnable, entity);
 
         return stateEnable;
     }

Engine.Core/Factory/TransformFactory.cs

@@ -1,6 +1,4 @@
-using Syntriax.Engine.Core.Abstract;
+namespace Engine.Core.Factory;
-
-namespace Syntriax.Engine.Core.Factory;
 
 public class TransformFactory
 {

Engine.Core/Factory/TypeFactory.cs

@@ -1,21 +1,59 @@
 using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
 
-namespace Syntriax.Engine.Core.Factory;
+namespace Engine.Core.Factory;
 
 public static class TypeFactory
 {
-    public static T Get<T>(params object?[]? args) where T : class
+    private static readonly ConcurrentDictionary<string, Type> registeredTypes = [];
+
+    public static string GetTypeName(Type type) => type.FullName ?? throw new ArgumentException($"{type.Name} must be a resolvable type");
+
+    public static T Get<T>(params object?[]? args) where T : class => (T)Get(typeof(T), args);
+    public static object Get(string fullName, params object?[]? args) => Get(GetType(fullName), args);
+    public static object Get(Type type, params object?[]? args)
     {
-        T? result;
+        object? result;
 
         if (args is not null && args.Length != 0)
-            result = Activator.CreateInstance(typeof(T), args) as T;
+            result = Activator.CreateInstance(type, args);
         else
-            result = Activator.CreateInstance(typeof(T)) as T;
+            result = Activator.CreateInstance(type);
 
         if (result is null)
-            throw new Exception($"{typeof(T).Name} of type {typeof(T).Name} could not be created.");
+            throw new Exception($"Type {type.Name} could not be created.");
 
         return result;
     }
+
+    public static Type GetType(string fullName)
+    {
+        if (registeredTypes.TryGetValue(fullName, out Type? result))
+            return result;
+
+        ReloadTypes();
+
+        if (registeredTypes.TryGetValue(fullName, out Type? reloadedType))
+            return reloadedType;
+
+        throw new Exception($"Type {fullName} could not be found in the current domain.");
+    }
+
+    public static void ReloadTypes()
+    {
+        registeredTypes.Clear();
+
+        IEnumerable<Type> domainTypes = AppDomain.CurrentDomain
+            .GetAssemblies()
+            .SelectMany(a => a.GetTypes());
+
+        // TODO: Replace this
+        // There are some system & compiler generated types with duplicated names, 
+        // it is ugly it will cause headaches in the future because it will not 
+        // throw an error if there's a type with an unintended duplicate name
+        foreach (Type type in domainTypes)
+            registeredTypes.TryAdd(GetTypeName(type), type);
+    }
 }

Engine.Core/Factory/UniverseObjectFactory.cs

@@ -0,0 +1,43 @@
+using Engine.Core.Exceptions;
+
+namespace Engine.Core.Factory;
+
+public class UniverseObjectFactory
+{
+    public static IUniverseObject Instantiate() => Instantiate<UniverseObject>();
+    public static T Instantiate<T>(params object?[]? args) where T : class, IUniverseObject
+        => Instantiate<T>(behaviourController: null, stateEnable: null, args);
+
+    public static IUniverseObject Instantiate(IBehaviourController? behaviourController = null, IStateEnable? stateEnable = null) => Instantiate<UniverseObject>(behaviourController, stateEnable);
+    public static T Instantiate<T>(
+        IBehaviourController? behaviourController = null,
+        IStateEnable? stateEnable = null,
+        params object?[]? args
+    )
+        where T : class, IUniverseObject
+    {
+        T universeObject = TypeFactory.Get<T>(args);
+
+        if (behaviourController is not null)
+        {
+            if (!behaviourController.Assign(universeObject))
+                throw AssignFailedException.From(behaviourController, universeObject);
+            if (!universeObject.Assign(behaviourController))
+                throw AssignFailedException.From(universeObject, behaviourController);
+        }
+        else
+            BehaviourControllerFactory.Instantiate(universeObject);
+
+        if (stateEnable is not null)
+        {
+            if (!stateEnable.Assign(universeObject))
+                throw AssignFailedException.From(stateEnable, universeObject);
+            if (!universeObject.Assign(stateEnable))
+                throw AssignFailedException.From(universeObject, stateEnable);
+        }
+        else
+            StateEnableFactory.Instantiate(universeObject);
+
+        return universeObject;
+    }
+}

Engine.Core/GameManager.cs

@@ -1,143 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-using Syntriax.Engine.Core.Abstract;
-using Syntriax.Engine.Core.Exceptions;
-
-namespace Syntriax.Engine.Core;
-
-[System.Diagnostics.DebuggerDisplay("HierarchyObject Count: {_hierarchyObjects.Count}")]
-public class GameManager : BaseEntity, IGameManager
-{
-    public event IGameManager.UpdateEventHandler? OnPreUpdate = null;
-    public event IGameManager.UpdateEventHandler? OnUpdate = null;
-    public event IGameManager.PreDrawEventHandler? OnPreDraw = null;
-
-    public event IGameManager.HierarchyObjectRegisteredEventHandler? OnHierarchyObjectRegistered = null;
-    public event IGameManager.HierarchyObjectUnRegisteredEventHandler? OnHierarchyObjectUnRegistered = null;
-
-    private readonly List<IHierarchyObject> _hierarchyObjects = new(Constants.GAME_OBJECTS_SIZE_INITIAL);
-
-    public IReadOnlyList<IHierarchyObject> HierarchyObjects => _hierarchyObjects;
-
-    public override IStateEnable StateEnable
-    {
-        get
-        {
-            if (base.StateEnable is null)
-            {
-                Assign(Factory.StateEnableFactory.Instantiate(this));
-                if (base.StateEnable is null)
-                    throw NotAssignedException.From(this, base.StateEnable);
-            }
-
-            return base.StateEnable;
-        }
-    }
-
-    public EngineTime Time { get; private set; } = new();
-
-    public void Register(IHierarchyObject hierarchyObject)
-    {
-        if (_hierarchyObjects.Contains(hierarchyObject))
-            throw new Exception($"{nameof(IHierarchyObject)} named {hierarchyObject.Name} is already registered to the {nameof(GameManager)}.");
-
-        hierarchyObject.OnFinalized += OnHierarchyObjectFinalize;
-        hierarchyObject.OnExitedHierarchy += OnHierarchyObjectExitedHierarchy;
-
-        if (!hierarchyObject.Initialize())
-            throw new Exception($"{hierarchyObject.Name} can't be initialized");
-
-        for (int i = 0; i < hierarchyObject.Children.Count; i++)
-            Register(hierarchyObject.Children[i]);
-
-        _hierarchyObjects.Add(hierarchyObject);
-
-        if (!hierarchyObject.EnterHierarchy(this))
-            throw new Exception($"{hierarchyObject.Name} can't enter the hierarchy");
-
-        OnHierarchyObjectRegistered?.Invoke(this, hierarchyObject);
-    }
-
-    public T InstantiateHierarchyObject<T>(params object?[]? args) where T : class, IHierarchyObject
-    {
-        T hierarchyObject = Factory.HierarchyObjectFactory.Instantiate<T>(args);
-        Register(hierarchyObject);
-        return hierarchyObject;
-    }
-
-    public void Remove(IHierarchyObject hierarchyObject)
-    {
-        if (!_hierarchyObjects.Contains(hierarchyObject))
-            throw new Exception($"{nameof(IHierarchyObject)} named {hierarchyObject.Name} is not registered to the {nameof(GameManager)}.");
-
-        hierarchyObject.OnFinalized -= OnHierarchyObjectFinalize;
-        hierarchyObject.OnExitedHierarchy -= OnHierarchyObjectExitedHierarchy;
-
-        for (int i = hierarchyObject.Children.Count - 1; i >= 0; i--)
-            Remove(hierarchyObject.Children[i]);
-
-        _hierarchyObjects.Remove(hierarchyObject);
-        hierarchyObject.SetParent(null);
-
-        if (!hierarchyObject.ExitHierarchy())
-            throw new Exception($"{hierarchyObject.Name} can't exit the hierarchy");
-
-        if (!hierarchyObject.Finalize())
-            throw new Exception($"{hierarchyObject.Name} can't be finalized");
-
-        OnHierarchyObjectUnRegistered?.Invoke(this, hierarchyObject);
-    }
-
-    protected override void InitializeInternal()
-    {
-        base.InitializeInternal();
-        NotAssignedException.Check(this, StateEnable);
-
-        foreach (IHierarchyObject hierarchyObject in HierarchyObjects)
-            hierarchyObject.Initialize();
-    }
-
-    protected override void FinalizeInternal()
-    {
-        base.FinalizeInternal();
-        for (int i = HierarchyObjects.Count; i >= 0; i--)
-            HierarchyObjects[i].Finalize();
-    }
-
-    public void Update(EngineTime engineTime)
-    {
-        Time = engineTime;
-
-        OnPreUpdate?.Invoke(this, engineTime);
-
-        for (int i = 0; i < HierarchyObjects.Count; i++)
-            HierarchyObjects[i].BehaviourController.Update();
-
-        OnUpdate?.Invoke(this, engineTime);
-    }
-
-    public void PreDraw()
-    {
-        for (int i = 0; i < HierarchyObjects.Count; i++)
-            HierarchyObjects[i].BehaviourController.UpdatePreDraw();
-
-        OnPreDraw?.Invoke(this);
-    }
-
-    private void OnHierarchyObjectFinalize(IInitializable initializable)
-    {
-        if (initializable is IHierarchyObject hierarchyObject)
-            Remove(hierarchyObject);
-    }
-
-    private void OnHierarchyObjectExitedHierarchy(IHierarchyObject sender, IGameManager gameManager)
-    {
-        if (sender is IHierarchyObject hierarchyObject)
-            Remove(hierarchyObject);
-    }
-
-    public IEnumerator<IHierarchyObject> GetEnumerator() => _hierarchyObjects.GetEnumerator();
-    IEnumerator IEnumerable.GetEnumerator() => _hierarchyObjects.GetEnumerator();
-}

Engine.Core/Helpers/Event.cs

@@ -0,0 +1,506 @@
+using System;
+using System.Collections.Generic;
+
+using Engine.Core.Debug;
+
+namespace Engine.Core;
+
+// TODO!: every reverse loop has a chance to have more than 1 unsubscription,
+// for (int i = listeners.Count - 1; i >= 0; i--) 
+// can be replaced with 
+// for (int i = listeners.Count - 1; i >= 0; i = Math.Min(i - 1, listeners.Count - 1))
+// but this would causes possible double calls on already called callbacks, find a better method.
+
+/// <summary>
+/// Represents a simple event with no parameters.
+/// <para>Example usage:</para> 
+/// <code>
+/// public class MyBehaviour : Behaviour, IUpdate
+/// {
+///     public readonly Event MyEvent = new();
+/// 
+///     public MyBehaviour()
+///     {
+///         MyEvent.AddListener(OnEventTriggered);
+///         MyEvent.AddOneTimeListener(OnEventTriggeredOneTime);
+///     }
+/// 
+///     public void Update()
+///     {
+///         MyEvent.Invoke();
+///     }
+/// 
+///     private void OnEventTriggered()
+///     {
+///         Console.WriteLine($"Event occurred!");
+///     }
+/// 
+///     private static void OnEventTriggeredOneTime()
+///     {
+///         Console.WriteLine($"Event called once!");
+///     }
+/// }
+/// </code>
+/// The output of the example code above would be: 
+/// <code>
+/// Event occurred!
+/// Event called once!
+/// Event occurred!
+/// Event occurred!
+/// Event occurred!
+/// ...
+/// </code>
+/// </summary>
+public class Event
+{
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private ILogger _logger = ILogger.Shared;
+    public ILogger Logger { get => _logger; set => _logger = value ?? ILogger.Shared; }
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
+
+    /// <summary>
+    /// Subscribes the callback to be invoked whenever the event is triggered.
+    /// </summary>
+    /// <param name="listener">The callback to be called when the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
+    /// </summary>
+    /// <param name="listener">The callback to be called the next time the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    public void Clear() { listeners.Clear(); onceListeners.Clear(); }
+
+    /// <summary>
+    /// Triggers the event.
+    /// </summary>
+    public void Invoke()
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            try { listeners[i].Callback.Invoke(); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}()";
+                EventHelpers.LogInvocationException(listeners[i].Callback.Target ?? this, Logger, exception, methodCallRepresentation);
+            }
+
+        for (int i = onceListeners.Count - 1; i >= 0; i--)
+        {
+            try { onceListeners[i].Callback.Invoke(); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}()";
+                EventHelpers.LogInvocationException(onceListeners[i].Callback.Target ?? this, Logger, exception, methodCallRepresentation);
+            }
+            onceListeners.RemoveAt(i);
+        }
+    }
+
+    public Event(int initialListenerCount = 4, int initialOnceListenerCount = 2)
+    {
+        listeners = new(initialListenerCount);
+        onceListeners = new(initialOnceListenerCount);
+    }
+
+    public Event()
+    {
+        listeners = new(4);
+        onceListeners = new(2);
+    }
+
+    public delegate void EventHandler();
+    private record struct ListenerData(EventHandler Callback, int Priority);
+}
+
+/// <summary>
+/// Represents an event with only sender parameters.
+/// <para>Example usage:</para> 
+/// <code>
+/// public class MyBehaviour : Behaviour, IUpdate
+/// {
+///     public readonly Event&lt;MyBehaviour&gt; MyEvent = new();
+/// 
+///     public MyBehaviour()
+///     {
+///         MyEvent.AddListener(OnEventTriggered);
+///         MyEvent.AddOneTimeListener(OnEventTriggeredOneTime);
+///     }
+/// 
+///     public void Update()
+///     {
+///         MyEvent.Invoke(this);
+///     }
+/// 
+///     private void OnEventTriggered(MyBehaviour sender)
+///     {
+///         Console.WriteLine($"{sender.Id}'s event occurred!");
+///     }
+/// 
+///     private static void OnEventTriggeredOneTime(MyBehaviour sender)
+///     {
+///         Console.WriteLine($"{sender.Id}'s event called once!");
+///     }
+/// }
+/// </code>
+/// The output of the example code above would be: 
+/// <code>
+/// [Id]'s event occurred!
+/// [Id]'s event called once!
+/// [Id]'s event occurred!
+/// [Id]'s event occurred!
+/// [Id]'s event occurred!
+/// ...
+/// </code>
+/// 
+/// </summary>
+/// <typeparam name="TSender">Sender type</typeparam>
+public class Event<TSender> where TSender : class
+{
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private ILogger _logger = ILogger.Shared;
+    public ILogger Logger { get => _logger; set => _logger = value ?? ILogger.Shared; }
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
+
+    /// <summary>
+    /// Subscribes the callback to be invoked whenever the event is triggered.
+    /// </summary>
+    /// <param name="listener">The callback to be called when the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
+    /// </summary>
+    /// <param name="listener">The callback to be called the next time the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    public void Clear() { listeners.Clear(); onceListeners.Clear(); }
+
+    /// <summary>
+    /// Triggers the event.
+    /// </summary>
+    /// <param name="sender">The caller that's triggering this event.</param>
+    public void Invoke(TSender sender)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            try { listeners[i].Callback.Invoke(sender); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}({sender})";
+                EventHelpers.LogInvocationException(listeners[i].Callback.Target ?? sender, Logger, exception, methodCallRepresentation);
+            }
+
+        for (int i = onceListeners.Count - 1; i >= 0; i--)
+        {
+            try { onceListeners[i].Callback.Invoke(sender); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}({sender})";
+                EventHelpers.LogInvocationException(onceListeners[i].Callback.Target ?? sender, Logger, exception, methodCallRepresentation);
+            }
+            onceListeners.RemoveAt(i);
+        }
+    }
+
+    public Event(int initialListenerCount = 4, int initialOnceListenerCount = 2)
+    {
+        listeners = new(initialListenerCount);
+        onceListeners = new(initialOnceListenerCount);
+    }
+
+    public Event()
+    {
+        listeners = new(4);
+        onceListeners = new(2);
+    }
+
+    public delegate void EventHandler(TSender sender);
+    private record struct ListenerData(EventHandler Callback, int Priority);
+}
+
+/// <summary>
+/// Represents an event with sender and argument parameters.
+/// <para>Example usage:</para> 
+/// <code>
+/// public class MyBehaviour : Behaviour, IUpdate
+/// {
+///     public readonly Event&lt;MyBehaviour, MyArguments&gt; MyEvent = new();
+/// 
+///     private int myInt = 0;
+///     private bool myBool = false;
+/// 
+///     public MyBehaviour()
+///     {
+///         MyEvent.AddOneTimeListener(OnEventTriggeredOneTime);
+///         MyEvent.AddListener(OnEventTriggered);
+///     }
+/// 
+///     public void Update()
+///     {
+///         MyEvent.Invoke(this, new MyArguments(myInt, myBool));
+///         myInt++;
+///         myBool = !myBool;
+///     }
+/// 
+///     private void OnEventTriggered(MyBehaviour sender, MyArguments args)
+///     {
+///         Console.WriteLine($"{sender.Id}'s event occurred with MyInt: {args.MyInt} and MyBool {args.MyBool}!");
+///     }
+/// 
+///     private static void OnEventTriggeredOneTime(MyBehaviour sender, MyArguments args)
+///     {
+///         Console.WriteLine($"{sender.Id}'s event called once with MyInt: {args.MyInt} and MyBool {args.MyBool}!");
+///     }
+/// 
+///     public readonly record struct MyArguments(int MyInt, bool MyBool);
+/// }
+/// </code>
+/// The output of the example code above would be: 
+/// <code>
+/// [Id]'s event occurred with MyInt: 0 and MyBool False!
+/// [Id]'s event called once with MyInt: 0 and MyBool False!
+/// [Id]'s event occurred with MyInt: 1 and MyBool True!
+/// [Id]'s event occurred with MyInt: 2 and MyBool False!
+/// [Id]'s event occurred with MyInt: 3 and MyBool True!
+/// ...
+/// </code>
+/// 
+/// </summary>
+/// <typeparam name="TSender">Sender type</typeparam>
+public class Event<TSender, TArguments> where TSender : class
+{
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private ILogger _logger = ILogger.Shared;
+    public ILogger Logger { get => _logger; set => _logger = value ?? ILogger.Shared; }
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
+
+    /// <summary>
+    /// Subscribes the callback to be invoked whenever the event is triggered.
+    /// </summary>
+    /// <param name="listener">The callback to be called when the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
+    /// </summary>
+    /// <param name="listener">The callback to be called the next time the event is triggered.</param>
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
+
+    /// <summary>
+    /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
+    /// </summary>
+    public void Clear() { listeners.Clear(); onceListeners.Clear(); }
+
+    /// <summary>
+    /// Triggers the event.
+    /// </summary>
+    /// <param name="sender">The caller that's triggering this event.</param>
+    /// <param name="args">The arguments provided for this event.</param>
+    public void Invoke(TSender sender, TArguments args)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            try { listeners[i].Callback.Invoke(sender, args); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}({sender}, {args})";
+                EventHelpers.LogInvocationException(listeners[i].Callback.Target ?? sender, Logger, exception, methodCallRepresentation);
+            }
+
+        for (int i = onceListeners.Count - 1; i >= 0; i--)
+        {
+            try { onceListeners[i].Callback.Invoke(sender, args); }
+            catch (Exception exception)
+            {
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}({sender}, {args})";
+                EventHelpers.LogInvocationException(onceListeners[i].Callback.Target ?? sender, Logger, exception, methodCallRepresentation);
+            }
+            onceListeners.RemoveAt(i);
+        }
+    }
+
+    public Event(int initialListenerCount = 4, int initialOnceListenerCount = 2)
+    {
+        listeners = new(initialListenerCount);
+        onceListeners = new(initialOnceListenerCount);
+    }
+
+    public Event()
+    {
+        listeners = new(4);
+        onceListeners = new(2);
+    }
+
+    public delegate void EventHandler(TSender sender, TArguments args);
+    private record struct ListenerData(EventHandler Callback, int Priority);
+}
+
+internal static class EventHelpers
+{
+    public static void LogInvocationException(object sender, ILogger logger, Exception exception, string methodCallRepresentation)
+    {
+        logger.LogException(sender, exception);
+        logger.LogError(sender, $"Unexpected exception on invocation of method {methodCallRepresentation}");
+    }
+}

Engine.Core/Helpers/FastList.cs

@@ -0,0 +1,102 @@
+using System.Collections;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public class FastList<T> : IList<T>, IReadOnlyList<T>, IEnumerable<T> where T : notnull
+{
+    private readonly List<T> items = [];
+    private readonly Dictionary<T, int> indexMap = [];
+
+    public bool IsReadOnly { get; set; } = false;
+    public int Count => items.Count;
+    public T this[int index]
+    {
+        get => items[index];
+        set
+        {
+            if (IsReadOnly)
+                throw new System.Data.ReadOnlyException();
+
+            items[index] = value;
+        }
+    }
+
+    public void Add(T item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        indexMap[item] = items.Count;
+        items.Add(item);
+    }
+
+    public void RemoveAt(int i) => Remove(items[i], i);
+    public bool Remove(T item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        if (!indexMap.TryGetValue(item, out int index))
+            return false;
+
+        Remove(item, index);
+
+        return true;
+    }
+
+    private void Remove(T item, int index)
+    {
+        int lastIndex = items.Count - 1;
+        T lastItem = items[lastIndex];
+
+        items[index] = lastItem;
+        indexMap[lastItem] = index;
+
+        items.RemoveAt(lastIndex);
+        indexMap.Remove(item);
+    }
+
+    public void Insert(int index, T item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        items.Insert(index, item);
+
+        for (int i = index; i < items.Count; i++)
+            indexMap[items[i]] = i;
+    }
+
+    public void Clear()
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        items.Clear();
+        indexMap.Clear();
+    }
+
+    public bool Contains(T item) => indexMap.ContainsKey(item);
+    public int IndexOf(T item) => items.IndexOf(item);
+    public int BinarySearch(T item, IComparer<T>? comparer = null) => items.BinarySearch(item, comparer);
+
+    public void Sort(IComparer<T> comparer)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        items.Sort(comparer);
+
+        for (int i = 0; i < items.Count; i++)
+            indexMap[items[i]] = i;
+    }
+
+    public void CopyTo(T[] array, int arrayIndex) => items.CopyTo(array, arrayIndex);
+
+    public IEnumerator<T> GetEnumerator() => items.GetEnumerator();
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    public FastList() { }
+    public FastList(int count) { items.Capacity = count; }
+}

Engine.Core/Helpers/FastListOrdered.cs

@@ -0,0 +1,172 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+/// <summary>
+/// TODO This is VEERY experimental, and doesn't work well with the indices access. Use with caution
+/// </summary>
+/// <typeparam name="TIndex"></typeparam>
+/// <typeparam name="TItem"></typeparam>
+public class FastListOrdered<TIndex, TItem> : IList<TItem>, IReadOnlyList<TItem>, IEnumerable<TItem> where TItem : notnull where TIndex : IComparable
+{
+    private readonly SortedDictionary<TIndex, FastList<TItem>> items = null!;
+
+    private readonly Func<TItem, TIndex> getIndexFunc = null!;
+    private readonly IComparer<TIndex> sortBy = null!;
+
+    private int count = 0;
+    public int Count => count;
+
+    public bool IsReadOnly { get; set; } = false;
+
+    public TItem this[int index]
+    {
+        get { (TIndex tIndex, int i) = GetAt(index); return items[tIndex][i]; }
+        set
+        {
+            if (IsReadOnly)
+                throw new System.Data.ReadOnlyException();
+            (TIndex tIndex, int i) = GetAt(index); items[tIndex][i] = value;
+        }
+    }
+
+    private (TIndex TIndex, int i) GetAt(Index index)
+    {
+        int actualIndex = index.IsFromEnd
+                ? count - index.Value
+                : index.Value;
+
+        if (actualIndex < 0 || actualIndex >= count)
+            throw new IndexOutOfRangeException();
+
+        int leftIndex = actualIndex;
+        foreach ((TIndex i, FastList<TItem> list) in items)
+        {
+            if (leftIndex < list.Count)
+                return (i, leftIndex);
+            leftIndex -= list.Count;
+        }
+        throw new IndexOutOfRangeException();
+    }
+
+    public int IndexOf(TItem item)
+    {
+        int indexCounter = 0;
+        foreach ((TIndex index, FastList<TItem> list) in items)
+        {
+            int i = list.IndexOf(item);
+            if (i != -1)
+                return indexCounter + i;
+            indexCounter += list.Count;
+        }
+
+        return -1;
+    }
+
+    public void Add(TItem item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        TIndex key = getIndexFunc(item);
+        if (!items.TryGetValue(key, out FastList<TItem>? list))
+            items[key] = list = [];
+
+        list.Add(item);
+        count++;
+    }
+
+    public void Insert(int index, TItem item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        TIndex tIndex = getIndexFunc(item);
+        if (!items.TryGetValue(tIndex, out FastList<TItem>? list))
+            items[tIndex] = list = [];
+
+        list.Insert(index, item);
+        count++;
+    }
+
+    public bool Remove(TItem item)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        TIndex index = getIndexFunc(item);
+        if (!items.TryGetValue(index, out FastList<TItem>? list))
+            throw new Exceptions.NotFoundException($"Index of '{index}' is not found in the collector");
+
+        if (!list.Remove(item))
+            return false;
+
+        count--;
+        return true;
+    }
+
+    public void RemoveAt(int index)
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        (TIndex tIndex, int i) = GetAt(index);
+        items[tIndex].RemoveAt(i);
+        count--;
+    }
+
+    public void Clear()
+    {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
+        foreach ((TIndex index, FastList<TItem> list) in items)
+            list.Clear();
+
+        count = 0;
+    }
+
+    public bool Contains(TItem item)
+    {
+        foreach ((TIndex index, FastList<TItem> list) in items)
+            if (list.Contains(item))
+                return true;
+        return false;
+    }
+
+    public void CopyTo(TItem[] array, int arrayIndex)
+    {
+        int indexCounter = 0;
+
+        foreach ((TIndex index, FastList<TItem> list) in items)
+        {
+            list.CopyTo(array, indexCounter);
+            indexCounter += list.Count;
+        }
+    }
+
+    public IEnumerator<TItem> GetEnumerator()
+    {
+        foreach ((TIndex index, FastList<TItem> list) in items)
+            foreach (TItem item in list)
+                yield return item;
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    public FastListOrdered(Func<TItem, TIndex> getIndexFunc, Comparison<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = Comparer<TIndex>.Create(sortBy);
+        items = new(this.sortBy);
+    }
+
+    public FastListOrdered(Func<TItem, TIndex> getIndexFunc, IComparer<TIndex> sortBy)
+    {
+        this.getIndexFunc = getIndexFunc;
+        this.sortBy = sortBy;
+        items = new(sortBy);
+    }
+}

Engine.Core/Helpers/IPool.cs

@@ -0,0 +1,10 @@
+namespace Engine.Core;
+
+public interface IPool<T>
+{
+    Event<IPool<T>, T> OnRemoved { get; }
+    Event<IPool<T>, T> OnReturned { get; }
+
+    T Get();
+    void Return(T item);
+}

Engine.Core/Helpers/ListPool.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public class ListPool<T> : IPool<List<T>>
+{
+    public Event<IPool<List<T>>, List<T>> OnReturned { get; } = new();
+    public Event<IPool<List<T>>, List<T>> OnRemoved { get; } = new();
+
+    private readonly Func<List<T>> generator = null!;
+    private readonly Queue<List<T>> queue = new();
+
+    public List<T> Get()
+    {
+        if (!queue.TryDequeue(out List<T>? result))
+            result = generator();
+
+        result.Clear();
+        OnRemoved?.Invoke(this, result);
+        return result;
+    }
+
+    public void Return(List<T> list)
+    {
+        if (queue.Contains(list))
+            return;
+
+        list.Clear();
+        queue.Enqueue(list);
+        OnReturned?.Invoke(this, list);
+    }
+
+    public ListPool(int initialListCount = 1, int initialListCapacity = 32)
+    {
+        generator = () => new(initialListCapacity);
+        for (int i = 0; i < initialListCount; i++)
+            queue.Enqueue(generator());
+    }
+}

Engine.Core/Helpers/Pool.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+public class Pool<T> : IPool<T>
+{
+    public Event<IPool<T>, T> OnRemoved { get; } = new();
+    public Event<IPool<T>, T> OnReturned { get; } = new();
+
+    private readonly Func<T> generator = null!;
+    private readonly Queue<T> queue = new();
+    private readonly HashSet<T> queuedHashes = [];
+
+    public T Get()
+    {
+        if (!queue.TryDequeue(out T? result))
+            result = generator();
+
+        queuedHashes.Remove(result);
+        OnRemoved?.Invoke(this, result);
+        return result;
+    }
+
+    public void Return(T item)
+    {
+        if (queuedHashes.Contains(item))
+            return;
+
+        queue.Enqueue(item);
+        queuedHashes.Add(item);
+        OnReturned?.Invoke(this, item);
+    }
+
+    public Pool(Func<T> generator, int initialCapacity = 1)
+    {
+        this.generator = generator;
+        for (int i = 0; i < initialCapacity; i++)
+            queue.Enqueue(generator());
+    }
+}

Engine.Core/Helpers/Progression/IProgressionTracker.cs

@@ -0,0 +1,7 @@
+namespace Engine.Core;
+
+public interface IProgressionTracker : IReadOnlyProgressionTracker
+{
+    void Set(float progression, string status);
+    void Reset();
+}

Engine.Core/Helpers/Progression/IReadOnlyProgressionTracker.cs

@@ -0,0 +1,12 @@
+namespace Engine.Core;
+
+public interface IReadOnlyProgressionTracker
+{
+    Event<IReadOnlyProgressionTracker, ProgressionUpdatedArguments> OnUpdated { get; }
+    Event<IReadOnlyProgressionTracker> OnEnded { get; }
+
+    float Progression { get; }
+    string Status { get; }
+
+    readonly record struct ProgressionUpdatedArguments(float PreviousProgression, string PreviousStatus);
+}

Engine.Core/Helpers/Progression/ProgressionTracker.cs

@@ -0,0 +1,36 @@
+namespace Engine.Core;
+
+public class ProgressionTracker : IProgressionTracker
+{
+    public Event<IReadOnlyProgressionTracker, IReadOnlyProgressionTracker.ProgressionUpdatedArguments> OnUpdated { get; } = new();
+    public Event<IReadOnlyProgressionTracker> OnEnded { get; } = new();
+
+    public float Progression { get; private set; } = 0f;
+    public string Status { get; private set; } = "Default";
+
+    void IProgressionTracker.Set(float progression, string status)
+    {
+        if (Progression >= 1f)
+            return;
+
+        float previousProgression = Progression;
+        string previousStatus = Status;
+
+        Progression = progression.Clamp(Progression, 1f);
+        Status = status;
+
+        OnUpdated?.Invoke(this, new(previousProgression, previousStatus));
+
+        if (progression >= 1f)
+            OnEnded?.Invoke(this);
+    }
+
+    void IProgressionTracker.Reset()
+    {
+        Progression = 0f;
+        Status = "Default";
+
+        OnUpdated.Clear();
+        OnEnded.Clear();
+    }
+}

Engine.Core/Helpers/Progression/ProgressiveTask.cs

@@ -0,0 +1,9 @@
+using System.Threading.Tasks;
+
+namespace Engine.Core;
+
+public record struct ProgressiveTask<T>(IReadOnlyProgressionTracker ProgressionTracker, Task<T> Task)
+{
+    public static implicit operator (IReadOnlyProgressionTracker progressionTracker, Task<T> task)(ProgressiveTask<T> value) => (value.ProgressionTracker, value.Task);
+    public static implicit operator ProgressiveTask<T>((IReadOnlyProgressionTracker progressionTracker, Task<T> task) value) => new(value.progressionTracker, value.task);
+}

Engine.Core/HierarchyObject.cs

@@ -1,166 +0,0 @@
-using System.Collections;
-using System.Collections.Generic;
-
-using Syntriax.Engine.Core.Abstract;
-
-namespace Syntriax.Engine.Core;
-
-[System.Diagnostics.DebuggerDisplay("Name: {Name}, Initialized: {Initialized}")]
-public class HierarchyObject : BaseEntity, IHierarchyObject
-{
-    public event IHierarchyObject.EnteredHierarchyEventHandler? OnEnteredHierarchy = null;
-    public event IHierarchyObject.ExitedHierarchyEventHandler? OnExitedHierarchy = null;
-    public event IHierarchyObject.ParentChangedEventHandler? OnParentChanged = null;
-    public event IHierarchyObject.ChildrenAddedEventHandler? OnChildrenAdded = null;
-    public event IHierarchyObject.ChildrenRemovedEventHandler? OnChildrenRemoved = null;
-    public event IHasBehaviourController.BehaviourControllerAssignedEventHandler? OnBehaviourControllerAssigned = null;
-    public event INameable.NameChangedEventHandler? OnNameChanged = null;
-    public event IActive.ActiveChangedEventHandler? OnActiveChanged = null;
-
-    private string _name = nameof(HierarchyObject);
-    private IGameManager _gameManager = null!;
-    private IBehaviourController _behaviourController = null!;
-    private bool _isActive = false;
-    private readonly List<IHierarchyObject> _children = [];
-
-    public IHierarchyObject? Parent { get; private set; } = null;
-    public IReadOnlyList<IHierarchyObject> Children => _children;
-    public IBehaviourController BehaviourController => _behaviourController;
-    public IGameManager GameManager => _gameManager;
-    public bool IsInHierarchy => _gameManager is not null;
-    public bool IsActive => _isActive;
-
-    public string Name
-    {
-        get => _name;
-        set
-        {
-            if (value == _name) return;
-
-            string previousName = _name;
-            _name = value;
-            OnNameChanged?.Invoke(this, previousName);
-        }
-    }
-
-    protected virtual void OnEnteringHierarchy(IGameManager gameManager) { }
-    bool IHierarchyObject.EnterHierarchy(IGameManager gameManager)
-    {
-        if (IsInHierarchy)
-            return false;
-
-        _gameManager = gameManager;
-        UpdateActive();
-        OnEnteringHierarchy(gameManager);
-        OnEnteredHierarchy?.Invoke(this, gameManager);
-        return true;
-    }
-
-    protected virtual void OnExitingHierarchy(IGameManager gameManager) { }
-    bool IHierarchyObject.ExitHierarchy()
-    {
-        if (!IsInHierarchy || _gameManager is not IGameManager gameManager)
-            return false;
-
-        OnExitingHierarchy(gameManager);
-        _gameManager = null!;
-        SetParent(null);
-        OnExitedHierarchy?.Invoke(this, gameManager);
-        return true;
-    }
-
-    public void SetParent(IHierarchyObject? parent)
-    {
-        if (parent == this)
-            throw new Exceptions.AssignException($"{Name} can not parent itself");
-
-        if (Parent == parent)
-            return;
-
-        IHierarchyObject? previousParent = Parent;
-        if (previousParent is not null)
-        {
-            previousParent.RemoveChild(this);
-            previousParent.OnActiveChanged -= OnParentActiveChanged;
-        }
-
-        Parent = parent;
-
-        if (parent is not null)
-        {
-            if (parent.IsInHierarchy && !IsInHierarchy)
-                parent.GameManager.Register(this);
-
-            parent.AddChild(this);
-            parent.OnActiveChanged += OnParentActiveChanged;
-        }
-
-        UpdateActive();
-        OnParentChanged?.Invoke(this, previousParent, parent);
-    }
-
-    public void AddChild(IHierarchyObject parent)
-    {
-        if (_children.Contains(parent))
-            return;
-
-        _children.Add(parent);
-        parent.SetParent(this);
-        OnChildrenAdded?.Invoke(this, parent);
-    }
-
-    public void RemoveChild(IHierarchyObject parent)
-    {
-        if (!_children.Remove(parent))
-            return;
-
-        parent.SetParent(null);
-        OnChildrenRemoved?.Invoke(this, parent);
-    }
-
-    protected virtual void OnAssign(IBehaviourController behaviourController) { }
-    public bool Assign(IBehaviourController behaviourController)
-    {
-        if (IsInitialized)
-            return false;
-
-        _behaviourController = behaviourController;
-        OnAssign(behaviourController);
-        OnBehaviourControllerAssigned?.Invoke(this);
-        return true;
-    }
-
-    protected override void OnAssign(IStateEnable stateEnable)
-    {
-        base.OnAssign(stateEnable);
-
-        stateEnable.OnEnabledChanged += OnStateEnabledChanged;
-    }
-
-    private void OnParentActiveChanged(IActive sender, bool previousState) => UpdateActive();
-    private void OnStateEnabledChanged(IStateEnable sender, bool previousState) => UpdateActive();
-
-    private void UpdateActive()
-    {
-        bool previousActive = IsActive;
-        _isActive = StateEnable.Enabled && (Parent?.IsActive ?? true);
-
-        if (previousActive != IsActive)
-            OnActiveChanged?.Invoke(this, previousActive);
-    }
-
-    protected override void UnassignInternal()
-    {
-        base.UnassignInternal();
-        StateEnable.OnEnabledChanged -= OnStateEnabledChanged;
-    }
-
-    protected override void InitializeInternal()
-    {
-        base.InitializeInternal();
-        _behaviourController ??= Factory.BehaviourControllerFactory.Instantiate(this);
-    }
-
-    public IEnumerator<IHierarchyObject> GetEnumerator() => _children.GetEnumerator();
-    IEnumerator IEnumerable.GetEnumerator() => _children.GetEnumerator();
-}

Engine.Core/Math.cs

@@ -1,34 +1,92 @@
 using System;
 using System.Numerics;
 
-namespace Syntriax.Engine.Core;
+namespace Engine.Core;
 
 public static class Math
 {
     /// <summary>
-    /// The value of Pi (π), a mathematical constant approximately equal to 3.14159.
+    /// The value of Pi (π).
     /// </summary>
-    public const float PI = 3.1415926535897932f;
+    public const float Pi = 3.1415926535897932f;
 
     /// <summary>
-    /// The value of Tau (τ), a mathematical constant equal to 2π, approximately equal to 6.28319.
+    /// The value of Tau (τ), mathematical constant equal to 2π.
     /// </summary>
-    public const float Tau = 2f * PI;
+    public const float Tau = 2f * Pi;
 
     /// <summary>
-    /// The base of the natural logarithm, approximately equal to 2.71828.
+    /// The base of the natural logarithm.
     /// </summary>
     public const float E = 2.718281828459045f;
 
     /// <summary>
     /// The conversion factor from radians to degrees.
     /// </summary>
-    public const float RadianToDegree = 180f / PI;
+    public const float RadianToDegree = 180f / Pi;
 
     /// <summary>
     /// The conversion factor from degrees to radians.
     /// </summary>
-    public const float DegreeToRadian = PI / 180f;
+    public const float DegreeToRadian = Pi / 180f;
+
+    /// <summary>
+    /// Gets one minus of given <see cref="T"/>.
+    /// </summary>
+    /// <param name="value">The value <see cref="T"/>.</param>
+    /// <returns>One minus of given <see cref="T"/>.</returns>
+    public static T OneMinus<T>(T value) where T : INumber<T> => T.One - value;
+
+    /// <summary>
+    /// Adds two <see cref="T"/>s.
+    /// </summary>
+    /// <param name="left">The first <see cref="T"/>.</param>
+    /// <param name="value">The second <see cref="T"/>.</param>
+    /// <returns>The sum of the two <see cref="T"/>s.</returns>
+    public static T Add<T>(T left, T value) where T : INumber<T> => left + value;
+
+    /// <summary>
+    /// Subtracts one <see cref="T"/> from another.
+    /// </summary>
+    /// <param name="left">The <see cref="T"/> to subtract from.</param>
+    /// <param name="value">The <see cref="T"/> to subtract.</param>
+    /// <returns>The result of subtracting the second <see cref="T"/> from the first.</returns>
+    public static T Subtract<T>(T left, T value) where T : INumber<T> => left - value;
+
+    /// <summary>
+    /// Multiplies a <see cref="T"/> by a scalar value.
+    /// </summary>
+    /// <param name="left">The <see cref="T"/>.</param>
+    /// <param name="multiplier">The scalar value.</param>
+    /// <returns>The result of multiplying the <see cref="T"/> by the scalar value.</returns>
+    public static T Multiply<T>(T left, T multiplier) where T : INumber<T> => left * multiplier;
+
+    /// <summary>
+    /// Divides a <see cref="T"/> by a scalar value.
+    /// </summary>
+    /// <param name="left">The <see cref="T"/>.</param>
+    /// <param name="divider">The scalar value.</param>
+    /// <returns>The result of dividing the <see cref="T"/> by the scalar value.</returns>
+    public static T Divide<T>(T left, T divider) where T : INumber<T> => left / divider;
+
+    /// <summary>
+    /// Returns the true mathematical modulus of a <see cref="T"/> value. 
+    /// Unlike the remainder operator (%), this result is always non-negative,
+    /// even when the <paramref name="value"/> operand is negative.
+    /// </summary>
+    /// <typeparam name="T">A numeric type that implements <see cref="INumber{T}"/>.</typeparam>
+    /// <param name="value">The dividend <see cref="T"/> value.</param>
+    /// <param name="modulus">The modulus <see cref="T"/> value (must be non-zero).</param>
+    /// <returns>
+    /// The non-negative remainder of <paramref name="value"/> divided by <paramref name="modulus"/>.
+    /// </returns>
+    public static T Mod<T>(T value, T modulus) where T : INumber<T>
+    {
+        T result = value % modulus;
+        if (result < T.Zero)
+            result += modulus;
+        return result;
+    }
 
     /// <summary>
     /// Returns the absolute value of a number.
@@ -52,6 +110,13 @@ public static class Math
     /// <returns>The sine of <paramref name="x"/>.</returns>
     public static float Sin(float x) => MathF.Sin(x);
 
+    /// <summary>
+    /// Returns the tangent of a number.
+    /// </summary>
+    /// <param name="x">The angle, in radians.</param>
+    /// <returns>The tangent of <paramref name="x"/>.</returns>
+    public static float Tan(float x) => MathF.Tan(x);
+
     /// <summary>
     /// Returns the arccosine of a number.
     /// </summary>
@@ -66,6 +131,13 @@ public static class Math
     /// <returns>The arcsine of <paramref name="x"/>.</returns>
     public static float Asin(float x) => MathF.Asin(x);
 
+    /// <summary>
+    /// Returns the angle whose tangent is the specified number.
+    /// </summary>
+    /// <param name="x">The tangent value.</param>
+    /// <returns>The angle, in radians.</returns>
+    public static float Atan(float x) => MathF.Atan(x);
+
     /// <summary>
     /// Returns the angle whose tangent is the quotient of two specified numbers.
     /// </summary>
@@ -182,13 +254,34 @@ public static class Math
     public static T Lerp<T>(T x, T y, T t) where T : IFloatingPoint<T> => x + (y - x) * t;
 
     /// <summary>
-    /// Rounds a number to a specified number of fractional digits.
+    /// Rounds a number to the closest integer.
     /// </summary>
     /// <param name="x">The number to round.</param>
-    /// <param name="digits">The number of fractional digits in the return value.</param>
+    /// <param name="roundMode">Specification for how to round <paramref name="x"/> if it is midway between two other numbers.</param>
-    /// <param name="mode">Specification for how to round <paramref name="x"/> if it is midway between two other numbers.</param>
+    /// <returns>The number <paramref name="x"/> rounded to the closest integer.</returns>
-    /// <returns>The number <paramref name="x"/> rounded to <paramref name="digits"/> fractional digits.</returns>
+    public static float Round(float x, RoundMode roundMode) => RoundToInt(x, roundMode);
-    public static float Round(float x, int digits, MidpointRounding mode) => MathF.Round(x, digits, mode);
+
+    /// <summary>
+    /// Rounds a number to the closest integer.
+    /// </summary>
+    /// <param name="x">The number to round.</param>
+    /// <param name="roundMode">Specification for how to round <paramref name="x"/> if it's midway between two numbers</param>
+    /// <returns>The number <paramref name="x"/> rounded to the closest integer.</returns>
+    public static int RoundToInt(float x, RoundMode roundMode = RoundMode.Ceil)
+    {
+        float remainder = x.Mod(1f);
+
+        if (remainder == .5f)
+            if (roundMode == RoundMode.Floor)
+                return (int)x;
+            else
+                return (int)(x + .5f);
+
+        if (x < 0f)
+            return (int)(x - .5f);
+        return (int)(x + .5f);
+    }
+    public enum RoundMode { Ceil, Floor };
 
     /// <summary>
     /// Returns the square of a number.

Engine.Core/MathExtensions.cs

@@ -1,10 +1,28 @@
 using System;
 using System.Numerics;
 
-namespace Syntriax.Engine.Core;
+namespace Engine.Core;
 
 public static class MathExtensions
 {
+    /// <inheritdoc cref="Math.OneMinus{T}(T)" />
+    public static T OneMinus<T>(this T value) where T : INumber<T> => Math.OneMinus(value);
+
+    /// <inheritdoc cref="Math.Add{T}(T, T)" />
+    public static T Add<T>(this T left, T value) where T : INumber<T> => Math.Add(left, value);
+
+    /// <inheritdoc cref="Math.Subtract{T}(T, T)" />
+    public static T Subtract<T>(this T left, T value) where T : INumber<T> => Math.Subtract(left, value);
+
+    /// <inheritdoc cref="Math.Multiply{T}(T, T)" />
+    public static T Multiply<T>(this T left, T multiplier) where T : INumber<T> => Math.Multiply(left, multiplier);
+
+    /// <inheritdoc cref="Math.Divide{T}(T, T)" />
+    public static T Divide<T>(this T left, T divider) where T : INumber<T> => Math.Divide(left, divider);
+
+    /// <inheritdoc cref="Math.Mod{T}(T, T)" />
+    public static T Mod<T>(this T value, T modulus) where T : INumber<T> => Math.Mod(value, modulus);
+
     /// <inheritdoc cref="Math.Abs{T}(T)" />
     public static T Abs<T>(this T x) where T : INumber<T> => Math.Abs(x);
 
@@ -14,12 +32,18 @@ public static class MathExtensions
     /// <inheritdoc cref="Math.Sin(float)" />
     public static float Sin(this float x) => Math.Sin(x);
 
+    /// <inheritdoc cref="Math.Tan(float)" />
+    public static float Tan(this float x) => Math.Tan(x);
+
     /// <inheritdoc cref="Math.Acos(float)" />
     public static float Acos(this float x) => Math.Acos(x);
 
     /// <inheritdoc cref="Math.Asin(float)" />
     public static float Asin(this float x) => Math.Asin(x);
 
+    /// <inheritdoc cref="Math.Atan(float)" />
+    public static float Atan(this float x) => Math.Atan(x);
+
     /// <inheritdoc cref="Math.Atan2(float, float)" />
     public static float Atan2(this float y, float x) => Math.Atan2(y, x);
 
@@ -63,7 +87,10 @@ public static class MathExtensions
     public static T Lerp<T>(this T x, T y, T t) where T : IFloatingPoint<T> => Math.Lerp(x, y, t);
 
     /// <inheritdoc cref="Math.Round(float, int, MidpointRounding)" />
-    public static float Round(this float x, int digits, MidpointRounding mode) => Math.Round(x, digits, mode);
+    public static float Round(this float x, Math.RoundMode mode) => Math.Round(x, mode);
+
+    /// <inheritdoc cref="Math.RoundToInt(float, Math.RoundMode)" />
+    public static int RoundToInt(this float x, Math.RoundMode roundMode = Math.RoundMode.Ceil) => Math.RoundToInt(x, roundMode);
 
     /// <inheritdoc cref="Math.Sqr{T}(T)" />
     public static T Sqr<T>(this T x) where T : INumber<T> => Math.Sqr(x);

Engine.Core/Preserver.cs

@@ -0,0 +1,10 @@
+namespace Engine.Core
+{
+    // This is pretty much so the assembly gets loaded automatically because 
+    // the builds include the assembly but sometimes doesn't link load it at startup.
+    // I will hopefully one day fix it and remove this. 
+    public static class Preserver
+    {
+        public static void Preserve() { }
+    }
+}

Engine.Core/Primitives/AABB.cs

@@ -1,93 +0,0 @@
-using System.Collections.Generic;
-
-namespace Syntriax.Engine.Core;
-
-/// <summary>
-/// Represents an Axis-Aligned Bounding Box (AABB) in 2D space.
-/// </summary>
-/// <param name="lowerBoundary">The lower boundary of the <see cref="AABB"/>.</param>
-/// <param name="upperBoundary">The upper boundary of the <see cref="AABB"/>.</param>
-/// <remarks>
-/// Initializes a new instance of the <see cref="AABB"/> struct with the specified lower and upper boundaries.
-/// </remarks>
-[System.Diagnostics.DebuggerDisplay("LowerBoundary: {LowerBoundary.ToString(), nq}, UpperBoundary: {UpperBoundary.ToString(), nq}")]
-public readonly struct AABB(Vector2D lowerBoundary, Vector2D upperBoundary)
-{
-    /// <summary>
-    /// The lower boundary of the <see cref="AABB"/>.
-    /// </summary>
-    public readonly Vector2D LowerBoundary = lowerBoundary;
-
-    /// <summary>
-    /// The upper boundary of the <see cref="AABB"/>.
-    /// </summary>
-    public readonly Vector2D UpperBoundary = upperBoundary;
-
-    /// <summary>
-    /// Gets the center point of the <see cref="AABB"/>.
-    /// </summary>
-    public readonly Vector2D Center => (LowerBoundary + UpperBoundary) * .5f;
-
-    /// <summary>
-    /// Gets the size of the <see cref="AABB"/>.
-    /// </summary>
-    public readonly Vector2D Size => LowerBoundary.FromTo(UpperBoundary).Abs();
-
-    /// <summary>
-    /// Gets half the size of the <see cref="AABB"/>.
-    /// </summary>
-    public readonly Vector2D SizeHalf => Size * .5f;
-
-    /// <summary>
-    /// Creates an <see cref="AABB"/> from a collection of <see cref="Vector2D"/>s.
-    /// </summary>
-    /// <param name="vectors">The collection of <see cref="Vector2D"/>s.</param>
-    /// <returns>An <see cref="AABB"/> that bounds all the <see cref="Vector2D"/>s.</returns>
-    public static AABB FromVectors(IEnumerable<Vector2D> vectors)
-    {
-        int counter = 0;
-
-        Vector2D lowerBoundary = new(float.MaxValue, float.MaxValue);
-        Vector2D upperBoundary = new(float.MinValue, float.MinValue);
-
-        foreach (Vector2D vector in vectors)
-        {
-            lowerBoundary = Vector2D.Min(lowerBoundary, vector);
-            upperBoundary = Vector2D.Max(upperBoundary, vector);
-            counter++;
-        }
-
-        if (counter < 2)
-            throw new System.ArgumentException($"Parameter {nameof(vectors)} must have at least 2 items.");
-
-        return new(lowerBoundary, upperBoundary);
-    }
-
-    /// <summary>
-    /// Converts the <see cref="AABB"/> to its string representation.
-    /// </summary>
-    /// <returns>A string representation of the <see cref="AABB"/>.</returns>
-    public override string ToString() => $"{nameof(AABB)}({LowerBoundary}, {UpperBoundary})";
-
-    /// <summary>
-    /// Checks if two <see cref="AABB"/>s are approximately equal.
-    /// </summary>
-    /// <param name="left">The first <see cref="AABB"/>.</param>
-    /// <param name="right">The second <see cref="AABB"/>.</param>
-    /// <param name="epsilon">The epsilon range.</param>
-    /// <returns><see cref="true"/> if the <see cref="AABB"/>s are approximately equal; otherwise, <see cref="false"/>.</returns>
-    public static bool ApproximatelyEquals(AABB left, AABB right, float epsilon = float.Epsilon)
-        => left.LowerBoundary.ApproximatelyEquals(right.LowerBoundary, epsilon) && left.UpperBoundary.ApproximatelyEquals(right.UpperBoundary, epsilon);
-}
-
-/// <summary>
-/// Provides extension methods for the <see cref="AABB"/> struct.
-/// </summary>
-public static class AABBExtensions
-{
-    /// <inheritdoc cref="AABB.ToAABB" />
-    public static AABB ToAABB(this IEnumerable<Vector2D> vectors) => AABB.FromVectors(vectors);
-
-    /// <inheritdoc cref="AABB.ApproximatelyEquals" />
-    public static bool ApproximatelyEquals(this AABB left, AABB right, float epsilon = float.Epsilon) => AABB.ApproximatelyEquals(left, right, epsilon);
-}

Engine.Core/Primitives/AABB2D.cs

@@ -0,0 +1,114 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+/// <summary>
+/// Represents an Axis-Aligned Bounding Box (AABB) in 2D space.
+/// </summary>
+/// <param name="lowerBoundary">The lower boundary of the <see cref="AABB2D"/>.</param>
+/// <param name="upperBoundary">The upper boundary of the <see cref="AABB2D"/>.</param>
+/// <remarks>
+/// Initializes a new instance of the <see cref="AABB2D"/> struct with the specified lower and upper boundaries.
+/// </remarks>
+[System.Diagnostics.DebuggerDisplay("LowerBoundary: {LowerBoundary.ToString(), nq}, UpperBoundary: {UpperBoundary.ToString(), nq}")]
+public readonly struct AABB2D(Vector2D lowerBoundary, Vector2D upperBoundary) : IEquatable<AABB2D>
+{
+    /// <summary>
+    /// The lower boundary of the <see cref="AABB2D"/>.
+    /// </summary>
+    public readonly Vector2D LowerBoundary = lowerBoundary;
+
+    /// <summary>
+    /// The upper boundary of the <see cref="AABB2D"/>.
+    /// </summary>
+    public readonly Vector2D UpperBoundary = upperBoundary;
+
+    /// <summary>
+    /// Gets the center point of the <see cref="AABB2D"/>.
+    /// </summary>
+    public readonly Vector2D Center => (LowerBoundary + UpperBoundary) * .5f;
+
+    /// <summary>
+    /// Gets the size of the <see cref="AABB2D"/>.
+    /// </summary>
+    public readonly Vector2D Size => LowerBoundary.FromTo(UpperBoundary).Abs();
+
+    /// <summary>
+    /// Gets half the size of the <see cref="AABB2D"/>.
+    /// </summary>
+    public readonly Vector2D SizeHalf => Size * .5f;
+
+    public static bool operator ==(AABB2D left, AABB2D right) => left.UpperBoundary == right.UpperBoundary && left.LowerBoundary == right.LowerBoundary;
+    public static bool operator !=(AABB2D left, AABB2D right) => left.UpperBoundary != right.UpperBoundary || left.LowerBoundary != right.LowerBoundary;
+
+    public static implicit operator AABB2D(Circle circle) => new(circle.Center - new Vector2D(circle.Radius, circle.Radius), circle.Center + new Vector2D(circle.Radius, circle.Radius));
+    public static implicit operator AABB2D(Shape2D shape) => FromVectors(shape.Vertices);
+
+    /// <summary>
+    /// Creates an <see cref="AABB2D"/> from a collection of <see cref="Vector2D"/>s.
+    /// </summary>
+    /// <param name="vectors">The collection of <see cref="Vector2D"/>s.</param>
+    /// <returns>An <see cref="AABB2D"/> that bounds all the <see cref="Vector2D"/>s.</returns>
+    public static AABB2D FromVectors(IEnumerable<Vector2D> vectors)
+    {
+        int counter = 0;
+
+        Vector2D lowerBoundary = new(float.MaxValue, float.MaxValue);
+        Vector2D upperBoundary = new(float.MinValue, float.MinValue);
+
+        foreach (Vector2D vector in vectors)
+        {
+            lowerBoundary = Vector2D.Min(lowerBoundary, vector);
+            upperBoundary = Vector2D.Max(upperBoundary, vector);
+            counter++;
+        }
+
+        if (counter < 2)
+            throw new ArgumentException($"Parameter {nameof(vectors)} must have at least 2 items.");
+
+        return new(lowerBoundary, upperBoundary);
+    }
+
+    /// <summary>
+    /// Checks if two <see cref="AABB2D"/>s are approximately equal.
+    /// </summary>
+    /// <param name="left">The first <see cref="AABB2D"/>.</param>
+    /// <param name="right">The second <see cref="AABB2D"/>.</param>
+    /// <param name="epsilon">The epsilon range.</param>
+    /// <returns><see cref="true"/> if the <see cref="AABB2D"/>s are approximately equal; otherwise, <see cref="false"/>.</returns>
+    public static bool ApproximatelyEquals(AABB2D left, AABB2D right, float epsilon = float.Epsilon)
+        => left.LowerBoundary.ApproximatelyEquals(right.LowerBoundary, epsilon) && left.UpperBoundary.ApproximatelyEquals(right.UpperBoundary, epsilon);
+
+    /// <summary>
+    /// Determines whether the specified object is equal to the current <see cref="AABB2D"/>.
+    /// </summary>
+    /// <param name="obj">The object to compare with the current <see cref="AABB2D"/>.</param>
+    /// <returns><see cref="true"/> if the specified object is equal to the current <see cref="AABB2D"/>; otherwise, <see cref="false"/>.</returns>
+    public override bool Equals(object? obj) => obj is AABB2D aabb && this == aabb;
+    public bool Equals(AABB2D other) => this == other;
+
+    /// <summary>
+    /// Generates a hash code for the <see cref="AABB2D"/>.
+    /// </summary>
+    /// <returns>A hash code for the <see cref="AABB2D"/>.</returns>
+    public override int GetHashCode() => System.HashCode.Combine(LowerBoundary, UpperBoundary);
+
+    /// <summary>
+    /// Converts the <see cref="AABB2D"/> to its string representation.
+    /// </summary>
+    /// <returns>A string representation of the <see cref="AABB2D"/>.</returns>
+    public override string ToString() => $"{nameof(AABB2D)}({LowerBoundary}, {UpperBoundary})";
+}
+
+/// <summary>
+/// Provides extension methods for the <see cref="AABB2D"/> struct.
+/// </summary>
+public static class AABBExtensions
+{
+    /// <inheritdoc cref="AABB2D.FromVectors" />
+    public static AABB2D ToAABB(this IEnumerable<Vector2D> vectors) => AABB2D.FromVectors(vectors);
+
+    /// <inheritdoc cref="AABB2D.ApproximatelyEquals" />
+    public static bool ApproximatelyEquals(this AABB2D left, AABB2D right, float epsilon = float.Epsilon) => AABB2D.ApproximatelyEquals(left, right, epsilon);
+}

Engine.Core/Primitives/AABB3D.cs

@@ -0,0 +1,113 @@
+using System;
+using System.Collections.Generic;
+
+namespace Engine.Core;
+
+/// <summary>
+/// Represents an Axis-Aligned Bounding Box (AABB) in 3D space.
+/// </summary>
+/// <param name="lowerBoundary">The lower boundary of the <see cref="AABB3D"/>.</param>
+/// <param name="upperBoundary">The upper boundary of the <see cref="AABB3D"/>.</param>
+/// <remarks>
+/// Initializes a new instance of the <see cref="AABB3D"/> struct with the specified lower and upper boundaries.
+/// </remarks>
+[System.Diagnostics.DebuggerDisplay("LowerBoundary: {LowerBoundary.ToString(), nq}, UpperBoundary: {UpperBoundary.ToString(), nq}")]
+public readonly struct AABB3D(Vector3D lowerBoundary, Vector3D upperBoundary) : IEquatable<AABB3D>
+{
+    /// <summary>
+    /// The lower boundary of the <see cref="AABB3D"/>.
+    /// </summary>
+    public readonly Vector3D LowerBoundary = lowerBoundary;
+
+    /// <summary>
+    /// The upper boundary of the <see cref="AABB3D"/>.
+    /// </summary>
+    public readonly Vector3D UpperBoundary = upperBoundary;
+
+    /// <summary>
+    /// Gets the center point of the <see cref="AABB3D"/>.
+    /// </summary>
+    public readonly Vector3D Center => (LowerBoundary + UpperBoundary) * .5f;
+
+    /// <summary>
+    /// Gets the size of the <see cref="AABB3D"/>.
+    /// </summary>
+    public readonly Vector3D Size => LowerBoundary.FromTo(UpperBoundary).Abs();
+
+    /// <summary>
+    /// Gets half the size of the <see cref="AABB3D"/>.
+    /// </summary>
+    public readonly Vector3D SizeHalf => Size * .5f;
+
+    public static bool operator ==(AABB3D left, AABB3D right) => left.UpperBoundary == right.UpperBoundary && left.LowerBoundary == right.LowerBoundary;
+    public static bool operator !=(AABB3D left, AABB3D right) => left.UpperBoundary != right.UpperBoundary || left.LowerBoundary != right.LowerBoundary;
+
+    public static implicit operator AABB3D(Sphere3D sphere) => new(sphere.Center - new Vector3D(sphere.Radius, sphere.Radius, sphere.Radius), sphere.Center + new Vector3D(sphere.Radius, sphere.Radius, sphere.Radius));
+
+    /// <summary>
+    /// Creates an <see cref="AABB3D"/> from a collection of <see cref="Vector3D"/>s.
+    /// </summary>
+    /// <param name="vectors">The collection of <see cref="Vector3D"/>s.</param>
+    /// <returns>An <see cref="AABB3D"/> that bounds all the <see cref="Vector3D"/>s.</returns>
+    public static AABB3D FromVectors(IEnumerable<Vector3D> vectors)
+    {
+        int counter = 0;
+
+        Vector3D lowerBoundary = new(float.MaxValue, float.MaxValue, float.MaxValue);
+        Vector3D upperBoundary = new(float.MinValue, float.MinValue, float.MinValue);
+
+        foreach (Vector3D vector in vectors)
+        {
+            lowerBoundary = Vector3D.Min(lowerBoundary, vector);
+            upperBoundary = Vector3D.Max(upperBoundary, vector);
+            counter++;
+        }
+
+        if (counter < 2)
+            throw new ArgumentException($"Parameter {nameof(vectors)} must have at least 2 items.");
+
+        return new(lowerBoundary, upperBoundary);
+    }
+
+    /// <summary>
+    /// Checks if two <see cref="AABB3D"/>s are approximately equal.
+    /// </summary>
+    /// <param name="left">The first <see cref="AABB3D"/>.</param>
+    /// <param name="right">The second <see cref="AABB3D"/>.</param>
+    /// <param name="epsilon">The epsilon range.</param>
+    /// <returns><see cref="true"/> if the <see cref="AABB3D"/>s are approximately equal; otherwise, <see cref="false"/>.</returns>
+    public static bool ApproximatelyEquals(AABB3D left, AABB3D right, float epsilon = float.Epsilon)
+        => left.LowerBoundary.ApproximatelyEquals(right.LowerBoundary, epsilon) && left.UpperBoundary.ApproximatelyEquals(right.UpperBoundary, epsilon);
+
+    /// <summary>
+    /// Determines whether the specified object is equal to the current <see cref="AABB3D"/>.
+    /// </summary>
+    /// <param name="obj">The object to compare with the current <see cref="AABB3D"/>.</param>
+    /// <returns><see cref="true"/> if the specified object is equal to the current <see cref="AABB3D"/>; otherwise, <see cref="false"/>.</returns>
+    public override bool Equals(object? obj) => obj is AABB3D aabb && this == aabb;
+    public bool Equals(AABB3D other) => this == other;
+
+    /// <summary>
+    /// Generates a hash code for the <see cref="AABB3D"/>.
+    /// </summary>
+    /// <returns>A hash code for the <see cref="AABB3D"/>.</returns>
+    public override int GetHashCode() => System.HashCode.Combine(LowerBoundary, UpperBoundary);
+
+    /// <summary>
+    /// Converts the <see cref="AABB3D"/> to its string representation.
+    /// </summary>
+    /// <returns>A string representation of the <see cref="AABB3D"/>.</returns>
+    public override string ToString() => $"{nameof(AABB3D)}({LowerBoundary}, {UpperBoundary})";
+}
+
+/// <summary>
+/// Provides extension methods for the <see cref="AABB3D"/> struct.
+/// </summary>
+public static class AABB3DExtensions
+{
+    /// <inheritdoc cref="AABB3D.FromVectors" />
+    public static AABB3D ToAABB3D(this IEnumerable<Vector3D> vectors) => AABB3D.FromVectors(vectors);
+
+    /// <inheritdoc cref="AABB3D.ApproximatelyEquals" />
+    public static bool ApproximatelyEquals(this AABB3D left, AABB3D right, float epsilon = float.Epsilon) => AABB3D.ApproximatelyEquals(left, right, epsilon);
+}