docs: added documentation to draw & update interfaces

Engine.Core/Abstract/IBehaviourController.cs

@@ -3,25 +3,10 @@ using System.Collections.Generic;
 namespace Syntriax.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="IUniverseObject"/>.
+/// Represents a controller for managing <see cref="IBehaviour"/>s. Connected to an <see cref="IUniverseObject"/>.
 /// </summary>
 public interface IBehaviourController : IEntity, IHasUniverseObject, IEnumerable<IBehaviour>
 {
-    /// <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>
@@ -83,20 +68,6 @@ public interface IBehaviourController : IEntity, IHasUniverseObject, IEnumerable
     /// <param name="behaviour">The <see cref="IBehaviour"/> to remove.</param>
     void RemoveBehaviour<T>(T behaviour) where T : class, IBehaviour;
 
-    /// <summary>
-    /// 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);
-
 }

Engine.Core/Abstract/IUniverse.cs

@@ -18,9 +18,24 @@ public interface IUniverse : IEntity, IEnumerable<IUniverseObject>
     event UpdateEventHandler? OnUpdate;
 
     /// <summary>
-    /// Event triggered when <see cref="PreDraw"/> is called on the <see cref="IUniverse"/>.
+    /// Event triggered after <see cref="Update(UniverseTime)"/> is called on the <see cref="IUniverse"/>.
     /// </summary>
-    event PreDrawEventHandler? OnPreDraw;
+    event UpdateEventHandler? OnPostUpdate;
+
+    /// <summary>
+    /// Event triggered when <see cref="Draw"/> is about to be called called on the <see cref="IUniverse"/>.
+    /// </summary>
+    event DrawEventHandler? OnPreDraw;
+
+    /// <summary>
+    /// Event triggered when <see cref="Draw"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    event DrawEventHandler? OnDraw;
+
+    /// <summary>
+    /// Event triggered after <see cref="Draw"/> is called on the <see cref="IUniverse"/>.
+    /// </summary>
+    event DrawEventHandler? OnPostDraw;
 
     /// <summary>
     /// Event triggered when a <see cref="IUniverseObject"/> is registered to the <see cref="IUniverse"/>.
@@ -84,14 +99,14 @@ public interface IUniverse : IEntity, IEnumerable<IUniverseObject>
     void Update(UniverseTime universeTime);
 
     /// <summary>
-    /// Performs operations that should be done before the draw calls.
+    /// Performs operations that should be done to the draw.
     /// </summary>
-    void PreDraw();
+    void Draw();
 
     delegate void TimeScaleChangedEventHandler(IUniverse sender, float previousTimeScale);
 
     delegate void UpdateEventHandler(IUniverse sender, UniverseTime engineTime);
-    delegate void PreDrawEventHandler(IUniverse sender);
+    delegate void DrawEventHandler(IUniverse sender);
 
     delegate void UniverseObjectRegisteredEventHandler(IUniverse sender, IUniverseObject universeObjectRegistered);
     delegate void UniverseObjectUnRegisteredEventHandler(IUniverse sender, IUniverseObject universeObjectUnregistered);

Engine.Core/Behaviour.cs

@@ -1,9 +1,9 @@
 namespace Syntriax.Engine.Core;
 
-public abstract class Behaviour : BehaviourBase
+public abstract class Behaviour : BehaviourBase, IFirstFrameUpdate,
+    IPreUpdate, IUpdate, IPostUpdate,
+    IPreDraw, IDraw, IPostDraw
 {
-    private bool isInitializedThisFrame = false;
-
     protected IUniverse Universe => BehaviourController.UniverseObject.Universe;
     protected IUniverseObject UniverseObject => BehaviourController.UniverseObject;
 
@@ -20,11 +20,6 @@ public abstract class Behaviour : BehaviourBase
     protected virtual void OnInitialize() { }
     protected virtual void OnInitialize(IInitializable _)
     {
-        isInitializedThisFrame = true;
-
-        BehaviourController.OnPreUpdate += PreUpdate;
-        BehaviourController.OnPreDraw += PreDraw;
-        BehaviourController.OnUpdate += Update;
         BehaviourController.UniverseObject.OnEnteredUniverse += EnteredUniverse;
         BehaviourController.UniverseObject.OnExitedUniverse += ExitedUniverse;
 
@@ -37,9 +32,6 @@ public abstract class Behaviour : BehaviourBase
     protected virtual void OnFinalize() { }
     protected virtual void OnFinalize(IInitializable _)
     {
-        BehaviourController.OnPreUpdate -= PreUpdate;
-        BehaviourController.OnPreDraw -= PreDraw;
-        BehaviourController.OnUpdate -= Update;
         BehaviourController.UniverseObject.OnEnteredUniverse -= EnteredUniverse;
         BehaviourController.UniverseObject.OnExitedUniverse -= ExitedUniverse;
 
@@ -49,9 +41,16 @@ public abstract class Behaviour : BehaviourBase
             ExitedUniverse(UniverseObject, Universe);
     }
 
+    protected virtual void OnFirstActiveFrame() { }
+    void IFirstFrameUpdate.FirstActiveFrame()
+    {
+        Debug.Assert.AssertInitialized(this);
+        OnFirstActiveFrame();
+    }
+
     protected virtual void OnPreUpdatePreActiveCheck() { }
     protected virtual void OnPreUpdate() { }
-    protected virtual void PreUpdate(IBehaviourController _)
+    void IPreUpdate.PreUpdate()
     {
         Debug.Assert.AssertInitialized(this);
 
@@ -60,22 +59,12 @@ public abstract class Behaviour : BehaviourBase
         if (!IsActive)
             return;
 
-        if (isInitializedThisFrame)
-            FirstActiveFrame();
-
         OnPreUpdate();
     }
 
-    protected virtual void OnFirstActiveFrame() { }
-    protected virtual void FirstActiveFrame()
-    {
-        OnFirstActiveFrame();
-        isInitializedThisFrame = false;
-    }
-
     protected virtual void OnUpdatePreActiveCheck() { }
     protected virtual void OnUpdate() { }
-    protected virtual void Update(IBehaviourController _)
+    void IUpdate.Update()
     {
         Debug.Assert.AssertInitialized(this);
 
@@ -87,9 +76,23 @@ public abstract class Behaviour : BehaviourBase
         OnUpdate();
     }
 
+    protected virtual void OnPostUpdatePreActiveCheck() { }
+    protected virtual void OnPostUpdate() { }
+    void IPostUpdate.PostUpdate()
+    {
+        Debug.Assert.AssertInitialized(this);
+
+        OnPostUpdatePreActiveCheck();
+
+        if (!StateEnable.Enabled)
+            return;
+
+        OnPostUpdate();
+    }
+
     protected virtual void OnPreDrawPreActiveCheck() { }
     protected virtual void OnPreDraw() { }
-    protected virtual void PreDraw(IBehaviourController _)
+    void IPreDraw.PreDraw()
     {
         Debug.Assert.AssertInitialized(this);
 
@@ -101,6 +104,34 @@ public abstract class Behaviour : BehaviourBase
         OnPreDraw();
     }
 
+    protected virtual void OnDrawPreActiveCheck() { }
+    protected virtual void OnDraw() { }
+    void IDraw.Draw()
+    {
+        Debug.Assert.AssertInitialized(this);
+
+        OnDrawPreActiveCheck();
+
+        if (!StateEnable.Enabled)
+            return;
+
+        OnDraw();
+    }
+
+    protected virtual void OnPostDrawPreActiveCheck() { }
+    protected virtual void OnPostDraw() { }
+    void IPostDraw.PostDraw()
+    {
+        Debug.Assert.AssertInitialized(this);
+
+        OnPostDrawPreActiveCheck();
+
+        if (!StateEnable.Enabled)
+            return;
+
+        OnPostDraw();
+    }
+
     protected virtual void OnEnteredUniverse(IUniverse universe) { }
     protected virtual void EnteredUniverse(IUniverseObject sender, IUniverse universe) => OnEnteredUniverse(universe);
 

Engine.Core/Behaviour2D.cs

@@ -17,10 +17,6 @@ public abstract class Behaviour2D : Behaviour, IBehaviour2D
     }
 
     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 EnteredUniverse(IUniverseObject sender, IUniverse universe) => base.EnteredUniverse(sender, universe);
     protected sealed override void ExitedUniverse(IUniverseObject sender, IUniverse universe) => base.ExitedUniverse(sender, universe);
 }

Engine.Core/BehaviourController.cs

@@ -8,10 +8,6 @@ namespace Syntriax.Engine.Core;
 [System.Diagnostics.DebuggerDisplay("Behaviour Count: {behaviours.Count}")]
 public class BehaviourController : BaseEntity, IBehaviourController
 {
-    public event IBehaviourController.PreUpdateEventHandler? OnPreUpdate = null;
-    public event IBehaviourController.UpdateEventHandler? OnUpdate = null;
-    public event IBehaviourController.PreDrawEventHandler? OnPreDraw = null;
-
     public event IBehaviourController.BehaviourAddedEventHandler? OnBehaviourAdded = null;
     public event IBehaviourController.BehaviourRemovedEventHandler? OnBehaviourRemoved = null;
     public event IHasUniverseObject.UniverseObjectAssignedEventHandler? OnUniverseObjectAssigned = null;
@@ -36,7 +32,10 @@ public class BehaviourController : BaseEntity, IBehaviourController
     }
 
     public T AddBehaviour<T>(params object?[]? args) where T : class, IBehaviour
-        => AddBehaviour(Factory.BehaviourFactory.Instantiate<T>(_universeObject, args));
+    {
+        T behaviour = Factory.BehaviourFactory.Instantiate<T>(args);
+        return AddBehaviour(behaviour);
+    }
 
     public T? GetBehaviour<T>()
     {
@@ -125,27 +124,6 @@ public class BehaviourController : BaseEntity, IBehaviourController
             behaviour.Finalize();
     }
 
-    public void Update()
-    {
-        Debug.Assert.AssertInitialized(this);
-
-        if (!UniverseObject.StateEnable.Enabled || !StateEnable.Enabled)
-            return;
-
-        OnPreUpdate?.InvokeSafe(this);
-        OnUpdate?.InvokeSafe(this);
-    }
-
-    public void UpdatePreDraw()
-    {
-        Debug.Assert.AssertInitialized(this);
-
-        if (!UniverseObject.StateEnable.Enabled || !StateEnable.Enabled)
-            return;
-
-        OnPreDraw?.InvokeSafe(this);
-    }
-
     public BehaviourController() { }
     public BehaviourController(IUniverseObject universeObject) => Assign(universeObject);
 

Engine.Core/Factory/BehaviourFactory.cs

@@ -4,10 +4,10 @@ namespace Syntriax.Engine.Core.Factory;
 
 public class BehaviourFactory
 {
-    public static T Instantiate<T>(IUniverseObject universeObject, params object?[]? args) where T : class, IBehaviour
-        => Instantiate<T>(universeObject, stateEnable: null, args);
+    public static T Instantiate<T>(params object?[]? args) where T : class, IBehaviour
+        => Instantiate<T>(stateEnable: null, args);
 
-    public static T Instantiate<T>(IUniverseObject universeObject, 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);
@@ -18,8 +18,6 @@ public class BehaviourFactory
 
         if (!behaviour.Assign(stateEnable))
             throw AssignFailedException.From(behaviour, stateEnable);
-        if (!behaviour.Assign(universeObject.BehaviourController))
-            throw AssignFailedException.From(behaviour, universeObject.BehaviourController);
 
         return behaviour;
     }

Engine.Core/Systems/Abstract/IDraw.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified when the draw phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IDraw : IBehaviour
+{
+    /// <summary>
+    /// Calls draw logic for the <see cref="IBehaviour"/> to be displayed visually.
+    /// </summary>
+    void Draw();
+}

Engine.Core/Systems/Abstract/IFirstFrameUpdate.cs

@@ -0,0 +1,6 @@
+namespace Syntriax.Engine.Core;
+
+public interface IFirstFrameUpdate : IBehaviour
+{
+    void FirstActiveFrame();
+}

Engine.Core/Systems/Abstract/IPostDraw.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified after the draw phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IPostDraw : IBehaviour
+{
+    /// <summary>
+    /// Updates the state of the <see cref="IBehaviour"/> after the main draw phase happens.
+    /// </summary>
+    void PostDraw();
+}

Engine.Core/Systems/Abstract/IPostUpdate.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified after the update phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IPostUpdate : IBehaviour
+{
+    /// <summary>
+    /// Updates the state of the <see cref="IBehaviour"/> after the main update phase happens.
+    /// </summary>
+    void PostUpdate();
+}

Engine.Core/Systems/Abstract/IPreDraw.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified before the draw phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IPreDraw : IBehaviour
+{
+    /// <summary>
+    /// Updates the state of the <see cref="IBehaviour"/> before the main draw phase happens.
+    /// </summary>
+    void PreDraw();
+}

Engine.Core/Systems/Abstract/IPreUpdate.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified before the update phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IPreUpdate : IBehaviour
+{
+    /// <summary>
+    /// Updates the state of the <see cref="IBehaviour"/> before the main update phase happens.
+    /// </summary>
+    void PreUpdate();
+}

Engine.Core/Systems/Abstract/IUpdate.cs

@@ -0,0 +1,12 @@
+namespace Syntriax.Engine.Core;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> to be notified when the update phase of the <see cref="IUniverse"/> occurs.
+/// </summary>
+public interface IUpdate : IBehaviour
+{
+    /// <summary>
+    /// Updates the state of the <see cref="IBehaviour"/>.
+    /// </summary>
+    void Update();
+}

Engine.Core/Systems/DrawManager.cs

@@ -0,0 +1,51 @@
+
+namespace Syntriax.Engine.Core;
+
+public class DrawManager : UniverseObject
+{
+    private static System.Comparison<IBehaviour> SortByPriority() => (x, y) => y.Priority.CompareTo(x.Priority);
+
+    private readonly ActiveBehaviourCollectorSorted<IPreDraw> preDrawEntities = new() { SortBy = SortByPriority() };
+    private readonly ActiveBehaviourCollectorSorted<IDraw> drawEntities = new() { SortBy = SortByPriority() };
+    private readonly ActiveBehaviourCollectorSorted<IPostDraw> postDrawEntities = new() { SortBy = SortByPriority() };
+
+    private void OnPreDraw(IUniverse sender)
+    {
+        for (int i = preDrawEntities.Behaviours.Count - 1; i >= 0; i--)
+            preDrawEntities.Behaviours[i].PreDraw();
+    }
+
+    private void OnDraw(IUniverse sender)
+    {
+        for (int i = drawEntities.Behaviours.Count - 1; i >= 0; i--)
+            drawEntities.Behaviours[i].Draw();
+    }
+
+    private void OnPostDraw(IUniverse sender)
+    {
+        for (int i = postDrawEntities.Behaviours.Count - 1; i >= 0; i--)
+            postDrawEntities.Behaviours[i].PostDraw();
+    }
+
+    protected override void OnEnteringUniverse(IUniverse universe)
+    {
+        preDrawEntities.Assign(universe);
+        drawEntities.Assign(universe);
+        postDrawEntities.Assign(universe);
+
+        universe.OnPreDraw += OnPreDraw;
+        universe.OnDraw += OnDraw;
+        universe.OnPostDraw += OnPostDraw;
+    }
+
+    protected override void OnExitingUniverse(IUniverse universe)
+    {
+        preDrawEntities.Unassign();
+        drawEntities.Unassign();
+        postDrawEntities.Unassign();
+
+        universe.OnPreDraw -= OnPreDraw;
+        universe.OnDraw -= OnDraw;
+        universe.OnPostDraw -= OnPostDraw;
+    }
+}

Engine.Core/Systems/UpdateManager.cs

@@ -0,0 +1,71 @@
+
+using System.Collections.Generic;
+
+namespace Syntriax.Engine.Core;
+
+public class UpdateManager : UniverseObject
+{
+    private static System.Comparison<IBehaviour> SortByPriority() => (x, y) => y.Priority.CompareTo(x.Priority);
+
+    private readonly ActiveBehaviourCollectorSorted<IFirstFrameUpdate> firstFrameUpdates = new() { SortBy = SortByPriority() };
+    private readonly ActiveBehaviourCollectorSorted<IPreUpdate> preUpdateEntities = new() { SortBy = SortByPriority() };
+    private readonly ActiveBehaviourCollectorSorted<IUpdate> updateEntities = new() { SortBy = SortByPriority() };
+    private readonly ActiveBehaviourCollectorSorted<IPostUpdate> postUpdateEntities = new() { SortBy = SortByPriority() };
+
+    private readonly List<IFirstFrameUpdate> toCallFirstFrameUpdates = [];
+
+    protected override void OnEnteringUniverse(IUniverse universe)
+    {
+        firstFrameUpdates.Assign(universe);
+        preUpdateEntities.Assign(universe);
+        updateEntities.Assign(universe);
+        postUpdateEntities.Assign(universe);
+
+        universe.OnPreUpdate += OnPreUpdate;
+        universe.OnUpdate += OnUpdate;
+        universe.OnPostUpdate += OnPostUpdate;
+    }
+
+    protected override void OnExitingUniverse(IUniverse universe)
+    {
+        firstFrameUpdates.Unassign();
+        preUpdateEntities.Unassign();
+        updateEntities.Unassign();
+        postUpdateEntities.Unassign();
+
+        universe.OnPreUpdate -= OnPreUpdate;
+        universe.OnUpdate -= OnUpdate;
+        universe.OnPostUpdate -= OnPostUpdate;
+    }
+
+    private void OnPreUpdate(IUniverse sender, UniverseTime engineTime)
+    {
+        for (int i = toCallFirstFrameUpdates.Count - 1; i >= 0; i--)
+            toCallFirstFrameUpdates[i].FirstActiveFrame();
+
+        for (int i = preUpdateEntities.Behaviours.Count - 1; i >= 0; i--)
+            preUpdateEntities.Behaviours[i].PreUpdate();
+    }
+
+    private void OnUpdate(IUniverse sender, UniverseTime engineTime)
+    {
+        for (int i = updateEntities.Behaviours.Count - 1; i >= 0; i--)
+            updateEntities.Behaviours[i].Update();
+    }
+
+    private void OnPostUpdate(IUniverse sender, UniverseTime engineTime)
+    {
+        for (int i = postUpdateEntities.Behaviours.Count - 1; i >= 0; i--)
+            postUpdateEntities.Behaviours[i].PostUpdate();
+    }
+
+    private void OnFirstFrameCollected(IBehaviourCollector<IFirstFrameUpdate> sender, IFirstFrameUpdate behaviourCollected)
+    {
+        toCallFirstFrameUpdates.Add(behaviourCollected);
+    }
+
+    public UpdateManager()
+    {
+        firstFrameUpdates.OnCollected += OnFirstFrameCollected;
+    }
+}

Engine.Core/Universe.cs

@@ -9,7 +9,10 @@ public class Universe : BaseEntity, IUniverse
 {
     public event IUniverse.UpdateEventHandler? OnPreUpdate = null;
     public event IUniverse.UpdateEventHandler? OnUpdate = null;
-    public event IUniverse.PreDrawEventHandler? OnPreDraw = null;
+    public event IUniverse.UpdateEventHandler? OnPostUpdate = null;
+    public event IUniverse.DrawEventHandler? OnPreDraw = null;
+    public event IUniverse.DrawEventHandler? OnDraw = null;
+    public event IUniverse.DrawEventHandler? OnPostDraw = null;
 
     public event IUniverse.UniverseObjectRegisteredEventHandler? OnUniverseObjectRegistered = null;
     public event IUniverse.UniverseObjectUnRegisteredEventHandler? OnUniverseObjectUnRegistered = null;
@@ -116,21 +119,17 @@ public class Universe : BaseEntity, IUniverse
         Time = new(TimeSpan.FromTicks((long)(Time.TimeSinceStart.Ticks + engineTime.DeltaSpan.Ticks * TimeScale)), TimeSpan.FromTicks((long)(engineTime.DeltaSpan.Ticks * TimeScale)));
 
         OnPreUpdate?.InvokeSafe(this, Time);
-
-        for (int i = 0; i < UniverseObjects.Count; i++)
-            UniverseObjects[i].BehaviourController.Update();
-
         OnUpdate?.InvokeSafe(this, Time);
+        OnPostUpdate?.InvokeSafe(this, Time);
     }
 
-    public void PreDraw()
+    public void Draw()
     {
         Debug.Assert.AssertInitialized(this);
 
-        for (int i = 0; i < UniverseObjects.Count; i++)
-            UniverseObjects[i].BehaviourController.UpdatePreDraw();
-
         OnPreDraw?.InvokeSafe(this);
+        OnDraw?.InvokeSafe(this);
+        OnPostDraw?.InvokeSafe(this);
     }
 
     private void OnUniverseObjectFinalize(IInitializable initializable)

Engine.Physics2D/Abstract/Updates/IPostPhysicsUpdate.cs

@@ -0,0 +1,15 @@
+using Syntriax.Engine.Core;
+
+namespace Syntriax.Engine.Physics2D;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> that listens to the phase after the physics simulation phase.
+/// </summary>
+public interface IPostPhysicsUpdate : IBehaviour
+{
+    /// <summary>
+    /// Execute logic that should occur after the physics simulation has been updated.
+    /// </summary>
+    /// <param name="delta">The time elapsed since the last physics update, typically in seconds.</param>
+    void PostPhysicsUpdate(float delta);
+}

Engine.Physics2D/Abstract/Updates/IPrePhysicsUpdate.cs

@@ -0,0 +1,15 @@
+using Syntriax.Engine.Core;
+
+namespace Syntriax.Engine.Physics2D;
+
+/// <summary>
+/// Represents a <see cref="IBehaviour"/> that listens to the phase before the physics simulation phase.
+/// </summary>
+public interface IPrePhysicsUpdate : IBehaviour
+{
+    /// <summary>
+    /// Execute logic that should occur before the physics simulation is updated.
+    /// </summary>
+    /// <param name="delta">The time elapsed since the last physics update, typically in seconds.</param>
+    void PrePhysicsUpdate(float delta);
+}

Engine.Physics2D/PhysicsEngine2D.cs

@@ -14,9 +14,12 @@ public class PhysicsEngine2D : UniverseObject, IPhysicsEngine2D
     protected readonly ICollisionDetector2D collisionDetector = null!;
     protected readonly ICollisionResolver2D collisionResolver = null!;
 
+    private static System.Comparison<IBehaviour> SortByPriority() => (x, y) => y.Priority.CompareTo(x.Priority);
+    protected ActiveBehaviourCollectorSorted<IPrePhysicsUpdate> physicsPreUpdateCollector = new() { SortBy = SortByPriority() };
+    protected ActiveBehaviourCollectorSorted<IPhysicsUpdate> physicsUpdateCollector = new() { SortBy = SortByPriority() };
+    protected ActiveBehaviourCollectorSorted<IPostPhysicsUpdate> physicsPostUpdateCollector = new() { SortBy = SortByPriority() };
     protected BehaviourCollector<IRigidBody2D> rigidBodyCollector = new();
     protected BehaviourCollector<ICollider2D> colliderCollector = new();
-    protected BehaviourCollector<IPhysicsUpdate> physicsUpdateCollector = new();
 
     public int IterationPerStep { get => _iterationPerStep; set => _iterationPerStep = value < 1 ? 1 : value; }
     public float IterationPeriod { get => _iterationPeriod; set => _iterationPeriod = value.Max(0.0001f); }
@@ -25,6 +28,12 @@ public class PhysicsEngine2D : UniverseObject, IPhysicsEngine2D
     {
         float intervalDeltaTime = deltaTime / IterationPerStep;
 
+        foreach (IPrePhysicsUpdate physicsPreUpdate in physicsPreUpdateCollector)
+            physicsPreUpdate.PrePhysicsUpdate(deltaTime);
+
+        foreach (IPhysicsUpdate physicsUpdate in physicsUpdateCollector)
+            physicsUpdate.PhysicsUpdate(deltaTime);
+
         for (int iterationIndex = 0; iterationIndex < IterationPerStep; iterationIndex++)
         {
             // Can Parallel
@@ -92,8 +101,8 @@ public class PhysicsEngine2D : UniverseObject, IPhysicsEngine2D
             OnPhysicsIteration?.InvokeSafe(this, intervalDeltaTime);
         }
 
-        foreach (IPhysicsUpdate physicsUpdate in physicsUpdateCollector)
-            physicsUpdate.PhysicsUpdate(deltaTime);
+        foreach (IPostPhysicsUpdate physicsPostUpdate in physicsPostUpdateCollector)
+            physicsPostUpdate.PostPhysicsUpdate(deltaTime);
 
         OnPhysicsStep?.InvokeSafe(this, deltaTime);
     }
@@ -109,7 +118,9 @@ public class PhysicsEngine2D : UniverseObject, IPhysicsEngine2D
 
     protected override void OnEnteringUniverse(IUniverse universe)
     {
+        physicsPreUpdateCollector.Assign(universe);
         physicsUpdateCollector.Assign(universe);
+        physicsPostUpdateCollector.Assign(universe);
         colliderCollector.Assign(universe);
         rigidBodyCollector.Assign(universe);
 
@@ -118,7 +129,9 @@ public class PhysicsEngine2D : UniverseObject, IPhysicsEngine2D
 
     protected override void OnExitingUniverse(IUniverse universe)
     {
+        physicsPreUpdateCollector.Unassign();
         physicsUpdateCollector.Unassign();
+        physicsPostUpdateCollector.Unassign();
         colliderCollector.Unassign();
         rigidBodyCollector.Unassign();