diff --git a/Engine.Physics2D/PhysicsEngine2D.cs b/Engine.Physics2D/PhysicsEngine2D.cs
index 21fca43..0b63c59 100644
--- a/Engine.Physics2D/PhysicsEngine2D.cs
+++ b/Engine.Physics2D/PhysicsEngine2D.cs
@@ -12,8 +12,9 @@ public class PhysicsEngine2D : IPhysicsEngine2D
     private readonly List<ICollider2D> colliders = new(64);
 
     private int _iterationCount = 1;
-    private ICollisionDetector2D collisionDetector = new CollisionDetector2D();
-    private ICollisionResolver2D collisionResolver = new CollisionResolver2D();
+
+    private readonly ICollisionDetector2D collisionDetector = null!;
+    private readonly ICollisionResolver2D collisionResolver = null!;
 
     public int IterationCount { get => _iterationCount; set => _iterationCount = value < 1 ? 1 : value; }
 
@@ -122,4 +123,16 @@ public class PhysicsEngine2D : IPhysicsEngine2D
 
         colliders.Remove(collider2D);
     }
+
+    public PhysicsEngine2D()
+    {
+        collisionDetector = new CollisionDetector2D();
+        collisionResolver = new CollisionResolver2D();
+    }
+
+    public PhysicsEngine2D(ICollisionDetector2D collisionDetector, ICollisionResolver2D collisionResolver)
+    {
+        this.collisionDetector = collisionDetector;
+        this.collisionResolver = collisionResolver;
+    }
 }
diff --git a/Engine.Physics2D/PhysicsEngine2DCacher.cs b/Engine.Physics2D/PhysicsEngine2DCacher.cs
index 30b3f95..d691355 100644
--- a/Engine.Physics2D/PhysicsEngine2DCacher.cs
+++ b/Engine.Physics2D/PhysicsEngine2DCacher.cs
@@ -14,8 +14,9 @@ public class PhysicsEngine2DCacher : IPhysicsEngine2D, IAssignableGameManager
 
     private int _iterationCount = 1;
 
-    protected ICollisionDetector2D collisionDetector = new CollisionDetector2D(); // TODO Dependency Injection or Reversion
-    protected ICollisionResolver2D collisionResolver = new CollisionResolver2D(); // TODO Dependency Injection or Reversion
+    protected readonly ICollisionDetector2D collisionDetector = null!;
+    protected readonly ICollisionResolver2D collisionResolver = null!;
+
     protected BehaviourCacher<IRigidBody2D> rigidBodyCacher = new();
     protected BehaviourCacher<ICollider2D> colliderCacher = new();
 
@@ -121,6 +122,29 @@ public class PhysicsEngine2DCacher : IPhysicsEngine2D, IAssignableGameManager
         return true;
     }
 
-    public PhysicsEngine2DCacher() { }
-    public PhysicsEngine2DCacher(IGameManager gameManager) => Assign(gameManager);
+    public PhysicsEngine2DCacher()
+    {
+        collisionDetector = new CollisionDetector2D();
+        collisionResolver = new CollisionResolver2D();
+    }
+
+    public PhysicsEngine2DCacher(IGameManager gameManager)
+    {
+        Assign(gameManager);
+        collisionDetector = new CollisionDetector2D();
+        collisionResolver = new CollisionResolver2D();
+    }
+
+    public PhysicsEngine2DCacher(IGameManager gameManager, ICollisionDetector2D collisionDetector, ICollisionResolver2D collisionResolver)
+    {
+        Assign(gameManager);
+        this.collisionDetector = collisionDetector;
+        this.collisionResolver = collisionResolver;
+    }
+
+    public PhysicsEngine2DCacher(ICollisionDetector2D collisionDetector, ICollisionResolver2D collisionResolver)
+    {
+        this.collisionDetector = collisionDetector;
+        this.collisionResolver = collisionResolver;
+    }
 }