 	// MARK: - Static
 	internal static var stack = SceneStack()
 	
-	// MARK: - Top Level References
+	// MARK: - Top Level Objects
 	
 	private var topLevelGameObjects = [GameObject]()
 	

		
		initializeRoot()
		
		// postprocess scene into GameObjects, Components...
		
		self.setup()
	}

	private func initializeRoot() {
		self.root.delegateScene = self
		self.root.physicsWorld.contactDelegate = self.root
		
		self.ambientLightSource.categoryBitMask = ~(.allZeros)	// apply to all categories
		self.root.addChild(self.ambientLightSource)
	}
	
	// MARK: - Properties
