 			var f:Entity = _renderFirst[e._layer];
 			if (f)
 			{
+				// Append entity to existing layer.
 				e._renderNext = f;
 				f._renderPrev = e;
 				_layerCount[e._layer] ++;
 			}
 			else
 			{
+				// Create new layer with entity.
 				_renderLast[e._layer] = e;
 				_layerList[_layerList.length] = e._layer;
 				_layerSort = true;

		public function get first():Entity { return _updateFirst; }
		
		/**
		 * The first Entity of the type.
		 * @param	type		The type to check.
		 * @return	The Entity.

			if (e._typePrev) e._typePrev._typeNext = e._typeNext;
			e._typeNext = e._typePrev = null;
			_typeCount[e._type] --;
		}
		
		/** @private Calculates the squared distance between two rectangles. */
