 		public function get first():Entity { return _updateFirst; }
 		
 		/**
+		 * How many Entity layers the World has.
+		 */
+		public function get layers():uint { return _layerList.length; }
+		
+		/**
 		 * The first Entity of the type.
 		 * @param	type		The type to check.
 		 * @return	The Entity.

			if (e._renderPrev) e._renderPrev._renderNext = e._renderNext;
			else
			{
				_renderFirst[e._layer] = e._renderNext
				if (!e._renderNext)
				{
					_layerList[_layerList.indexOf(e._layer)] = null;
					_layerSort = true;
				}
			}
			_layerCount[e._layer] --;

			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;
