 
 		private static var _now:Number;
 
+		/**
+		 * 设置或获取当前时间
+		 * @return
+		 *
+		 */
 		public static function get now():Number
 		{
 			return _s.now;

		 */
		public static var camera:Camera2D = new Camera2D();

		private static var _s:Engine;

		/**


		private static var _onStart:Signal;

		/**
		 * 启动时广播
		 * @return
		 *
		 */
		public static function get onStart():Signal
		{
			return _onStart ||= new Signal();
