code: function() {
  
  		this._is_reversed = !this._is_reversed;
  
  		if (this._is_running) {
  
  			var now = new Date().getTime(),
  				new_end = 2 * now - this._started_time;
  
  			// it's possible in case of script lags. Must not allow negative transition values.
  			if (now > this._end_time) {
  
  				this._started_time = this._end_time;
  				this._end_time = this._started_time + this._duration;
  
  			} else {
  
  				this._end_time = new_end;
  				this._started_time = new_end - this._duration;
  
  			}
  
  			this._afterMirror(now);
  
  		}
  
  	}
docs: Reverse animation direction