anchor.diff:    static const int rendering = 0;
     static const int physics = 1;
   
  +  final StreamController<bool> _pauseStreamController =
  +      new StreamController<bool>();
     final CanvasElement canvas;
     final CanvasRenderingContext ctx;
     final GameHelper helper;
  
positive.code:   void pause() {
      if (!_stop) {
        _pause = true;
      }
    }
  
    bool get paused => _pause;
  
negative.code: 
    void stop() {
      _stop = true;
      _pauseStreamController.close();
    }
  
    bool get isStopped => _stop;
  