anchor.diff:          ctx = webgl
               ? (querySelector(canvasSelector) as CanvasElement).getContext3d()
               : (querySelector(canvasSelector) as CanvasElement).context2D
  -            as CanvasRenderingContext,
  +                as CanvasRenderingContext,
           _width = width,
           _height = height {
       canvas.width = width;
  
positive.code:   void resume() {
      if (!_stop && _pause) {
        _pause = false;
        _startGameLoops();
      }
    }
  
negative.code:   void pause() {
      if (!_stop) {
        _pause = true;
        _pauseStreamController.add(true);
      }
    }
  
    Stream<bool> onPause() {
      return _pauseStreamController.stream;
    }
  
    bool get paused => _pause;
  