anchor.diff:    num _lastTimestamp = 0;
     int _rightEdgeX;
     int _bottomEdgeY;
  -
  -  Keyboard _keyboard = new Keyboard();
   
     Snake _snake;
     Point _food;
  
positive.code: 
  CanvasElement canvas;
  CanvasRenderingContext2D ctx;
  
  void main() {
    canvas = querySelector('#canvas')..focus();
  
negative.code:       _lastTimestamp = delta;
        clear();
        drawCell(_food, "blue");
        _snake.update();
        _checkForCollisions();
      }
  
  