anchor.diff:    void clearCanvas() {
       // final CanvasElement canvas = querySelector("#myCanvas");
       var gc = canvas.canvas.getContext('2d');
  -    gc.fillStyle = "#FFFFFF";
  +    gc.fillStyle = white_color;
       gc.fillRect(0, 0, cwidth, cheight);
     }
   
  
positive.code:     crc.fillStyle = color;
      crc.fillRect(width * x, height * y, width, height);
    }
  }
  
  class Snake {
  
negative.code:   }
  
    void render(canvas) {
      coords.forEach((c) => c.render(canvas, white_color));
    }
  
    void increaseTail() {
  