anchor.diff:  class GridRenderer2D {
     CanvasRenderingContext2D canvas;
   
  -  String gold_color = "#FFD700";
  -   String white_color = "#FFFFFF";
  +  String gold_color =  "#FFD700";
  +  String white_color = "#FFFFFF";
  +
   
     static Coord snakePenSizeInPixels = new Coord(640, 480);
     static Coord gridBlockSizeInPixels = new Coord(10, 10);
  
positive.code:   }
  
    void clearCanvas() {
      var gc = canvas.canvas.getContext('2d');
      canvas.fillStyle = white_color;
      canvas.fillRect(0, 0, gridBlockSizeInPixels.getX(), gridBlockSizeInPixels.getY());
    }
  
    void renderGridBlock(final Coord c, final String color) {
  
negative.code:     canvas.fillRect(gridBlockSizeInPixels.getX() * c.getX(),
          gridBlockSizeInPixels.getY() * c.getY(), gridBlockSizeInPixels.getX(),
          gridBlockSizeInPixels.getY());
    }
  
    void fillCanvas(String color) {
      canvas.fillStyle = color;
      canvas.fillRect(0, 0, snakePenSizeInPixels.getX(),
      snakePenSizeInPixels.getY());
    }
  }
  
  