anchor.diff:    }
   
     void _checkInput(Keyboard keyboard) {
  -    if (keyboard.isPressed(KeyCode.RIGHT) && _dir != LEFT) {
  +    if (keyboard.isPressed(KeyCode.LEFT) && _dir != RIGHT) {
  +    _dir = LEFT;
  +    }
  +    else if (keyboard.isPressed(KeyCode.RIGHT) && _dir != LEFT) {
         _dir = RIGHT;
  -    }
  -    else if (keyboard.isPressed(KeyCode.LEFT) && _dir != RIGHT) {
  -      _dir = LEFT;
       }
       else if (keyboard.isPressed(KeyCode.UP) && _dir != DOWN) {
         _dir = UP;
  
positive.code:     _body = new List<Point>.generate(START_LENGTH, (int index) => new Point(i--, 0));
    }
  
    void _draw(CanvasRenderingContext2D ctx) {
      // starting with the head, draw each body segment
      for (Point p in _body) {
        drawCell(ctx, p, "green");
      }
    }
  
  
negative.code:     _move();
      _draw(ctx);
    }
  }
  
  class Keyboard {
  