anchor.diff:      _move();
       _draw(ctx);
     }
  -
  -  Point get head => _body.first;
   }
   
   class Keyboard {
  
positive.code: }
  
  class Snake {
    static const Point RIGHT = const Point(1, 0);
    static const Point LEFT = const Point(-1, 0);
    static const Point UP = const Point(0, -1);
    static const Point DOWN = const Point(0, 1);
  
    static const int START_LENGTH = 6;
  
    List<Point> _body = [];   // coordinates of the body segments
    Point _dir = RIGHT;       // current travel direction
  
    Snake() {
  
negative.code: 
      if (diff > GAME_SPEED) {
        _lastTimestamp = delta;
        clear();
        drawCell(_food, "blue");
        _snake.update(ctx, _keyboard);
        _checkForCollisions();
      }
  
  