anchor.diff:              scoreText.text = "Score: ${score+=10}";
             }
           });
  -        if(ufo.hitTestObject(player)){
  +        if (ufo.hitTestObject(player)) {
             game.stage.removeEventListeners("keyDown");
             bulletTimer.cancel();
             killteState();
  
positive.code: 
  
      Sprite bullet;
      Timer bulletTimer = new Timer.periodic(new Duration(milliseconds: 450), (_) {
        if (bullets.any((item) => !item.alive)) {
          bullet = bullets.firstWhere((item) => !item.alive)
              ..x = player.x
  
negative.code:     int score = 0;
      Text scoreText = new Text(this, "Score: $score", size: 20);
  
      Button leftButton = new Button(this, "leftButton", "")
          ..x = 10
          ..y = 510;
  
      Button rightButton = new Button(this, "rightButton", '')
          ..x = 710
          ..y = 510;
  
      Ship player = new Ship(this, "ship")
          ..center()
          ..x = 400
          ..y = 500
          ..vx = 300;
  
      leftButton.onMouseDown.listen((_) {
        player.movingLeft = true;
      });
  
      leftButton.onMouseUp.listen((_) {
        player.movingLeft = false;
      });
  
      rightButton.onMouseDown.listen((_) {
        player.movingRight = true;
      });
  
      rightButton.onMouseUp.listen((_) {
        player.movingRight = false;
      });
  
  
      Group<Sprite> bullets = new Group<Sprite>();
  