anchor.diff:  
       game.stage.onKeyUp.listen((value) {
         switch (value.keyCode) {
  -        case leftArrow:
  +        case KeyCode.LEFT:
             player.movingLeft = false;
             break;
  -        case rightArrow:
  +        case KeyCode.RIGHT:
             player.movingRight = false;
             break;
         }
  
positive.code: 
      game.stage.onKeyDown.listen((value) {
        switch (value.keyCode) {
          case leftArrow:
            player.movingLeft = true;
            break;
          case rightArrow:
            player.movingRight = true;
            break;
        }
  
negative.code:     Text scoreText = new Text(this, "Score: $score", size: 20);
  
      Button leftButton = new Button(this, "leftButton", "L");
      leftButton.setCoordinates(0, game.stage.sourceHeight - 100);
  
      Button rightButton = new Button(this, "rightButton", "R");
      rightButton.setCoordinates(game.stage.sourceWidth -
          rightButton.width.toInt(), game.stage.sourceHeight - 100);
  
      Ship player = new Ship(this, "ship")
          ..x = game.stage.sourceWidth ~/ 2
          ..y = game.stage.sourceHeight - 200
          ..vx = 300;
  
      leftButton.onTouchBegin.listen((_) {
  