anchor.diff:      });
   
       var paddle2wallCollision = new StaticBodyOutOfBoundsCollisionCheck()
  -
         ..collider1 = body2.collider
         ..collider2 = world.collider;
   
  
positive.code:     wallsCollision.collider2 = world.collider;
      wallsCollision.onCollision.listen(bounce);
      wallsCollision.onCollision.listen((event) {
        if (event.delta.x != 0.0) {
          ballbody.position.setValues(400.0, 200.0);
          ballbody.speed.setValues(0.0, 0.0);
        }
  
negative.code: 
    loader.load().last.then((p) {
      game.scene.onFrame.listen(world.update);
  
      var score1 = 0;
      var score2 = 0;
  
      var message = new Label('Press space to start')
            ..addTo(game.scene)
            ..align = 'center'
            ..position = new Vector2(400.0, 40.0);
  
      var counter1 = new Label(score1.toString())
        ..addTo(game.scene)
        ..align = 'center'
        ..position = new Vector2(20.0, 40.0);
  
      var counter2 = new Label(score1.toString())
        ..addTo(game.scene)
        ..align = 'center'
        ..position = new Vector2(780.0, 40.0);
  
      var controller1 = new ArcadeKeyboardController(game.keyboard)
        ..keyUp = Keys.A
  