anchor.diff:        ..runAction(controller2);
   
       var ballbody = new ArcadeBody()
  -      ..speed = new Vector2(-300.0, 400.0)
  +      ..speed = new Vector2(-300.0, 200.0)
         ..restitution = new Vector2(1.0, 1.0)
         ..addTo(world);
   
  
positive.code:     body2.collider = new AABB2Collider();
      body2.collider.body = body2;
      var paddle2Collision = new StaticBodyVsBodyCollisionCheck()
            ..collider1 = body2.collider
            ..collider2 = ballbody.collider;
      paddle2Collision.onCollision.listen((event) {
        ballbody.position.add(event.delta);
        ballbody.speed.reflect(event.delta.normalized());
        ballbody.syncToNode();
      });
      world.collisions.add(paddle2Collision);
    });
  
    game.start();
  
negative.code:     wallsCollision.collider1 = ballbody.collider;
      wallsCollision.collider2 = world.collider;
      wallsCollision.onCollision.listen((event) {
        ballbody.position.add(event.delta);
        if (event.delta.x != 0.0) {
          ballbody.speed.reflect(new Vector2(event.delta.x.sign, 0.0));
        }
        if (event.delta.y != 0.0) {
          ballbody.speed.reflect(new Vector2(0.0, event.delta.y.sign));
        }
        ballbody.syncToNode();
      });
      world.collisions.add(wallsCollision);
  