anchor.diff:  
       world.collisions.add(paddle1wallCollision);
       world.collisions.add(paddle2wallCollision);
  +
  +    game.keyboard.onKeyDown.where(((e) => e.keyCode == Keys.SPACE)).listen((e) {
  +      ballbody.speed.setValues(100.0, 200.0);
  +    });
     });
   
     game.start();
  
positive.code:     body2.syncFromNode();
  
      var ballbody = new ArcadeBody()
        ..position = new Vector2(400.0, 300.0)
        ..speed = new Vector2(-100.0, 200.0)
        ..restitution = new Vector2(1.0, 1.0)
        ..addTo(world);
  
  
negative.code:     wallsCollision.collider1 = ballbody.collider;
      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);
        }
      });
      world.collisions.add(wallsCollision);
  
      body1.collider = new AABB2Collider();
  