Hello. Its an old post but i where looking through them anyways
You dont need any variables.
You dont need "destroy outside layout"
On start - disable gravity and destroy the ball and bullet C2 needs (Not need i would say, since you could place them outside the margin)
Add a margin and set up your balls and bullet, that if they exceed the margin, destroy them.
Spawn bullets and balls at a interval - in the margin.
The Coding You should move the "Physics force" to a seperay event, that only apply´s when a ball is created - otherwise its gonna do it every 0.5 two times just realised now when i where looking at the image. Woops.