Nice so far
I like the idea of the game, it has a lot of promise but some things need improvement. Biggest problem out of the way first, the swing physics. I am under the impression that rubber physics are quite tough but you need to tweak some more. The ball slings back at my craft right after a sling, rather then sling outward so i can sling it round proper.
Graphics could use some polish, nice and simple is one, but a background is nice too.
Your sound needs a few lines of code extra, every time i restart another loop begins, so i hear 3 loops together which sounds horrendous. And i want massive explosive sounds! I want to regret putting my volume on full!