Nice game, some improvements came to my mind:
- after a shot the ball takes a while to stop completely, I would try to increase linear damping a bit, assuming you use box2d
- after passing a level it would be nice to have a button to directly proceed to the next level
There were no ads to ruin gameplay, thank you!

Thanks very much for the feedback, it's always good to get some actual suggestions on what to improve.
The only tricky part of moving directly to the next level is the average grade mechanism means completing doesn't necessarily unlock the next level. Obviously I can and should still do it, but I've been kicking that can down the road because of it. It annoys the hell out of me when testing now though, so I think that just got bumped up to the top of my todo list.
I do use Box2D, I've actually had a few people say the same thing about the slow down time. I did alter it, but apparently not enough! That's a nice quick change though, so might roll it into the next update tomorrow.
Got some more levels coming tomorrow too, plus I have tweaked some of the earlier ones to make the difficulty a bit less random (the third level was significantly easier than the first 2).
Thanks again for downloading and giving me your thoughts, really helpful.