Nice graphics and physics!
I think you should try out some different mechanics for shooting the ball. Right now it's a bit confusing how to aim sometimes.
One way would be to keep finger pressed while aiming, and that it at the same time shows an arrow pointing from the ball so you know the direction it'll go.
Or you could try an Angry Bird-type control, where you drag behind the ball to aim and release to shoot. That way you could also control the power of the shot. However, you would have to adjust some levels so you have space to actually drag behind the ball.
There's also some slight lag on the start screen, and when shooting the ball sometimes, that might need look into.
Good job so far!