Not bad at all for a first effort, I see what you were trying to achieve with rotation.
I see you can just sit there and wait for the colors to change on targets, then launch. I found a spot for my mouse that would pretty much guarantee me hitting the first target and then I got 100 points every time, just as long as I waited.
Maybe to prevent this and add some tension, you could have a timed mode? Limited amount of balls, perhaps? I never seemed to run out.
It reminded me of "Peggle", used to have lots of fun with all the various minigames there, back in the day. Maybe give that a look, get some ideas ;)