When there is room, you must shoot the next number so that it does not crash into a spoke.
The Good: 'aa' is fast, fun and very addictive.
The Bad: The game doesn't vary much. Sometimes the wheel will spin clockwise, sometimes counter clockwise. That's basically it.
The Ugly: multiple times, I was very patient, waiting for the wheel to spin and shoot into a gap.....when suddenly, the program thinks that there's been a collision. This has happened maybe 10 times to me so far.
The miscellaneous: I was stuck on level 26 for at least an hour. Now I'm stuck on level 49 and I don't think I'll get past it. Would you believe that there are 525 'entirely unique' levels? Once you've done 48 levels, that's enough. If you want to play a genuine variation, look for their other apps: ff, au, rr and uu.