We've had a thread in our forums cookin' for a while now for the upcoming game Super Planet Defender which actually has been slowly drizzling out beta releases on Android. The object of the game is to survive as long as you can in a world where your planet is just being absolutely bombarded with comets and other astral bodies. Check it out in action:

As the game progresses, the comet spawn rate increases and different types of comets enter the fray. There's a whole bunch of weapons to unlock, along with an eventual hard mode which hopefully is packed with even more screen flashing and particle effects.

According to the developer, Super Planet Defender should hit the App Store in a few weeks, but if you've got an Android device this is one of the few times that you can actually get a game first.