The concept is tough to explain, but once you see it in action, you'll understand right away. The goal is to move the stage at the right time in order to keep the ball bouncing around where you want it. It's actually really fun, despite the simplicity, and over the 20 various stages, there are some pretty clever puzzles. The game also has OpenFeint integration, and the 8-bit music is pretty catchy as well.
It's a good deal for only 99 cents. There's also a lite version to try out if you just want to see how it works. I can't see anyone really disliking the game, but it is fairly simple. Still, at just a buck, it's worth a purchase just to have it to pick up and play when you need a mindless little reflex game.