BattlePaint, you play a cube. In fact, you're not even a cube -- just a square. But boy, are you fast! And you can shoot in all directions. That's important, because there are baddies coming in from all over the place.
The "baddies" are swarms of other squares, in all sorts of pretty colors. They track you all over the screen, and you run around very quickly and just shoot, shoot, and shoot some more. If that doesn't sound very emotionally deep, it's because it isn't. But it's fun!
After you shoot a baddy, it splashes paint as it disappears. You need to skate across this blob of paint and "eat it up" to get points. This game is fast. It clocked in at around 60-70 FPS on my system, and was loads of fun to play. It does tend to insult you when you die, though, but don't be offended -- I don't think it's personal.