Ball Pit is an immersive 3D game. It's best played standing up, because you have to be able to spin around to see everything that happens around you. Ball Pit only works on iPhone 4 and later, since it needs the gyroscope to tell which way you're looking.
Version 2.2 uses the full screen on all devices. And I mean the full screen -- no more banner ads!
Get Ball Pit from the App Store