Osmos HD 1.6.4
the author of this app says:
Experience the awesomeness Apple named "iPad App of the Week," GameAndPlayer called "a work of genius," and IGN said is "The best iPad game yet." Osmos is part physics-based eat-'em-up, part ambient, cosmic simulator, and part Darwinistic game of survival. This award-winning PC game has been fully redesigned for the iPad, featuring fluid multitouch controls, lush, flowing visuals, and a chill, ambient electronic soundtrack.
Some describe Osmos as "Asteroids meets a lava-lamp," others as "Katamari meets Lunar Lander," but all have said it's a game you must experience to appreciate. Your goal is to grow by absorbing smaller motes, but to propel yourself you must eject matter behind you, causing you to shrink. From this fundamental balance, Osmos leads the player through ambient playgrounds, deep solar systems, competitive petri dishes, dense mote-fields, and more.
Compatible with iPad. Requires iOS 3.2 or later