NASA has a free game app based upon the Rosetta mission to a comet:
We are excited to announce another free NASA iPhone/iPad game created by the Space Place team. Learn about comets and the Rosetta mission while playing the fast-moving, immersive action game “Comet Quest.” It’s like the real Rosetta mission, but with you in control of the spacecraft: First, drop the comet lander carefully onto the nucleus; observe and record gas jets, craters, cracks, and other happenings; dodge and dart around ice chunks flying off the nucleus; and, in your spare time, communicate with the lander and with Earth. Find it at the Apple app store at http://itunes.apple.com/us/app/comet-quest/id504786625?mt=8&ls=1.
While at at the Apple Store make sure you browse through the free Yale University Open courses and other FREE classes. There are astronomy courses through Yale and in other free Apple offerings courses on Moons. Very, very cool. I look forward to taking these as a refresher.