Game Basics Sorted

I've got most of the basic, lowdown stuff on my game, Stable Orbit. The idea behind the game is that we have been forced to evacuate the Earth after a major catastrophe. We can't live on the moon (like, there's no air) so we ought to build ourselves a new moon to live on (Do not try this at home). Once Moon II is released the control belongs to gravity. Needless to say, crashes with Earth or Moon I are forbidden, as is letting Moon II fly off into outer space. You'll need to survive until the Earth is safe again. Oh, and, what when it gets full. Gravity simulation is done, as is collision detection. Most of the none-UI graphics are done but I still need a UI, sound, and some way of controlling the creation of this new planet.