Really nice game. You got around the potential frustration of the "trial and error" approach of physics puzzles by not limiting the player with the number of moons they had to experiment with, and by not requiring a level reload. This allowed for quick iteration. The graphics were simple but effective, and the background music was appropriately "celestial". I thought it was clever that you required a certain number of orbits before calling a level a success, to check that it was stable. A couple more mechanics (perhaps requiring the orbit to be within a particular range from the planet, or having differently sized moons) and some more levels and you'd have a very nice tablet / phone game.