I'm making my SS clone in game maker, it contains all the functions an SS game needs, except the mmorpg multiplayer might be a bit difficult :/
p.s might i direct you to
http://www.fpscreator.com/
the full version costs an arm and a leg but you can probably find some hax somewhere or something.
game maker is really only for 2d games, no matter how much they say otherwise. i'm working out planetary physics and how to get moons to rotate around planets, and also working on a money encryption algorithm to prevent haxxors.