Bungie's Duality, modified with Bobs that shoot grenades or lava globs. The idea is to give people without access to a network the challenge of a net game. (SPN stands for Single Player Network.) Works okay, except that bobs will never shoot like real people... and not much care was taken with the physics model. (Although the shots are right, the sounds aren't... sort of strange when you hear pistol shots,and turn around to see lava globs coming at you.)