www.factorio.com - there's a demo with enough in it to show you what the game is about.
Slick little alpha game that's kind of a mix of gathering, building, sim, strategy, rts. It's damn solid for an early release. They're going for steam greenlight and it's not a widely known title, but it's a crazy fun and different game.
You basically build a factory...which sounds...simple enough...until you play it and see how complicated that can be. 
As my brother has said, we shouldn't recommend this game to any gamers with OCD tendencies because it will make you *twitch* as you reiterate, redesign, perfect, optimize, etc.