Basically, a meteor has hit the Moon, and damaged the life support devices that keep alive your colony, and you need to repair the equipment within 25 minutes, or all the oxygen will run out and your friends will die!

That's an oversimplified description, but the game has great graphics, and awesome multiplayer, and it's free.

Here's the Game's Website: http://www.moonbasealphagame.com/

Here's the Trailer: http://www.youtube.com/watch?v=nis2t9EubBs

Get it here: http://store.steampowered.com/app/39000/