Examiner.com | Alien Swarm: Let the Modding Begin!

Examiner.com: "Released on July 19, 2010 Alien Swarm is Valve's love letter to their PC gaming audience. It features four-player co-op, 64 Steam Achievements, four different classes and eight unique characters. Though it's a very small game and the graphics aren't bleeding-edge fantastic, it's an absolute steal at the bargain price of $0.00."