acquired Turtle Rock Studios, developers of the upcoming zombie survival game Left 4 Dead. The company has also contributed various maps for Counter-Strike: Source, including a remake of cs_militia. Given Turtle Rock's close relationship with Valve, we're not too surprised by this move. Previously, Valve has hired developers of Counter-Strike, Team Fortress and Narbacular Drop, the latter title serving as a spiritual precursor for Portal.
Left 4 Dead, originally announced November 2006 and utilizing the Source Engine, is a four-player co-op game where a team of survivors take on a horde of zombies and four player-controlled "super zombies." It is slated for release later this year.