Valve acquires Turtle Rock

Valve has acquired Turtle Rock Studios, the Orange County-based developer behind Left 4 Dead, a multiplayer coop that uses the Source engine.
The merger of the two companies extends Valve’s development team and provides the company with a new studio in southern California.
Valve and Turtle Rock aren’t exactly strangers since the two have collaborated on several projects, including a number of Counter-Strike: Source maps, Condition Zero, and the Xbox port of Counter-Strike.