Announcement - Valve
2012 年 07 月 24 日
During this week's Midweek Madness, save 75% off the Left 4 Dead 2!

Also, make sure to check out the "Cold Stream" update today! This 5 campaign DLC includes Crash Course, Death Toll, Dead Air, Blood Harvest and the community created Cold Stream. The update also makes all mutations available to play any time.