Valve officially announced Left 4 Dead 2, the sequel to the successful cooperative first-person shooter Left 4 Dead.
Left 4 Dead 2 was released for Microsoft Windows and Xbox 360. The game featured new campaigns, characters, and infected enemies.
The Mac OS X version of Left 4 Dead 2 was released via Steam, expanding the game's platform availability.
Left 4 Dead 2 was released on Linux, further extending the game's compatibility.