Left 4 Dead is a co-operative, survival horror, first-person shooter video game. It was developed by Turtle Rock Studios, who were purchased by the Valve Corporation part-way into development. The game uses the Source game engine, and is available for Windows-based personal computers and the Xbox 360.
The game pits four Survivors of an apocalyptic pandemic against hordes of aggressive zombies. There are two game modes: a four-player, co-op Campaign mode, and an eight-player Versus mode. In both modes an AI, dubbed "The Director", controls level pacing and item spawns, in an attempt to create a dynamic experience and increase replay value.
