Left 4 Dead - Episode 1

Left 4 Dead (abbreviated L4D) is a singleplayer and multiplayer cooperative survival horror FPS game developed by Valve Corporation and Turtle Rock Studios. The game was built using Source engine and is available on PC and Xbox 360. During early development, its working title was "Terror Strike."

The game puts four human playable or AI-controlled Survivors of an apocalyptic pandemic against Hordes of the Infected. Regular Infected are controlled by the game AI, while human players can control up to four mutated Special Infected with special abilities in Versus mode. The goal of Left 4 Dead for the Survivors is to help each other make it through a level to safety. Infected players must cooperate to stop them.