Left 4 Dead is a new action title from Valve, creators of the Counter-Strike and Half-Life games, and promises to redefine the co-operative genre as those titles did for multiplayer and single player action games.
ESRB - Adults Only 18+: Titles rated AO (Adults Only) have content that should only be played by persons 18 years and older. Titles in this category may include prolonged scenes of intense violence and/or graphic sexual content and nudity.
