ESRB Rating: M - Mature Genre: Shooter Features: Addictive co-op action gameplay from the makers of Counter-Strike and Half-Life. Winner of over 25 2008 Awards - named Multiplayer Game of the Year by virtually every media outlet. 100's of Zombies. Four sprawling single player and co-op "Movie" campaigns. 4x4 Versus Mode - play as the "Boss Infected." Survival Mode - 1 to 4 person quick match play. Advanced artificial intelligence drives both friendly and unfriendly creatures to dynamically create intense single-player, co-op, and multiplayer experiences every time the game is played. Match making, stats, rankings, and awards system drive collaborative play Designer's Commentary mode allows gamers to go "behind the scenes" of the game. ESRB Rating: M - Mature Genre: Shooter Features: Addictive co...