Addictive co-op action gameplay from the makers of Counter-Strike and Half-Life
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
20 new maps. 10 new weapons. Four sprawling campaigns.
Match making, stats, rankings, and awards system drive collaborative play
Designer's Commentary mode allows gamers to go "behind the scenes" of the game.
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