WorthPlaying writes: "Left 4 Dead takes place in a postapocalyptic zombie future, where four survivors are trying to fight their way through zombie-infested environments. Up to four players will guide these characters in either online or local cooperative multiplayer and complete a primary team objective for each map. The intuitive AI controls the enemies and your teammates, and the title utilizes a new technology, "The AI Director," which ensures that no two played games will be exactly the same. As players progress through a level, the AI will call for new enemies, sounds, and action to adapt to the team's performance. In short, skilled players will face more swarms of enemies than usual, whereas novice players will encounter toned-down difficulty."