Unlike most other shooters, Left 4 Dead hinges on cooperative multiplayer. You and three friends must shoot, tear and slash through an unrelenting mass of raging zombies. From the moment you leave the safe house to the final rescue chopper, you are completely dependent on each other and constantly hunted by special boss zombies that behave with their own aggressive, strategizing intelligence. Thanks to Valve’s omniscient “AI Director,” the zombies spawn differently every time, the special infected try alternative attacks, and even weapon drops are changed based on your performance. This makes every single playthrough slightly different, and the resultant strategy to survive much more organic and integral than any other FPS on the market. Just like Street Fighter is much more than mashing on buttons, Left 4 Dead is far more than mindless shooting. Played properly, L4D offers 100+ hours of unrivaled co-op insanity.