IGN written quite a few previews on Valve's Left 4 Dead, explaining the core gameplay concepts and generally how everything works, so they'll try to trim out most of the basics for this one. Just in case you've been hibernating in the Arctic wastes for the past year or so, here's a quick refresher. Left 4 Dead is a cooperative first-person shooter that pits four players against hordes of zombies, called infected. Each stage is set up so the survivors must move from point A to point B while fending off waves of zombie attacks. As a twist, you can choose to play on the infected side, spawning as one of four types of boss zombies with special powers.