Turtle Rock Studios, the development house responsible for Counter-Strike: Condition Zero and Counter-Strike: Source is back with Left 4 Dead, a different take on the online shooter. It seems a virus has infected the majority of the game's inhabitants, except for a few who for whatever reason are immune. Those resistant Survivors must then battle their way through gangs of Infected to safety, using a variety of guns and explosives. Up to eight players can join a server to play, with four on the Survivor side and four playing as special Infected monstrosities. IGN recently had a chance to play it and get the details on exactly how this game works.