Set in the immediate aftermath of the long-awaited zombie apocalypse, L4D's single-player and co-op game modes are played out across four sprawling "Movies" set in a variety of urban and rural environments. Each "Movie" has an over-riding team objective, is comprised of five large maps, and may be played by 1 to 4 human players. New technology dubbed the "AI Director" is used to procedurally generate a different experience each time the game is played. Just as in Hollywood films, the Director calls for new monsters, sounds, and action as it tailors the gameplay experience based upon the team's performance. In Left 4 Dead's Vs. Mode players may play as a Survivor or as one of four types of "Boss Infected." Each of the "Boss Infected" possesses an exceptional mutant ability - such as a 50-foot tongue lasso (Smoker) or a giant belly full of explosive methane gas (Boomer) - instead of traditional firearms.

Left 4 Dead: Survival Pack
The Left 4 Dead: Survival Pack is a collection of new content for 2008's Multiplayer Game of the Year. Headlining the pack is the new 1 to 4 person game mode, Survival, that challenges players and teams to "survive" unremitting swarms of zombies on over 10 maps. Rounds are scored by length of survival, and times will be uploaded to leader boards. Also included in the Survival Pack are two additional Versus campaigns. Each campaign features 5 maps for additional play of the four-on-four multiplayer game that allows players to compete as Boss Zombies versus the Human Survivors.