Left 4 Dead is a survival action game from Valve that blends the social entertainment experience of multiplayer games such as Counter-Strike and Team Fortress with the dramatic, narrative experience made popular in single player action game classics such as the Half-Life series of games.

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.
 
"...addictive and atmospheric, and it contains undoubtedly the best co-op gameplay we've seen yet." DarkZero
"One of the finest zombie games ever made, and one of the finest co-op games ever made." IGN
"...the next best thing to a real-life zombie apocalypse with fun and excitement in abundance." MEGamers
"A redefining moment for the survival-horror genre." The Onion A.V. Club
"...a fun and replayable co-op experience...Refreshingly original and polished..." YouGamers