Left 4 Dead (L4D) is a new action title from Valve, creators of the Counter-Strike and Half-Life games, and promises to redefine the co-operative genre as those titles did for multiplayer and single player action games.

Set in a modern day survival-horror universe, the co-operative gameplay of L4D casts four "Survivors" in an epic struggle against hordes of swarming zombies and terrifying "Boss Infected" mutants.

Valve’s next generation AI technology, allows for games of 1 to 8 players. Players can play as a Survivor or as one of four types of "Boss Infected," each of whom possess a unique mutant ability such as a 50-foot tongue lasso or a giant belly full of explosive methane gas.

The gameplay takes place across four massive campaigns. The "zombie" population of each mission is choreographed by an "AI Director" that monitors the human players’ actions and creates a unique and dramatic experience for them on the fly.

Set in the immediate aftermath of the highly-anticipated zombie apocalypse, Left 4 Dead features single player, multiplayer and co-operative gameplay modes. Next-generation artificial intelligence tailors the pacing and difficulty ensuring a different experience every time the game is played.

Beginning Friday at 12:01 am GMT, the PC version of Left 4 Dead will be available for a free 24-hour trial via Steam. The free trial will include access to the recently released Survival Pack DLC, which introduces a new multiplayer game mode and two additional Versus campaigns. Those who wish to give L4D and the Survival Pack a try may now pre-load everything needed to play with no obligation to purchase.

The Left 4 Dead Survival Pack introduces a new multiplayer game mode entitled, Survival, plus two complete campaigns for Versus Mode . A Critic's Choice Edition of the game is also heading to retail stores this spring, and will include access to all the content introduced in the L4D: Survival Pack.

Survival Mode

- New gameplay Mode
- 16 maps including Last Stand
- Leaderboards
- 7 new achievements

Versus Changes

- Fixed a case where versus team score would continue to be recalculated after the score panel was displayed
- Fixed an issue with recalculating the versus score health bonus for a player when they are rescued from being incapacitated
- Fixed being able to start a swing as an infected, then teleport to the survivors and have the claw swing hit a survivor
- Fixed a case where teleporting to the survivors would not reset the ability timer
- Fixed an exploit where you could load the chamber of a weapon with bullets by holding down the melee key
- Fixed a case where it was not possible to join a game while it was in a finale
- Fixed a rare case where listen servers would speed up the game over time
- Removed convars related to melee fatigue
- Fixed a case where infected players would get a respawn time on their initial spawn into a map

Server Changes

- Made ms_force_dedicated_server not require cheats
- Add a message when queuing a heartbeat
- Simplified setting of game mode.
removed convars director_no_human_zombies and director_holdout_mode
added mp_gamemode [coop,versus,survival]

General

- Added lobby join and leave messages

System Requirements:

• OS: Windows Vista, XP or 2000
• CPU: 3.0 GHz P4, Dual Core 2.0 or AMD64X2 (or higher)
• RAM: 1 GB for XP / 2GB for Vista
• Disc drive: DVD-ROM Drive
• Hard drive: At least 7.5 GB of free space
• Video: Direct X 9 compatible video card (Video card must be 256 MB or more and should be a DirectX 9-compatible with support for pixel shader 2.0)
• Sound: Direct X9.0c compatible sound card

Left 4 Dead is currently available on PC and Xbox 360.