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.

Left 4 Dead has been updated with a host of fixes, tweaks and new features, including enhancements to Versus mode for improved competitive play. The full change list is below. For PC users the update will be applied automatically via Steam. Meanwhile, the update will be made available to Xbox 360 players in the coming weeks.

General

- Fixed Survivors being able to climb surfaces marked for versus infected only.
- Fixed a class of SurvivorBot bugs dealing with rescuing downed players.
- Players can no longer grab ladders while flying through the air after a Tank punch.
- Shooting near a car with an alarm that has already fired the alarm will no longer make chirping noises.
- Improved loading time.
- Fixed mini-gun physics exploit.
- Fixed propane tanks (and other physics objects) causing players to fall through elevators.
- Fixed rare achievement bug issues.
- Fixed several map exploits.
- Fixed various match making issues.
- Fixed NAT traversal issues.

Versus Changes

- Added HUD elements to show status of other infected players.
- Changed color of infected player name in chat to red.
- Fixed exploit where players could spawn infected bots
- Fixed instance where a Survivor changing to the infected team would be attacked by infected bots.
- Normalized special infected melee damage.
- Made the following client commands cheat protected: "Kill" and "explode".
- Fixed exploit where infected players could run away and teleport back to gain health.
- Players can only change teams once per map.
- Players can't change teams while other players are still loading.
- Tank spawns at the same % through the map for both teams in versus mode.
- Made the Tank and Witch spawn directly on the escape route.
- Increased chance of getting the Tank or Witch.
- Fixed team swap issue.

Hunter

- Easier to pounce a Survivor who is meleeing.
- Increased Minimum damage a Hunter pounce does.

Smoker

- Fixed Smoker tongue tolerance.
- Smoker now has to be killed or the tongue destroyed for the tongue to break.
- Survivor's cannot bash someone off the tongue until the Survivor being pulled is paralyzed or hanging
- Tongue attacks that fail to paralyze or hang a Survivor will use the shorter ability delay timer.
- Fixed cases where the ability timer was not using the correct time.
- Fixed case where you could point at a Survivor but not register a tongue hit
- Fixed Smoker tongue not targeting and landing properly through PZ ghosts.
- Smoker tongue does damage every second while dragging paralyzed Survivors.

Tank

- Bashable objects now appear with a red glow.
- Tanks hitting a car with an alarm disables the alarm permanently.
- Tank frustration timer is only reset by hitting Survivors with rocks or fists.
- Reduced autoshotgun damage against Tanks.

Witch

- Witch spawns at the same % through the map for both teams.
- Avoids spawning within a certain % of the tank.
- Fixed an exploit where the Witch could be woken up and tricked into attacking Survivors.

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 due for release on PC/Xbox 360 on Nov. 18 in North America and Nov. 21 in Europe. The worldwide Steam release will happen November 18.