Left 4 Dead:  is an upcoming multiplayer co-operative survival horror FPS game by Turtle Rock Studios which is, as of January 10, 2008, part of Valve Corporation. The game has been built using Valve’s Source engine and will be available on PC and Xbox 360. Certain Affinity is responsible for the Xbox 360 version of the game. Left 4 Dead puts four human playable or AI controlled survivors of an apocalyptic pandemic against hordes of the Infected. Regular Infected are controlled by the game AI, while human players can control up to four mutated Boss Infected with special abilities. The goal of Left 4 Dead for the Survivors is to help each other make it through a level to safety. Infected players must cooperate to stop them.

The expected release date for Left 4 Dead is Q3 in 2008. The game was first revealed in the Christmas 2006 publication of PC Gamer UK with a six-page article describing a playthrough at Valve’s headquarters. The game was first playable at the Showdown 2007 LAN in San Jose and at QuakeCon 2007. A teaser for the game can be viewed in The Orange Box. If the main menu is kept on long enough it switches to a trailer first of the different aspects of The Orange Box, then a short teaser for Left 4 Dead is shown.

Setting and levels

There will be four scenarios, each with five maps or "acts," in the first release of Left 4 Dead. These scenarios take place in various urban and rural locales: a hospital, cornfield, airport, and murky countryside. Four players take control of the four main characters of the game, "The Survivors", who play through the levels fighting off the Infected, which are humans who have been infected with a mutated form of rabies. The first four acts of each scenario will have the players move from safehouse to safehouse, indicated by a red door, where the players get a save point and those who have died earlier in the level will return. The fifth act will have the players defending their position from a final onslaught of the infected until their getaway vehicle arrives, such as a helicopter in the hospital scenario. Each scenario lasts between 45 and 75 minutes

Damage, dying and checkpoints

Survivors don’t die instantly from too much damage — they are first knocked down, but can continue to fire with their pistols until helped by another Survivor or they bleed to death. The Survivors can be knocked down a maximum of three times, after which they are dead. Movement speed is affected by injuries, slowing damaged Survivors down until they are helped by health kits or pain medications. Checkpoints provide a respawn point for dead Survivors. As long as one Survivor manages to reach a checkpoint, the others will appear again on the map in closets or in other "trapped" situations, and will rejoin their allies when found. Left 4 Dead will have full friendly fire that can’t be switched off

Playing as the Infected

Four additional players can take control of the more powerful Boss Infected with unique abilities amongst the other AI Infected. Since only one Boomer, one smoker and two hunters can be played at any one time, players must select their preferred Infected and wait for it to spawn. Players can also control the Tank, but it’s only spawned a few times during each scenario. A special alert gives Infected players the option to start playing as the Tank when it does spawn.

The infected have the ability to see survivors through the walls at a certain range if the survivors are running, with the flashlight on, or talking. Otherwise, Survivors are not visible through walls. The Infected can also see in the dark, unlike the Survivors.

If a player playing an infected dies in less than about 3 seconds after spawning he/she is immediately respawned. Infected spawn in front of the Survivors and can, if they stay still, see a marker for their likely path of advance so they can set up ambushes.

Throughout levels, Infected-only ways up buildings are marked with symbols. These can be climbed and used for ambushes, especially with the Infected immunity to falling damage.

Team coordination and communication

The Survivors can communicate by automated voice commands that are accessed by quick menus. They will also sound off automatically when doing such things as reloading or spotting Infected. Over 1000 unique lines have been recorded for each Survivor.

The Xbox 360 version of the game will remove the quick key voice commands in favor of the Xbox Live headset.

Survivors will also be able to see each other through walls as colored outlines to make it easier to find each other.

AI

The AI in Left 4 Dead allows the game to be played by fewer than four players, by making the other survivors bots, these bots will follow one of the player-controlled survivors. The Infected bosses will also be played by the AI, if there are fewer than four players on the infected team. The AI in Left 4 Dead is claimed to be convincing enough that survivors won’t be able to distinguish between bots and real players in the role of the infected.

The Director

The AI also features a dynamic system for game drama, pacing and difficulty called the "director". Instead of fixed spawn points for enemies, the AI director places enemies in different positions, creating a new experience each time. It will also balance action and moments of tense calm When the AI Director feels that players have been facing a particularly intense battle it will slow down the tide of enemies. After a sufficient lull of action the director will send more enemies to increase the drama again.

Award system

Left 4 Dead will include Steam’s achievements system, which records players’ accomplishments and mishaps. There are different awards for the different "teams" in the game:

The Survivors

The Survivors receive merits for accomplishments such as completing a Scenario without using any health items or the flashlight. Survivors will also receive awards for doing things such as helping a downed survivor get back up, or by saving them from the infected.

The Survivors receive demerits for mishaps such as shooting a teammate, or killing a boomer near teammates. Survivors will also receive demerits for walking into friendly fire, or purposely causing one’s death without giving the rest of the survivors any benefit from it.

The Infected

The Infected receive merits for accomplishments such as killing a survivor, or poisoning a survivor. The Infected will also receive awards for helping other infected kill a survivor by making a combined attack on a survivor, or causing a swarm of infected to kill a survivor.

The Infected receive demerits for mishaps such as harming a teammate, or killing a teammate. The Infected will also receive demerits for walking into friendly fire, avoiding the survivors for a certain period of time, or purposely helping the survivors.

The Survivors

The survivors. Left to right: Louis, Francis, Zoey, Bill.

There are four playable human characters in the game, each with a different and unique appearance to make it easier to identify which character you are looking at when you aren’t close enough to recognize the face. Each player is randomly assigned a character when they join the server and each character has the same abilities and may use the same weapons Bill

A Vietnam veteran with combat skills that have helped keep him alive, he is also the eldest of the band of survivors.

Francis: The tattoo-covered biker. He knew Bill before the outbreak of infection as well, which may mean they both went to Vietnam, but is unlikely since Francis appears much younger than Bill.

Zoey: The teenage daughter of a wealthy family. Zoey’s face is modeled from Alésia Glidewell, the person from which Chell from Valve’s Portal was modeled.

Louis: An assistant manager at a local retail electronics chain store. Although there are only four playable characters, as you progress in the game players will encounter NPCs who will help you and your team out.

Weapons

The main weapons in Left 4 Dead are divided into two tiers. The first is available to everyone when the scenario starts. Weapons in the second tier can be found throughout the maps and at the end of the scenario, just before the final fight. All weapons can be used to bash Infected with in close combat, pushing them back. The weapons have been said to resemble those of Counter Strike: Source, but with increased recoil. There is no information on the amount of ammo that is given to the players when they acquire each of these guns, or if there is a way to distribute them to other teammates.

Main Weapons – First Tier

Each survivor has the choice of starting with one of either weapons, but they can switch or restock ammo on checkpoints.

• Pump shotgun deals heavy damage to an enemy or many at once. Holds 7 or 8 shells and can be shot without reloading all shells.
• Uzi submachine gun deals light progressive damage. Holds around 50 cartridges and has enough accuracy to shoot at medium range.

Main Weapons – Second Tier

Each survivor has the choice of switching their first tier weapons to one of these on later checkpoints.

• M16 Rifle in the game can be viewed as a more powerful and accurate version of the Uzi.
• M21 in the game is extremely powerful, is the most accurate, and is still mildly accurate without having to use the scope.
• Benelli M4 Super 90 semi-automatic shotgun in the game can be viewed as a more powerful version of the Shotgun that does not require a pump after each shot.

Secondary Weapons

Each survivor starts with a handgun, and they can be restocked on checkpoints.

• Handguns, apparently .45 caliber Springfield Armory 1911 pistols, is mainly used as a support or emergency weapon. If a second handgun is found, they can be dual-wielded. When a survivor is knocked down the only weapon that can be used is the handgun, but accuracy is greatly diminished in this state.

Tertiary Weapons

Each survivor has the choice of carrying only one Molotov Cocktail or Pipe bomb.

• Molotov Cocktail burns anything its fire touches and kills most infected that come into contact with it.
• Pipe bomb is extremely powerful and dangerous to use due to the size of its explosion and its ability to kill all survivors and infected nearby.

Other Weapons

During the hospital finale your team will be equipped with a machine gun. You will use it to fight off the two tanks that will be spawned during this time and to get rid of the horde. Also there will be a machine gun equipped on the helicopter you depart from so you will be able to shoot away at the infected while escaping.

The Infected

A part of the Infected horde in the hospital campaign.

The Infected are Left 4 Dead’s foe of the survivors, and they are partly inspired by the infected from the 2002 film 28 Days later The Infected, as opposed to the slow, shuffling types associated with Night of the Living Dead or Half-Life., are fast and can pounce, creating quite a formidable foe. They will however go down with a well-placed gunshot, meaning they can be dealt with easily on their own, but in great numbers are difficult to handle. In addition, there are five mutated Boss Infected who have their own special abilities and are more powerful than the regular Infected:

The Boomer

A hugely obese Infected that can projectile vomit at The Survivors, blinding them and attracting swarms of nearby Infected to them. When Boomers die they blow up, creating a large amount of damage and exorbitant amounts of gore and viscera, this also attracts NPC infected to the area in which the Boomer exploded. Boomers can also drop from tall buildings into/onto a group of survivors, and once they impact on the streets, they "pop" exploding in the aforementioned manner, this skill could serve as an effective method for ambushing the survivors.

The Hunter

An agile Infected who can climb walls and jump over rooftops, similar to 28 Days Later Infected and Half-Life 2’s Fast Zombie. If the Hunter crouches for a certain period of time, a meter will fill and it can use it’s most powerful attack (this was chosen instead of it becoming invisible once backed up to a wall or similar piece of cover, turning invisible, and then pouncing). It can then pounce on a survivor, pinning them down on the floor and slashing at them with its claws, rendering the victim powerless unless The Hunter is killed by a team-mate or knocked off its victim. It is extremely weak, and can only sustain minor gunfire before dying. The Hunter can also retreat, and slowly heal itself.

The Smoker

An Infected with a long, whip-like tongue that can drag Survivors away from their team-mates and use its tongue as an organic noose to strangle Survivors when it is perched on a rooftop. Similar to Half-Life’s Barnacle, or Resident Evl’s Licker. When in danger, it can leave a haze of black smoke, distorting the Survivors’ vision.

The Tank

A huge, muscular Infected capable of throwing large items such as cars or blocks of concrete. Its slow movement is countered by high strength and toughness. To prevent the tank from camping away from the survivors for too long a frustration timer is set when the survivors are not in sight. When the timer runs out the tank becomes uncontrollable and begins stomping and thrashing giving away its position and becoming vulnerable to the survivors.

The Witch

The only mutant infected that will not be available to players. They are passive upon discovery by the players, but react with hostility to flashlight beams, physical contact, and gunfire in the vicinity. It will be able to kill a player in one hit, and has almost as much health as a Tank, making them the most dangerous of the infected. She has the resemblance of average infected, but can be heard crying to give the players a chance to avoid or attack her. The witch will not be included on the easy difficulty.

GUI

HUD

The player’s HUD will allow them to see how much health, ammo, and equipment they have left. The players will also be able to see the name of their teammates, the picture of whom a teammate is playing as, the amount of health and equipment each of the other teammates have, as well as if they are in danger, downed, or dead.

Awareness

The game will feature full body awareness in which the players will be able to see their own bodies when they look down, a departure from previous Valve games where the player’s lower body is not visible. For example in Valve’s Half-Life you would look down and see nothing but floor, but in Left 4 Dead you will see your legs and other parts such as your torso and arms.