Left 4 Dead is a multiplayer co-op surival horror game being published by Turtle Rock Studios in close partnership with Valve software, to be released before the end of 2007. The premise behind the game is that the rabies virus has mutated into a new, more virulent strain and caused a pandemic outbreak, infecting most of the world’s population. You and three other players are the “lucky” few who are immune to the virus. The rest of the world has been turned into mobs of bloodthirsty murderers, hellbent on killing you on sight.
These mindless killers aren’t your traditional shambling zombies however – they’re not even undead, instead very much alive and just as easily killed as a normal person. They are very fast however, and semi-intelligent when it comes to their attacks. Think 28 days later type of zombies.
A game consists of 8 player slots, 4 survivors and 4 boss infected (which we’ll cover in a moment). The survivors play out like your traditional FPS; they’re armed to the teeth, but must work together in order to advance. Rambos will quickly meet with an untimely demise, and failure to cover all potential angles of attack will be costly to the party. At the beginning of the game, the four survivors appear in a sort of safe area, where they can gather weapons, health packs, and explosives. When ready, survivors head out with the intention of reaching an evacuation area to be helicopter-lifted to safety. Standing between them are hordes upon hordes of infected, and the boss infected players.
Besides playing out like a traditional fps, there’s also some subtle nuances to playing as a survivor. Each player can grab a medpack, useful for restoring the health of either your teammate or yourself and staying in the game. Occasionally a survivor may get knocked to the floor and start to “bleed out”. When this happens, the remaining teammates have a limited amount of time to clear out the zombies beating on the player, and then help them get up. While bleeding out, players are limited to just the use of their pistols.
Should a player die, the game is not necessarily over for them. A player can be revived either at the end of a map in the next safe room, or teammates may occasionally come across their lost comrade hiding away in a closet or locked room further along in the level.
Campaigns are composed of five maps, and will take approximately an hour to finish. So far Turtle Rock Studios has shown one entire campaign publicly consisting of a romp through a hospital, subway, and building complex. The atmosphere is varied throughout, but most locales tend to be very dark and atmospheric.
In what might be considered the most revolutionary aspect of Left 4 Dead, zombies aren’t spawned from spawn points like a traditional FPS, instead Turtle Rock Studios has implemented a system called the Director. What the Director does is monitor the stress levels of each individual player and reacts accordingly – pummeling players with waves of zombies after a lull, then toning it down a notch, letting things settle, then ramping it back up again. What you get is a series of peaks and valleys in the action and games which are completely different each time, keeping the players guessing.
The Director also manages the in-game music, playing soft and creepy music when there’s a lull in the action, and ramping it up when the infected horde attacks.
The Boss Infected
The other 4 players in the game can opt to play on the infected side. This gives them access to four special infected, each with their own talents and abilities. Boss infected are very fragile, and can be taken down in a matter of seconds (with the exception of the tank boss) to focus fire. As such, your primary goal as a boss infected should be to attack the survivors at the most opportune times (mobbed by regular infected, separated, etc.).
This fat sack of methane has the ability to projectile vomit up a concoction of blood and bile which serves as zombie heroin. Upon landing on a survivor, all infected in the immediate area (plus some spawned adds) will swarm said player. With their vision hindered by the blood, it’s up to the remaining teammates to cover the puked upon, and make sure they don’t get overwhelmed. When killed, the boomer explodes in a blast of methane which harms all survivors near to him, so make sure to kill this one at range.
The smoker’s special abilities include releasing a cloud of smoke that obscures the survivors’ vision, plus a prehensile tongue the smoker can use to grasp a survivor around the neck and drag them over to him, hanging the player on the edges of building and debris, or just separating the player from his teammates.
The hunter is the stealth/agility unit. Able to leap 50 feet up in the air, pounce upon unsuspecting survivors, and even go invisible when standing still, the hunter is a master of hit and run. It’s also paper-thin, so as mentioned, players must remember to only attack at the most opportune of moments. The pounce attack is particularly vicious, it’s very frightening to have something suddenly scream at you, pin you to the floor, and start wailing on you with open fists.
This walking hulk can not be voluntarily chosen by players, instead the Director will randomly choose a player to assume the role of the tank periodically throughout the campaign. This beefy monstrosity takes a bit more concentrated firepower to take down than the other infected. The catch however is that you can’t bide your time and sneak up on the survivors with this one; he has an aggression meter which slowly starts building up for as long as he’s not within sight of the survivors. He makes a huge amount of noise as he approaches (making any form of stealth impossible), so this one is your “run in guns a’ blazing” kill machine.
The 5th type of boss infected is not playable, but instead makes appearances sporadically throughout levels. The witch looks like a normal infected, but is typically found screaming and writhing in pain on the floor. Capable of one-shotting players and laying waste to your whole party in a matter of seconds, the trick is to avoid her completely – the players must turn off their flashlights and tiptoe silently past her in order to avoid confrontation. If she turns on you however, the players must down her ASAP or risk a whooping.
Setting & Levels
Gameplay takes place in urban cities, small hamlets, wooded rural settings, shopping malls and other such locations. Four players take control of the four main characters of the game, “The Survivors”, who subsequently play through the levels fighting off the Infected, which are humans who have been infected with a mutated form of rabies. Each level has the players fighting towards a goal, such as escaping by helicopter. (The helicopter has to be called in by radio. During the final wait for rescue, players must face a final onslaught of the infected.) 
There will be four scenarios with around five maps each in the first release of Left 4 Dead.
Damage, Dying & Checkpoints
Check points also provide a re-spawn point for downed Survivors. As long as one Survivor manages to reach a check point, the others will appear again on the map in closets or in other “trapped” situations. Survivors don’t die instantly from too much damage, however. They are first knocked down, but can continue to fire with their pistols until helped by another Survivor. Movement speed is affected by injuries, slowing damaged Survivors down until they are helped by health kits or pain medications. Left 4 Dead will have full friendly fire that can’t be switched off. This keeps the challenge of the game up. 
Playing as the Infected
Four subsequent players can join the server and take control of the larger, more powerful Infected with unique abilities amongst the other AI Infected. Since only one Boomer, one Smoker and two Hunters are allowed at any one time, players have to 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 & 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. 
Survivors will also be able to see each other through walls as colored outlines to make it easier to find each other.
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 is less then four players on the infected team. The AI in Left 4 Dead is allegedly so convincing that survivors won’t be able to distinguish between bots and real players in the role of the infected.
The AI also features a dynamic system for game drama, pacing and difficulty called the “director”. Instead of fixed spawn points for enemies, the director AI 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.
Left 4 Dead will include Steam’s in-development awards system, which records players’ accomplishments and mishaps. There are different awards for the different “teams” in the game:
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 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. Left to right: Francis, Zoey, Bill, Louis.
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, to prevent arguments, each character has the same abilities and may use the same weapons.
- Francis Barrels
- The tattoo-covered biker.
- Zoey Coen
- The teenage daughter of a wealthy family.
- Bill Calhoun
- A Vietnam veteran with combat skills that have helped keep him alive.
- Louis Parker
- An assistant manager at a local retail electronics chain store.
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, as well as if there is a way to distribute them to other team mates.
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 30 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.
- Sniper Rifle in the game is extremely powerful, is the most accurate, and is still mildly accurate without having to use the scope.
- 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.
Each survivor starts with a handgun, and they can be restocked on checkpoints.
- Handgun 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.
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 Extremely powerful and dangerous to use due to the size of its explosion and its ability to kill all survivors nearby.
The Infected are Left 4 Dead’s name for what are essentially zombies. The zombies in the game are based on the zombies (who are ordinary civilians that are infected with a form of rabies, making them ravenous and psychotic) from the 2002 film 28 Days Later, which the game takes a lot from design-wise. The zombies, 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 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.
- The Hunter
- An agile Infected who can climb walls and jump over rooftops, similar to Half-Life 2′s Fast Zombie. If the Hunter stands motionless against a wall it will turn invisible. 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
- A zombie 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 from a rooftop. Similar to Half-Life’s Barnacle, or Resident Evil’s Licker. When in danger, it can leave a haze of black smoke, distorting the Survivors’ vision.
- The Tank
- A huge, muscular zombie 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, and can be heard crying to give the players a chance to avoid or attack her.
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.
The game will feature full body awareness in which the players will be able to see their own bodies when they look down. This is very useful for players when they are in areas where they want to be close to an edge, when they are downed they will know where their body is facing, and will help player hide themselves.