Gameplay is divided into Survivor and Infected sides. Take your pick.

Survivors

To start off…
- Left 4 Dead is a First Person Shooter Co-operative Multiplayer game in which you can play as one of four people (called “Survivors”), luckily immune to a virus that’s sent most of the population raving mad. You, as a survivor, are pitched against a seemingly endless horde of infected humans, turned into deranged psychopaths, as a upshot of the lost battle against the virus.
- There are no character classes, every player starts off on an even footing in stipulations of skills and weaponry, meaning success requires teamwork and quick thinking.
- At the start of each campaign of choice you and your comrades start with a basic pistol. Next to you are tables from which you can grab your choice of SMG or shotgun. Then you get into the action.
- Friendly Fire is always on in all conundrum levels, and there is no way of turning it off.
- Your goal is simple…carry on. Reach the rescue zone at the end of the campaign.

The ‘Infected’
- Whilst players with 21st-century weapons pitted against weaponless psychopaths with no thought of tactics may seem like a no brainer, it won’t be. The infected have one very clear advantage…

…numbers. Massive numbers.
- The Infected horde is gigantic, they pour out from everywhere. A lack of strength means nothing if there are a excellent fifty or so of them attacking at once.
- One thing that needs to be stressed is the speed of the Infected. These aren’t half-dead shamblers, they are alive, mad, and their speed shows it.
- Usually you’ll find infected wandering around the city aimlessly. But once they see you, they’ll know you’re not one of them, and their demeanour changes immediately. Their only thought is of stomping your face in and, except you do something about it, that’s exactly what they’ll do.
- You cannot kill all of the infected. There is no set number of them. They attack you at the Director’s discretion, and they will not stop coming. The goal is to escape, there is no way you can carry on if you stay in one spot for too long.

Unfair Advantages
- As the survivors, you have access to a variety of projectile weapons and pleased small explosives. Shotguns, Uzis, and Pistols are all at your disposal from the get-go, with more weapons becoming available as the game progresses through the separate levels of the campaign (scroll down further for a more in-depth view of the weapons).
- Equipment-wise, you have a flashlight (boundless battery) for seeing in the dark, can see the outlines of your teammates through parapet and other objects so you don’t get separated, and have one med-kit each for healing physically or a teammate.
- There is a melee attack with your stick that does some minimal hurt, but its valuable aspect is that it pushes the infected back. Tactical uses of this become apparant with the knowledge that pushing one into another will cause both to fall down, and domino effects are quite in play. Also, the only way to successfully combat some of the Boss-Infected without hurting your teammates is to melee them away before to using the more deadly aspects of your chosen stick.
- As a Survivor, you can close doors behind you. This successfully stalls any infected pursuing you, for a while. They can and will break through wooden doors, but it takes a while, and it is also possible to blow a hole in it physically use it to shoot at them, though that only delays the inevitable. Of course, certain Boss-Infected don’t find doors very hard to open. Or parapet, for that matter.

‘Til death do us part…
- Death is being handled differently in Left 4 Dead, but note you will not get Infected if you die.
- As a replacement for of failing outright when your health reaches zero, a Survivor will fall to the earth and be unable to go, only having the energy to weakly fire their pistol.
- When you hit the dirt, a ‘bleed out’ timer commences. Pretty much your health is replaced by temporary health (300 points), which slowly depletes (at 3 health points per second), with any extra hurt from Infected (or careless teammates) depleting it quicker. When it is depleted, you die.
- Here, a mate can help. You can be ‘revived’ by your mates if they face you and press the appropriate key, causing them to pick you up and keep you going. Of course, this takes precious time and, when you’re bearing the burden of an infected horde, sometimes it’s wiser to deal with them first.
- You can only be revived three times. When you’ve used up all three of your revives, your view will become black and white and your health temporary. If you cop it huge time again, you will immediately die rather than simply being knocked down.
- When you die, you have to spectate until your teammates find another Survivor, either barricaded in a closet or at the next checkpoint, depending on where you died on the map. When you respawn after death, you start off again with basic equipment, wherever you are.
- The speed at which you go is affected by your health. 100% and you’re beating Cathy Freeman, 1% and you’re slower than a two-legged turtle with hemorrhoids. It’s valuable for healthy survivors to keep an eye on their injured comrades, as it can be all too simple to leave them behind to be simple pickings for Infected. It is in every Survivor’s best interest to keep everyone at full health, as the group can only go as quick as it’s slowest member.
- Each survivor will be able to carry one medkit, which can be used to patch physically or your mates up, it can only be replaced by finding one throughout the map or at the next checkpoint
- There are also pills, which give you a temporary health boost that depletes back to base health over time, but are very quick to take.

The Director
- You will not be wading through hordes of infected from start to end. What Valve has implemented is an AI Director that places the infected on the map in real time using no flags or checkpoints at all. It is intelligent enough to place them on it’s own, needing only a map to be able to work with.
- As a upshot every game is relatively unique to play through, as you will never know where and how many zombies are going to be hitting you at any certain time.
- The director also works on a system of highs and lows. There will be times you are fighting for your life, and there will be times where you don’t encounter an infected for a minute.
- There are a few tiny mini-stands scattered throughout a campaign, as well as the finale while waiting for the rescue vehicle, but apart from that, the Director is not scripted.

Communication
- In a co-op game, especially one such as this, communication is vital. Implemented into Left 4 Dead is a call system that involves pressing a corresponding key and moving your mouse in a direction on a radial menu of commands.
- Also, there is an implemented auto-alert system in which your character automatically says something when a certain event happens (ie ‘Help!’ when knocked down, or ‘Boomer!’ when the crosshairs are centred on a Boomer).
- There is over 1000 lines of dialogue for each character so generally there is a excellent variety of voice-acting available.
- On top of this is the ever present in-game chat, allowing communication between players with microphones.

Infected

Choosing the other side
- In Versus mode you can, if you want, choose to forgoe the weak realm of sanity and become an Infected psychopath, hellbent on killing the four survivors.
- This is entirely different from playing as a Survivor. Your goal is to terrorise and kill, to do your absolute best to hamper and harass the Survivors until they are overwhelmed.

It’s all in your head
- As a Boss Infected, your goal is the same as that of the infected horde, kill the Survivors before to they can escape.
- With hundreds of Infected at your side, it may seem an simple chore, but with the infected as weak as they are (they are only human, after all), you will not carry on, let alone hurt anything, by mindlessly charging in there.
- Tactics is the game here, you know when, where, and how you are going to attack. They don’t. This immediately gives you an advantage, and it is up to you to use that advantage to it’s fullest potential.

Boss Classes
- There are four playable types of Boss-Infected, renowned as the Boomer, the Hunter, the Smoker, and the Tank (scroll down for a more in-depth look at them). The first three are the most common, with the Director spawning you as them more often, while the latter is given out randomly at certain times due to it’s power.
- There are limits as to how many Boss Infected there can be at once as well as limits on each Boss infected (One Boomer at any one time etc.). The Director has full control over what Boss Infected you will spawn as.
- Everyone will get a opportunity to play as a Tank before to someone gets a opportunity to play him for the second time.
- Respawn times for the Boss Infected range from 15-20 seconds.
- All Boss Infected have a basic melee attack, it’s not a primary stick (exception the Tank), but it helps to dish out some pain before to you lose your head. Apart from this, the Boss Infected rely heavily on their special abilities to kill the Survivors. All the bosses special abilities are geared towards different types of play, and can all be devestating if used correctly. Scroll further down for a more in-depth look at the Boss Infected themselves.

Stickin’ it to ‘em
- Playing as the Infected is very different from the Survivor side. Most obviously when you take your position behind a pair of bloodied hands, you can see the outline of survivors as a ghostly map which can be used to see them at any time.
- There is an exception to this ‘Survivorvision’. If a Survivor is standing completely still, without their flashlight on and aren’t shooting, the red outline becomes nonexistant.
- So, Infected players can nearly always see where the group of survivors are thus they always have the element of surprise, being able to position themselves in many places Survivors can’t.
- Other advantages of being Infected is complete immunity to fall hurt, night thought, and having the ability to climb parts of parapet that aren’t available to Survivors. Thus the infected have a fantastic deal more of the map available to them, and are much more mobile, with the ability to attack from any angle.

The Director
- What you will first notice when the Director pops you into the map, is that you can choose exactly where you spawn, with the only limitation being that you can’t spawn within a pre-determined distance of the Survivors (or in their line of sight). Generally, the director will drop you where the Survivors currently are.
- What essentially happens is that you are place into the map as a ‘ghost’, then you run around, look at the surroundings, and choose physically a place to spawn. Then you go annoy the Survivors.
- The Director has full control over what Boss Infected you will spawn as. If you die, you are respawned after a small wait to continue toward your goal.
- By working with the Director (as in watching his use of the other infected) you can spin things to your advantage while attacking the Survivors, such as dropping into the midpoint of them from a rooftop as a Boomer when they are surrounded by infected. Or, if you are fortunate enough to find the Witch before to them, attack in a way as to herd them towards her.

Psychotic Tactics
- Apart from the Tank, playing as the infected tends to go towards ambushing. You want to attack when it’s the worst time for the Survivors, and generally this involves you stalking, waiting around a certain corner, then WHAM! You’ve frightened the poopers out of them and maybe even done some hurt.
- Generally, if you attack, don’t be surprised if you die, especially if you charge head-on. Infected are weak, even the Boss’, and attacking from a ambush will not guarantee you anything except you do it right. The whole goal is not to outright kill the survivors physically, but make enough mayhem in their ranks so they can get separated, overwhelmed, or just unadorned baffled enough so the horde can rip them to shreds. Sure you can kill them, and you should, a skilled and fortunate player can take all of the Survivors out in one go. But don’t run in there expecting to notch a kill every time.
- As for the Tank, you must do the complete contrary. You can be heard for miles, and if you don’t attack Survivors in a certain time, it’s the of poorer quality off for you. So basically you find them, and try to kill them.
- In that sense, the whole aim is whittle down the Survivors, chip away at them over time until they cannot stand the constant attacks, and then slaughter them.
- Playing Infected is for the most part very tactical. You have to choose the right second, the right place, and the right way to attack, otherwise you won’t do anything worth noting.

Other

Gameplay Modes and the Campaign
- There are two gameplay modes currently in Left 4 Dead. A Co-op Survival mode and another mode called Versus. ‘Survival’ is Co-op only, with no Human controlled Infected at all, while ‘Versus’ allows players to control the Boss-Infected as well.
- Nevertheless, in both modes, the Survivor’s must escape their quandary by getting to a point where an escape vehicle can pick them up. As the Infected (if the mode allows it), you have to stop them.
- There are four campaigns, consisting of 5 maps each, which can be both played offline (with AI controlled friends and enemies) or online with up to 8 players (four Survivors and four Boss Infected). They are seperated by the aforementioned ‘checkpoints’ in which you restock on ammo and health, and dead teammates revive if they were killed towards the end of a map.
- At the second it seems each campaign can take up to an hour to end (you can leave the game anytime you want, you’ll just be replaced by a bot until someone else joins)
- At each checkpoint a message will pop up showing how everyone did comparatively in certain areas (hurt to/as Tank, least hurt taken, Infected killed, etc.).
- At the end of each campaign, there will be an elaborate “last stand” in which you and your mates must hold off wave upon wave of Infected waiting for the rescue vehicle to come and rescue you. The Infected will temporarily stop attacking you so you can set up your defence, then you radio the rescue vehicle, a timer pops up, and all goes to hell. This is especially hard and you will be facing many more opponents than you did on foot to the point.

Regular Infected
Humans that have been infected with a type of rabies, these are successfully enraged psychopaths. They are grossly disfigured as a upshot of the disease, and attack uninfected persons on sight. It is unknown why they don’t attack one another all the time (though you can see some boxing from time to time).
Male Infected
The Horde

Boomers (1 allowed at any single second in time)
This is a form of Boss Infected who is grossly overweight, carrying a massive stomache full of bile and methane gas. He can vomit the bile all over a player, or several if he’s excellent, obscuring their view, and attracting all the surrounding zombies in the vicinity to attack said player(s), while also spawning some infected to help lower their life expectancy. Vomited-on Survivors are partially blind, and have all the infected (plus the spawned infected) in the area gunning for them. They are nearly completely helpless and must rely on their teammates to carry on.
On top of this, this guy will explode with tremendous force when shot due to the methane, so keep your distance. The explosion, while not doing any health hurt, will throw the aforementioned bile on any unsuspecting Survivor who is too close to the Boomer when it goes off, as well as staggering any Survivors in the pressing vicinity. This renders them unable to do anything for a small time, giving the Infected precious time to close in and do some hurt. It is quite possible to spell certain doom for the group by shooting this bloke at the incorrect time.
Suicidal Boomers can even jump off buildings and explode on impact, generally becoming a guided bomb in the right hands. Of the three most common bosses, the Boomer is the only one really equipped for tackling more than one survivor well. Of course, this is offsetted by his slow waddle, and the fact that you’d have to be blind, drunk, and facing in the contrary direction to miss the massive bugger.
The Boomer

Smokers (1 allowed at any single second in time)
Another form of Boss Infected, the Smoker’s specialty is his 50-foot tongue, which he uses to grab players from a fantastic distance (50 feet ). The tongue can be used to pull them into a mob of infected, or off a ledge to hang them, or just let them fall. Grabbed Survivors have a very small window in which to shoot the Smoker, but after that’s passed, they’re helpless. When ensnared by a Smoker, a Survivor will be pulled until they are at the Smoker’s feet, hanging off a ledge, or in a spot where they can’t be pulled further. In all of these cases, the Survivor will start taking hurt.
Like Boomers, this bloke explodes when killed, but as a replacement for of force this guy expels smoke when in his death throes. Very thick smoke, you can’t see in this stuff. Even the green outlines are hidden by this smoke, and Survivors start choking and can’t use voice communication.
The Smoker

Hunters (1-3 allowed at any single second in time)
The last selectable Boss Infected, Hunters are the assassins of the infected. They have two types of attacks, the basic punch and scrape, and Pouncing.
‘Pouncing’ is accomplished when a Hunter lunges after being crouched for a period of time, which sees it jump in an arc and land on a Survivor, pinning them down and shredding them to pieces except dealt with by his mates. The pounce can only be accomplished after it ‘charges’, which is done while the Hunter is crouched. When the pounce is fully charged but, the Hunter lets out a low growl, which can easily alert the Survivors if too close, so you must use it as soon as they’re in range if you want the element of surprise.
Hunters are hands-down the most mobile infected of the lot, which is accentuated by their incredible jump distances and attacks based on those jumps. Hunters can also rekindle health over time, giving them the ability to do several hit-and-run attacks. This is offsetted by the fact that the Hunter’s attacks are limited to only one target at a time, and demand it to really get into the fray in the midpoint of a group of survivors, which isn’t a excellent way to carry on in the first place.
Hunter

Tanks (1 allowed at any single second in time)
The largest Boss Infected, this bloke’s name is self explanatory. This bloke is a rock, a gigantic lump of muscle and sinew, insanely strong and quick enough to run any survivor down, but no stealthy options available to him at all. The track of this mother can be heard from miles away, so don’t expect to catch anyone by surprise.
Because the Tank is so powerful, it isn’t possible to choose to be him when playing as Infected. As a replacement for, a random player will be informed that he can be respawned as a Tank at the Director’s discretion. A Tank’s role is pure and simple, ruin with no thought of self-preservation and with one object in mind, the death of the Survivors. Locked doors and even certain parts of parapet will not stop your rampant destruction, so Survivors can’t simply lock themselves in a room and wait you out.
To stop Tank players camping for surprise attacks there’s a frustration meter that fills when you’re out of sight of the Survivors. When this fills, you lose all control of the Tank.
Nevertheless, this bloke can wipe out the Survivors if they aren’t skilled and use teamplay.
Tank

Witches (1 or two per campaign)
These are computer controlled Boss-Infected, and aren’t available to choose for an Infected player. That is because these are potentially the most perilous enemies in the game, and only appear once in a campaign.
A Witch spends her time writhing on the floor in agony. She won’t even take any notice of you except you do something asinine, such as walk too close to her, shoot near her, shoot her, or shine the flashlight at her. This lets you pass by her if you’re silent, which is the safer option.
If you do accidentally annoy her, or choose to risk attacking her, she’ll attack you. She is quick, she is strong, she kills with each hit. Try to dodge her if you can.
The Witch

**The above in rank was originally provided by General Balls on the Official Steam Forums.**