Gameplay Modes

There are currently 4 Gameplay Modes in Left 4 Dead, and 8 Gameplay Modes in Left 4 Dead 2.

Campaign

 * Play through a co-operative campaign online.
 * Available in Left 4 Dead and Left 4 Dead 2

During Campaign, also known as Co-op, up to four players work together to try to reach the end of the campaign by fighting their way past large numbers of AI-controlled Infected. There are four difficulty levels: easy, normal, advanced and expert. Each chapter ends in a Safe Room, a checkpoint triggered when all living Survivors, once inside, close the door behind them.

In Campaign mode, one or more players play as the Survivors, with the rest of the four filled in with AI-controlled "bots". The Survivors play through each chapter, making their way from safe room to safe room. The last stage in each campaign has an expanded ending called the Finale, which usually ends with players escaping with vehicles like cars, helicopters, etc.

Single Player

 * Play a single player offline game with computer-controlled teammates.
 * Available in Left 4 Dead and Left 4 Dead 2

Single Player is a gameplay mode with only one player controlled character. The player assumes control of one of the Survivors, and all the other characters are AI controlled. No other player can join a Single Player game. Other than that, the same rules as Campaign apply here, except for in Dead Center, or The Passing where you only have to get 8 (10 in The Passing) Gas cans instead of the 13 (16 in The Passing) you would normally have to retrieve in Campaign mode online.

Single Player is the only mode which can be played with Steam set to offline.

Split Screen
In Split Screen, two players on the same console take control over two Survivors, and the screen is split vertically, although it can be changed to horizontal in the options menu. The two players can also play online while using split screen.

This game mode is normally exclusive to the Xbox 360 version of Left 4 Dead and Left 4 Dead 2, but may be accessed in the PC versions if you have a controller for the second player and modify some files. Here is a guide to how to play splitscreen on the PC. Plugging the Xbox controller in and out during the loading screen is NOT the only way to set the Xbox controller to player 2. During gameplay, you can also unplug and plug the Xbox controller back in within one second to set the controller to player 2. In fact, the second method proves to be more effective with several people. On Left 4 Dead and Left 4 Dead 2, only one of the two players playing splitscreen on one Xbox 360 console while online has to have an Xbox Live account with gold membership; the other player can sign in as a "Guest".

Survival

 * Play Survival mode and hold out for as long as you can.
 * Available in Left 4 Dead and Left 4 Dead 2

Survival was released in the "Survival Pack," which came out on April 21st, 2009. The point of Survival Mode is to hold out for the longest time, with times being saved and virtual medals being awarded for surviving for certain amounts of time. Left 4 Dead features sixteen maps, fifteen of which are taken from existing campaign levels, and one new map which has been called The Last Stand. The campaign levels have been edited to remove things such as closets and other small choke points often exploited by the Survivors in crescendo events and finales.

In Left 4 Dead 2, Survival Mode is back, this time included with the release of the game. The point is still the same, and the maps are still converted crescendo events apart from The Motel from Dark Carnival's The Highway and Burger Tank from Hard Rain's The Milltown among others.

Versus

 * Play as the Survivors or the Infected in an online Versus Mode game.
 * Available in Left 4 Dead and Left 4 Dead 2

Versus is the basic competitive mode for the Left 4 Dead series: two separate teams of four players take turns playing as the Survivors and the Infected competing for the most points. In Left 4 Dead, points are only awarded to teams playing as the survivors. Points are calculated by the amount of health left in each player and how far the team got; however in Left 4 Dead 2, points are still only awarded to the survivors but no longer use the amount of health left in each survivor in the score, instead of just seeing how far each survivor got before they died (Unless they made it to the safe room). The points possible for the chapter is the same for both teams. Should both teams make it to the safe room, then the Tie Breaker calculates how much damage each team did to the opposing team, awarding 25 points to the winner. Before a game starts the lobby leader chooses a specific campaign to play and the players can choose which team to play on by choosing whether to start as infected or survivors. For help as Infected or Survivors, review some tactics.

Realism Versus

 * You can't see each other, but they can see you.
 * Available in Left 4 Dead 2

Realism Versus is a game mode that combines Versus and Realism. It was the first Mutation to be released for Left 4 Dead 2, but due to positive feedback from the community, was made an official game mode as of May 21st, 2010.

Realism Versus follows the normal rules of Versus mode in terms of gameplay style and scoring, but makes things harder for the Survivors as they are bound to Realism rules, such as lack of Survivor glows, or the Witch being able to instantly kill Survivors. Though Realism Versus will appear in the main menu, you cannot play it unless you have downloaded The Passing.

Realism

 * In a REAL apocalypse, good teamwork is all you'll have left.
 * Available in Left 4 Dead 2

Realism can be played on any difficulty setting. This mode removes the auras usually shown around players through walls. Also, the auras around items are only visible within a few feet, making the game require more communication and teamwork. Realism mode also makes bodyshots less effective as Common Infected can take more damage. The only weapon that can kill regardless where it hits is the M60 (wherein it causes body parts to explode) and the Magnum Pistol. Rescue closets are removed, making the defibrillator the only way to revive dead Survivors out in the open until you reach the safehouse, where they will respawn again. Witches kill instantly on any difficulty (with the exception of Easy or against an incapacitated survivor) and are notably harder to cr0wn. Speech bubbles over the Survivors are disabled when speaking via the microphone, although the speech bubble still appear above the character's icon. Unless one has an eye on the icons, knowing who speaks and spotting a talking teammate can be tough. Overall, this gameplay mode was created to take the teamwork factor that made the Left 4 Dead series famous to the next level.

Scavenge

 * Play as the Survivors or the Infected in a round-based competitive match.
 * Available in Left 4 Dead 2

Scavenge is a competitive gameplay mode in Left 4 Dead 2. It is a round based game in which Survivors have a limited amount of time to find up to 16 gas cans to fuel up a generator (or car), while fighting against player-controlled Special Infected much like in a Versus game. After all the survivors are incapacitated or the time runs out, the teams switch sides. Which ever team collects most gas cans wins a round and which ever team wins the most rounds wins the game.

Mutations

 * Available in Left 4 Dead 2

Mutations are tweaks and changes to the normal game rules. They can be for any game mode, which will be introduced each week by Valve on the in-game blog. Details for the next Mutation are revealed on at the same time the Mutation is released on Friday, via the blogs. On regular intervals Valve initiates a "Favorite Mutation" survey, and winners are put back into the cycle.

Mutations used in order are as follows:
 * Realism Versus: Realism Mode combined with Versus Mode. Realism Versus was made into its own gameplay mode permanently on the 21st May 2010.
 * Bleed Out: Campaign Mode, where only Adrenaline and Pills can be used to restore health. Survivors start with 99 temporary (and 1 permanent) health that decays over time. The Survivors must also face more regular hordes.
 * Follow the Liter: Scavenge Mode, where only one Gas can (or group of Gas cans) spawn at a time, forcing Survivors to go into a particular location. This also, however, lets the Infected know which direction the Survivors will have to go.
 * The Last Gnome on Earth: Campaign Mode, where the Survivors spawn with Gnome Chompski, which they must transport by carrying it all the way to the finale. The Common Infected will chase the Survivor carrying the gnome.
 * Last Man on Earth: Single Player, in which there are no Survivor Bots or Common Infected. There is just you and the Special Infected standing in your way to the safe rooms and rescue vehicle. Tier 2 weapons appear much earlier than normal and healing Items such as Pills and First aid kit are more abundant. If pinned by a Special Infected, you will revive in monochrome mode with next knockdown resulting in death unless a healthpack is used.
 * Chainsaw Massacre: Campaign Mode, where the Survivors start with only their Pistol. Chainsaws with unlimited fuel are on the ground at the start of each level. Other weapons will not appear throughout the campaign, but you can pick up another Survivor's discarded Pistol to use or dual-wield it with your own. Common Infected are generally spawned more early at the start of each stage.
 * Room for One: Campaign Mode Finales, where there is only room for one Survivor in the rescue vehicle. Once the rescue vehicle is active or the path to the vehicle opens, the first Survivor to the rescue vehicle wins.
 * Headshot!: Campaign Mode, where only headshots will kill Common Infected. Melee weapons require a headshot attack in order to kill Common Infected as well.