Gameplay Modes

There are 5 Gameplay Modes in Left 4 Dead, and 7 Gameplay Modes in Left 4 Dead 2.

Campaign

 * Play through a co-operative campaign online.

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.

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 exclusive to the Xbox 360 version of Left 4 Dead, but may be accessed in the PC version 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 membourship, the other player can sign in as a "Guest"

Versus

 * Play as the Survivors or the Infected in an online Versus Mode game.

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.

Survival

 * Play Survival mode and hold out for as long as you can.

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.

Scavenge

 * Play as the Survivors or the Infected in a round-based competitive match.

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.

Realism

 * In a REAL apocalypse, good teamwork is all you'll have left.

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. Rescue closets are removed, making the defibrillator the only way to revive dead Survivors. Witches kill instantly on any difficulty (with the exception of Easy) 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.

Mutations


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 "Favourite 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.
 * Bleed Out: A game mode based on Campaign Mode where only Adrenaline and Pills can be used to restore health. Survivors start with 100 temporary health that goes away over time. The Survivors must also face more regular hordes. In addition, pills will restore a players 'color' if a player goes 'black and white'.
 * Follow the Liter: This is a scavange variant, where only one gas can (or group of gas cans) spawns at a time, forcing Survivors to go after certain cans/groups of cans. This also lets the Infected know which direction the Survivors will have to go.
 * The Last Gnome on Earth: