Left 4 Dead (series)

Left 4 Dead
Series logo for Left 4 Dead
Genres	First-person shooter, Survival horror
Developers	Valve Corporation (2008–present) Valve South (2008–2009)
Publishers	Valve Corporation
Platform of origin	Microsoft Windows Xbox 360
First release	Left 4 Dead November 17, 2008
Latest release	Left 4 Dead 2 November 17, 2009

The Left 4 Dead franchise is based on a series of cooperative first-person shooter, survival horror video games developed by Valve Corporation. Set in the days after a pandemic outbreak of a viral strain transforming the majority of the population into zombie-like feral creatures, the games follow the adventures of four survivors attempting to reach safe houses and military rescue while fending off the attacking hordes.

The games encourage cooperative play between up to four players, each taking the role of one of the survivor characters and the computer controlling any unassigned characters. Players use a combination of melee weapons, firearms, and thrown objects to fend off attacks from the bulk of the infected creatures, while using an assortment of healing items to keep their group alive. Certain unique infected creatures pose a more difficult challenge, typically requiring teamwork to take down effectively. The games are overseen by an "AI Director", designed to give the players a more dramatic experience based on their performance, penalizing players for stalling while rewarding players with special weapons by taking longer or riskier paths. The Director also makes gameplay dynamic, meaning that no two playthroughs are quite the same.

The Left 4 Dead franchise games take place in the days following a pandemic outbreak of an infection that transforms humans into feral, zombie-like creatures, seeking to kill those yet to be infected. Within the United States, the Civil Emergency and Defense Agency (CEDA) orders the creation of safe zones with the aid of the military, and evacuates as many people as possible to these areas, aiming to transfer them to islands and ocean-going ships, as the infected are unable to cross bodies of water. A number of people are discovered to be immune to the infection, though they can carry and unintentionally spread it to others. In both games, four of these "Carriers" or otherwise just immune humans, meet and become the game's "Survivor" characters, making their way to safe houses and extraction points.

The Left 4 Dead games are first-person shooters incorporating survival horror elements. A player controls one of the four Survivor characters, and has the ability to move, jump, and use weapons in their possession. Players are limited to two weapons: a main firearm with limited ammunition taken from ammo caches, and either one (or two pistols) sidearm with unlimited ammunition or a melee weapon. Players also have three additional inventory slots. The third slot gives the player a thrown weapon, including a Molotov cocktail, a pipe bomb that can be used to lure a horde towards it before it explodes, or a bile jar that can be used to lure a horde to a specific area. The fourth slot provides for either a health kit which they can use on themselves or the other survivors, a defibrillator to revive a dead Survivor, or a special ammo deployment kit providing unique ammo such as explosive bullets. The fifth inventory slot is used for pain pills, giving the player a temporary health boost, or an adrenaline shot, temporarily increasing the player's speed. Some environmental objects like propane tanks or gasoline cans can be carried and thrown at hordes, upon which they can be fired upon as a makeshift explosive, but cannot be stored in the player's inventory. In Left 4 Dead 2, limited-use weapons such as the chainsaw or the machine gun can also be carried in a similar manner. The player can use whatever object they are holding to temporarily push back any Infected surrounding them.