Left 4 Dead

Left 4 Dead is a first-person shooter in which the player takes control of one of four survivors; if human players are not available, the remaining survivors are filled by AI-controlled bots. They play through campaigns fighting off the infected—living humans who have been infected with a rabies-like virus that causes psychosis. The overarching goal is not to clear infected, but only to reach the next safe area alive. This is compounded by the presence of an "AI Director", who tracks each player's current situation, and will add or remove items and infected in response; with the goal of maintaining constant tension and creating a new experience with each playthrough. While a shooter, the game focuses largely on cooperation and teamwork, and thus eschews some "realism" conventions usual in other FPS games. Colored outlines of teammates are visible through walls to help players stick together and coordinate their movement. If a survivor's health is depleted, they become incapacitated and can only be helped by another survivor, after which they continue playing with lower health. If they are incapacitated twice without healing, the third incapacitation will kill them. During "Campaign" mode, if a survivor is killed, they will eventually respawn in a closet or small room, but must be freed by another survivor to rejoin the team. The AI will not open "respawn closets", so if all human player survivors are incapacitated, the level will restart. Survivors can share first-aid kits and pain pills, and heal each other. Left 4 Dead has friendly fire, increasing the need for caution and coordination around other survivors. Via a quick menu, the survivors can communicate and organize with voice commands and callouts. Over 1,000 unique lines were recorded for each survivor. Some levels are broken up with "crescendo events", which introduce a new obstacle before the survivors can continue moving. In the final chapter of each campaign, the players must defend a position from an onslaught of infected until rescue arrives. Each campaign typically lasts between 20 and 75 minutes depending on the difficulty level. Both platform versions of the game utilize an achievement system. Weapons Each player starts the game with a semiautomatic pistol, an M1911. It is the only weapon with unlimited ammo, and the only weapon that can be used while incapacitated. (If a second pistol is found, the player can dual wield them.) At the beginning of each campaign, survivors can choose between a submachine gun and a pump-action shotgun. As the survivors progress through a campaign, more powerful weapons can be found; the full-auto assault rifle, a semi-automatic shotgun, and a scoped hunting rifle. In addition to firearms, a player can carry three other items: improvised grenades (either a Molotov cocktail, or a pipe bomb with a smoke alarm, designed to attract the infected); are the enemies of Left 4 Dead, and comparisons have been made with 'zombies' from certain modern films, such as Dawn of the Dead, 28 Days Later, and Quarantine. An important distinction from the former is that the infected are, as cited in the game's manual, living humans infected with a rabies-like pathogen; more similar to the latter two films, rather than undead zombies. While they are never seen eating humans, bite wounds and mutilation are often mentioned. In an interview with 1Up.com, designer Mike Booth commented on the concept of using a pathogen as an inspiration for the setting: The "common infected" are fast and agile, weak individually, but overwhelming in numbers. They display a special attraction to high-pitched sounds, such as car alarms and the beeping device attached to pipe bombs. They will often chase down these noises while ignoring lower-pitched, louder sounds, such as gunfire. They occasionally attack en masse, referred to as a "horde". There are five "special" or "boss" infected, whose mutations grant them special attacks. Each of the special infected have a distinctive sound, silhouette, and musical cue, making their presence easily recognizable by players. There are five special infected in Left 4 Dead: In addition to the AI Director, there is a second Director that controls music. It was created as a way to keep the soundtrack interesting throughout the game. The music Director monitors what a player has experienced to create an appropriate mix. The process is client-side and done by a multi-track system. Each player hears their own mix, which is being generated as they play through the game; dead spectators will hear their teammates' mix. A far simpler version of the A.I. Director was previously used for some key battles in Half-Life 2: Episode Two. Valve is looking for ways to apply the Director in their future games to make pacing and difficulty more dynamic. Game modes Left 4 Dead contains four game modes: Campaign, Versus, Survival, and Single-Player. Campaign consists of up to four human-controlled survivors who attempt to make their way between safe rooms and eventually to rescue. In this mode, the special infected are controlled by the AI. In Versus, there are two teams of four players each. They play each chapter as both Survivors and Infected, swapping sides after each round. The victor is decided by which team scores the highest during the campaign. Survival mode consists of a timed challenge where players try to survive as long as possible against a never-ending flood of the infected, added in April 2009 in the Survival Pack DLC. ==Plot==