Left 4 Dead is a cooperative first-person shooter video game. It was developed by Turtle Rock Studios, which was purchased by Valve Corporation during development. The game uses Valve's proprietary Source engine, and is available for Windows and the Xbox 360. Development on the game was completed on November 13, 2008 and was released digitally on November 17, 2008 and at retail on November 18, 2008 in North America, In Australia on November 18, 2008 and on November 21, 2008 in Europe and Japan. Set during the aftermath of an apocalyptic pandemic, the game pits its four protagonists�dubbed the "Survivors"�against hordes of the infected. There are four game modes: a single-player mode in which allied characters are controlled by AI; a four-player, co-op campaign mode; an eight-player online versus mode; and a four-player survival mode. In all modes, left 4 dead cd key store,left 4 dead serial number,an artificial intelligence (AI), dubbed the "Director", controls level pacing and item spawns, in an attempt to create a dynamic experience and increase replay value. Left 4 Dead was well received by the industry media upon its release, with praise given for its replay value, focus on cooperative play, and movie-like experience. Several criticisms were aimed at limited level selection and the lack of a narrative. The game has won several publication awards, as well as distinctions from the Academy of Interactive Arts & Sciences and British Academy of Film and Television Arts. As was done with Team Fortress 2, Valve plans on supplementing the game with free downloadable content. The first of these, called the "Survival Pack", was released on April 21, 2009. The second piece of DLC was charged for via Xbox Live and came in the form of a new Campaign entitled "Crash Course," released for both the PC and Xbox 360 on September 29, 2009. The popularity of the game led to the development of a sequel,left 4 dead serial code, Left 4 Dead 2, which was released November 17, 2009. Left 4 Dead will be brought to Mac OS X along with other Valve games in mid-2010, allowing for cross-platform support between PC and Mac versions. The game has 5 campaigns but all of them have a fixed storyline. All of them (except for Crash Course) have 5 levels. No Mercy - After a narrow escape from the infected, the survivors had traveled through the apartments, the subway and the horrible underground. They reached the hospital and as they reached the rooftop, they called a rescue and they escaped in it. Crash Course - Unfortunately for the survivors, the helicopter pilot turns into an infected as the helicopter crashes into the industrial district. They find that the truck is the only vehicle that helps them escape, eft 4 dead store,buy left 4 dead,but it was a Truck-Depot and they activates the generator and escapes with the tuck. Death Toll - Upon finding that the highway was being blocked the abandoned cars, they forced to travel on with their feet, heading through the drainpipe. As they reached the church, the safe house door was locked by an madman who later turns into an infected. They walk through the streets and finally the boathouse and called a rescue and they escaped with it. Dead Air - The survivors woke up next morning, but was disappointed to find that the boat gas is running low, so the boat drivers have to park the boat outside the greenhouse. The survivors got off the boat and got into the greenhouse, leaving the boat vulnerable. The survivors had traveled through the hotel building, and the construction site. As they reached Metro Int'l Airport, they were shocked to see that airport was bombed by the army. They got through the terminals and the dismantled runway and called a rescue. They escaped with the plane. Blood Harvest - Unfortunately for the survivors, the plane pilot, who had rescued them in Dead Air, had turned into an infected and the plane crashes. Upon leaving the plane, they survivors find themselves in a thick forest and they traveled through a abandoned warehouse, a bridge and a train station, as well as a farmhouse. They called a rescue and they got away in the military truck.