 Another significant element removed was a long introduction between campaigns; because the game is designed for replayability, it was difficult to hold the player's attention for repeated viewings of cut scenes, so they were dropped in favor of a sparse narrative.Also, the game started out with one big city design with many routes for the survivors, but playtesters were confused when they began to play, and later they always chose the same route; ultimately Turtle Rock Studios cut the city maps into the first "No Mercy" and "Dead Air" campaigns.Certain Affinity assisted Turtle Rock Studios with the Xbox 360 version of the game.