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.

Set in the days after a pandemic outbreak of a viral strain transforming people 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. Left 4 Dead is a series of cooperative first-person shooter survival horror video games published by Valve.