pola

Set in the immediate aftermath of the zombie apocalypse, L4D's
survival co-op mode lets you blast a path through the infected
in four unique movies, guiding your survivors across the
rooftops of an abandoned metropolis, through rural ghost towns
and pitch-black forests in your quest to escape a devastated
Ground Zero crawling with infected enemies. Each "movie" is
comprised of five large maps, and can be played by one to four
human players, with an emphasis on team-based strategy and
objectives.