inst swarming zombie hordes and terrifying mutant monsters. 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. New technology dubbed "the AI Director" is used to generate a unique gameplay experience every time you play. The Director tailors the frequency and ferocity of the zombie attacks to your performance, putting you in the middle of a fast-paced, but not overwhelming, Hollywood horror movie. Addictive single player, co-op, and multiplayer action gameplay from the makers of Counter-Strike and Half-Life Versus Mode lets you compete four-on-four with friends, playing as a human trying to get rescued, or as a zombie boss monster that will stop at nothing to destroy them.