Left 4 Dead is Valve's cooperative first-person shooter in which four survivors fight through hordes of infected, and its audio has become a familiar shorthand for zombie-game tension online. Numbered clips like this one are usually short excerpts uploaded to soundboards by players, rather than official soundtrack tracks, and they spread through gameplay videos, streams and memes. Because the game remains popular with modders and retro gaming fans, these brief cues still work as instant recognition signals for anyone who played the original.