Plants vs Zombies was released by PopCap in 2009 as a tower defense game where plants defend a lawn against waves of zombies. Its level structure builds tension around announced huge waves, making the sound that marks a wave as defeated a familiar reward cue for players who spent hours protecting their house. As gameplay clips and edits moved to YouTube and social platforms, the sting was lifted as a standalone effect. It remains popular because its meaning is understood without context, a clear signal that a challenge has ended.