osu is a free rhythm game released in 2007, inspired by rhythm titles on the Nintendo DS, where players click, tap and slide to the beat of a song. Skins let players replace the default hit sounds, so different packs spread widely through gameplay videos, streams and custom skin downloads. This short tick became recognisable outside the game because it signals a successful hit so clearly. Creators still borrow it as instant audio shorthand for accuracy, timing and a satisfying click in edits.