Countdown first aired on Channel 4 in 1982 as a letters and numbers game show, and its 30 second clock round became the format's signature moment. Contestants work against the ticking music while the large studio clock counts down, a setup copied by international versions of the show. Clips of the theme spread online as a ready made timer for quizzes and challenges, and the sound is now used far beyond the programme whenever a short, fair and very recognisable deadline is needed.