Lichess is a free, open source chess server launched in 2010, and its arena tournaments introduced berserk mode as a voluntary handicap. A player who clicks the berserk button starts the game with half their original time and no increment, but earns an extra tournament point for a win. The short berserk sound became the audible cue for that decision, shared by streamers and editors outside the site as shorthand for choosing speed and risk over safety. It remains closely tied to fast online chess culture and late arena comebacks.