Portal 2 is Valve's 2011 sequel to Portal, set in the decaying Aperture Science facility ruled first by GLaDOS and later by Wheatley. Stalemate is part of the facility's core transfer procedure, triggered when the current and substitute cores disagree and a human must press the stalemate resolution button. The sequence became a favourite reference among players for its mix of danger and absurd procedure, and short clips of the announcement later spread in gaming edits as a shorthand for any locked, unresolved contest.