One board, everybody plays White. Drag a piece or tap it and tap where it goes. Black is one of 28 opponents - the eighteen deliberately terrible chess engines from Tom 7's Elo World, eight more written in the same spirit, and three that are really Stockfish playing at material odds. New boards prefer whoever has played least. You cannot play two moves in a row - somebody else has to move in between. One turn in ten the machine gets a bonus move and plays twice. Checkmate it and every player is paid 1 coin for each move they contributed; three votes clears the board and deals a new opponent.

Chess pieces by Cburnett, via Wikimedia Commons, used under CC BY-SA 3.0 / GFDL / GPL and recoloured.