Ultimate Chess

Chess with everything the rules require and nothing they do not: castling, promotion, check and checkmate, and a move history you can read back. Pieces are moved by clicking the piece and then the square, with legal moves marked in green and captures in red, so a beginner can play a full game without knowing the notation. The computer offers three strengths, but the reason this one is in the archive is the player-against-player mode, which turns a browser tab into a board on a table.