How to play
Three pieces a side — king, bishop, rook — moving exactly as in chess.
Nothing is ever captured; pieces only block one another.
A king may never move straight back to the square it just left. That
restriction lasts until the king moves again, and it applies even when
escaping check. The board marks the forbidden square.
You lose the moment your king has nowhere legal to go at the start of
your turn — whether or not you are in check, and whether or not your
other pieces can still move.