Duck chess

Chess with a duck. After you move a piece, you must move the duck to block any empty square.

Play as

Move a piece as normal, then click an empty square to move the duck there. It can’t stay where it was.
Nothing can land on or jump past the duck, except knights.
There’s no check or checkmate: capture the king to win.
If you have no legal moves, you win.

Pieces by Colin M.L. Burnett (GPLv2+).