The cavalier is a knight, but may also jump to the opposite corner of a rectangle two squares by four (i.e., it moves like a Gnu.) The general is rook plus knight; the commander is queen plus knight. Castling is possible if the king and rook are both on their original squares (though one or both may have moved) and the squares between them are unoccupied and no square traversed by the king is attacked. The king moves as many squares toward the rook as desired (two minimum), then the rook leaps over the king and moves as many squares beyond him as desired (or as are available). Other rules are as in standard chess.