77. the cannon fires over a black piece, by the cannon

Helpmates in xiangqi

4 moves

Black moves first and both sides cooperate: Black, Red, Black, Red, and Red's second move mates. Black has 40 legal first moves and exactly one of them works. 16 pieces, Black 45 to Red 6.5 in material, mate by the cannon. Themes: the cannon fires over a black piece, Black blocks…