Chess

Here's a first-prize-winning problem composed by C Jonsson in 1973. It's a series help-mate, which means that Black must make all the moves to reach a position in which White can mate in one. None of Black's moves, except possibly the last, may give check. And he has 35 moves to do it.

The mating move must clearly be axb5, which means that the black king will have to be on c6, surrounded by his own men. The piece on b7 will have to be a bishop, which means that the d-pawn has to promote. In fact, all the pawns must promote, which will take up 20 moves. The king needs three more to get to c6, which cuts things fine for getting the promoted men to their destinations. Here's the answer:

1.c3, 2.c2, 3.c1=R, 4.Rc7, 5.Kc4 6.Rb3! 7.e3, 8.e2, 9.e1=N! (a bishop is impossible as it gives check) 10.Nd3, 11.Nc5, 12.d4 (the knight had to get to c5 to allow this without a check from the rook on e5) 13.d3, 14.d2, 15.d1=B, 16.Bf3, 17.Bb7, 18.Kd5, 19.Kc6, 20.Rd5, 21.e5, 22.e4, 23.e3, 24.e2, 25.e1=R, 26.Re6, 27.Red6, 28.e5, 29,e4, 30.e3, 31.e2, 32.e1=R, 33.Ree7, 34.Red7, 35.Rb5+ when axb5 is mate. Bravo!