The other choice of moves to be made is Nxd1 or Nxf1. I tried the Nxf1 route, but it fails because as pointed out before, black needs to play the queen to h-file as soon as possible, and it appears too fast for white to get the king to h2, his queen toh1 and then both back in reversed order. So, Nxd1 it is. From then on, white's moves are limited to the king going between e1 and d1. Luckily enough, with the right parity of moves.
Now we know all the moves, remains the order in which to play the black ones. Not too hard to find out that the rook from h8 needs to get out before b5 is played. The rest is pretty simple:
1.Nf3 a5 2.Nd4 a4 3.Nb3 axb3 4.a4 (no need for the spare move, and no time either) f5 5.Ra2 bxa2 6.Rg1 axb1=N 7.Rh1 Nc3 8.Rg1 Nxd1 9.Rh1 Nc3 (not via Ne3 because the f-pawn is in the way) 10.Rg1 Ne4 11.Rh1 Ng3 12.hxg3 f4 13.Rh6 f3 14.Rd6 cxd6 15.Kd1 Qa5 16.Ke1 Qh5 17.Kd1 Qh1 18.Ke1 h5 19.Kd1 h4 20.Ke1 Rh5 21.Kd1 Rb5 22.Ke1 g5 23.Kd1 Bg7 24.Ke1 Bc3 25.Kd1 Ba5 26.Ke1 Rb4 27.Kd1 b5 28.Ke1 Bb7 29.Kd1 Bd5 30.Ke1 Nc6 31.Kd1 0-0-0 32.Ke1 Kb7 33.Kd1 Rc8 34.Ke1 Nd8 35.Kd1 Rc3 36.Ke1 Ra3 37.Kd1 Ra1 38.Ke1 Ba2 39.Kd1 d5 40.Ke1 Qxf1+.
Originally posted by Mephisto2The real difficulty in the problem is figuring out the first ~15 moves. The extra length doesn't really make it more difficult than most PG~15's, for after ...Qh1, Black's remaining moves are a rather obvious sequence.
The other choice of moves to be made is Nxd1 or Nxf1. I tried the Nxf1 route, but it fails because as pointed out before, black needs to play the queen to h-file as soon as possible, and it appears too fast for white to get the king to h2, his queen toh1 and then both back in reversed order. So, Nxd1 it is. From then on, white's moves are limited to the ki ...[text shortened]... 1 Kb7 33.Kd1 Rc8 34.Ke1 Nd8 35.Kd1 Rc3 36.Ke1 Ra3 37.Kd1 Ra1 38.Ke1 Ba2 39.Kd1 d5 40.Ke1 Qxf1+.