I'm afraid it is not about the 21st and 22nd moves of the game, but about moves 1 up to 20 😕
Black's options to reach this position in 20 moves are limited, because the LEAST number of moves is 20:
- 7 pawn moves (at least 6 of them are captures)
- 3 bishop moves (Bf8-e7 and Bc8-b7 and Bb7-(xR)a1
- 3 knight moves Ng8 - h6 (more likely than via e7) - f5 - h4
- the knight on b8 has not moved and was captured on b8
- 2 king moves including 0-0
With the d-file temporarily open:
- 1 queen move
- 2 rook moves (after the castling) Rf8 - d8 (more lilely than via f4) - d4
- 2 more rook moves Ra8 - (x) a2 - c2
Building on the above, the following seems to do the job:
1.c3 Nh6 2.Qa4 Nf5 3.Qxa7 Nh4 4.Qxb8 Rxa2 5.b3 Rc2 6.Ra6 bxa6 7.Qb6 Bb7 8.g4 Bxh1 9.Bg2 cxb6 10.Bc6 dxc6 11.Ba3 Qd3 12.Bd6 exd6 13.e4 Be7 14.e5 0–0 15.e6 fxe6 16.g5 Rf4 17.g6 Rd4 18.f4 hxg6 19.f5 Kh7 20.f6 gxf6
Originally posted by Mephisto2Oh, I see...haha... yes, even though I've seen many puzzles of this sort here, it didn't even cross my mind that's what it was, sorry...
Building on the above, the following seems to do the job:
1.c3 Nh6 2.Qa4 Nf5 3.Qxa7 Nh4 4.Qxb8 Rxa2 5.b3 Rc2 6.Ra6 bxa6 7.Qb6 Bb7 8.g4 Bxh1 9.Bg2 cxb6 10.Bc6 dxc6 11.Ba3 Qd3 12.Bd6 exd6 13.e4 Be7 14.e5 0–0 15.e6 fxe6 16.g5 Rf4 17.g6 Rd4 18.f4 hxg6 19.f5 Kh7 20.f6 gxf6