Here is a chess problem I've made that has an illegal position. The board is from White’s view and White’s d1 pawn moves normally. Have fun!
White moves and mates in 19 moves
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Sign up to join this communitySame basic idea as Barsloai, but refined a bit to actually achieve mate in 19. All of black's lines should be accounted for.
[FEN "5brb/4p1p1/3pPpPp/3p3P/7p/5PpP/PP4Pp/3P1K1k w - - 0 1"]
1. b4 f5 {Black can move pawns in a different order, but it won't matter.}
2. b5 f4
3. b6 d4
4. b7 d5
5. b8=Q d3
6. Qb2 d4
7. a4 d2 {d2 cannot be the last pawn move, so d2 must have been made by this point regardless of move order.}
8. Qxd2 d3 {Last pawn move; variations have collapsed.}
9. Ke1 Kg1
10. Qxd3 h1=Q (10... Kh1 11. Qf1#)
11. Qf1+ Kh2
12. Qxh1+ Kxh1
13. Kf1 Kh2
14. a5 Kh1
15. a6 Kh2
16. a7 Kh1
17. a8=Q Kh2
18. Qa7 Kh1
19. Qg1#
I thin this. should work. Excuse me for not knowing exactly how to describe chess move in English as normally I do it in my native tongue-hopefully you'll understand
1. b4, d4 2. b5, d3 3. b6, d2 4. b7, d5 5. b8=Q, d4 6. Qb2, d3 7. Q:d2, f5 8. Ke1, f4 9. Qb1, d2 10. Q:d2, Kg1 11. Qe2, h1>Q 12. Qf1+, Kh2 13. Q:h1, K:h1 14. Kf1, Kh2 15. a4, Kh1 16. a5, Kh2 17. a6, Kh1 18. a7, Kh2 19. a8>Q, Kh1 20. Qa7, kh2 21. Qg1 #