Originally posted by greenpawn34I think he said mate on the move, so one move to mate but only one legal move.
This fits the criteria.
By Ropke. White to play and mate in 6 moves.
[fen]K1k5/P1Pp4/1p1P4/8/p7/P2P4/8/8 b - - 0 1[/fen]
Don't be put off by the six moves.
Teach anyone how to play chess and they will solve it right away.
All it requires is that both sides play their only legal moves.
The problem actually solves itself.
[FEN "K1k ...[text shortened]... 1p1P4/8/p7/P2P4/8/8 w - - 0 1"]
1. d4 b5 2. d5 b4 3. axb4 a3 4. b5 a2 5. b6 a1=Q 6. b7[/pgn]