Here's a puzzle which is impossible to do at GameKnot. The position of the two knights alone guarantees mate in 2 (e.g. Nh6+ Kh8, Ng6#). The object is to move your c2 pawn up the gauntlet of black pawns and not lose nor capture a single piece, then checkmate the king with your pawn in the last move.
Don't cheat!
1. Qd1 Kh8
2. Qb1 Kg8
3. Qa2 Kh8
4. Ng3 Kg8
5. Ng2 Kh8
6. Ne2 Kg8
7. Ne1 Kh8
8. Nc1 Kg8
9. Rf8+ Kg7
10. R6f7+ Kh6
11. Rh8+ Kg5
12. Bh4+ Kg4
13. Bf5+ Kf4
14. Ncd3+ Ke3
15. Ra7 Kd2
16. Kf2 Kc3
17. Kf3 Kd2
18. Qb2 Kd1
19. Bg4 Kd2
20. Ra6 Kd1
21. Kg2+ Kd2
22. c4+ Ke3
23. Qc1+ Ke4
24. Bf3+ Kf5
25. Qg5+ Ke6
26. Bg4+ Kf7
27. Bh5+ Ke6
28. Rh6+ Kd7
29. Qd8+ Kc6
30. c5 Kb7
31. Qa8+ Kc7
32. Bd8+ Kd7
33. c6#