Chess puzzle (Checkmate)
Moves: 1. d4 Nf6 2. Bg5 e6 3. e4 Be7 4. e5 Nd5 5. Bxe7 Nxe7 6. c4 c5 7. dxc5 Qa5+ 8.
Nc3 Qxc5 9. f4 Qe3+ 10. Qe2 Qxf4 11. Nh3 Qd4 12. Nb5 Qc5 13. Nd6+ Kf8 14. Ng5
Nf5 15. Ndxf7 Nc6 16. Nxh8 Ncd4 17. Qf2 Qb4+ 18. Kd1 Qa4+ 19. Kc1 Nb3+ 20. Kb1
Nxa1 21. Kxa1 *
Position (FEN): r1b2k1N/pp1p2pp/4p3/4PnN1/q1P5/8/PP3QPP/K4B1R b - - 0 21
Black to move.
Themes:  Middlegame Back Rank Mate, Mate in 1 
Puzzle rating: 661
Best move: Qd1#