Chess puzzle (Checkmate)
Opening: Queens_Gambit_Declined, Queens_Gambit_Declined_Albin_Countergambit
Moves: 1. d4 d5 2. c4 e5 3. dxe5 d4 4. Nf3 Bb4+ 5. Bd2 Bxd2+ 6. Nbxd2 c5 7. Nb3 b6 8.
Qd3 Ne7 9. O-O-O Bf5 10. Qd2 Nbc6 11. e3 O-O 12. exd4 a5 13. d5 Nb4 14. a3 *
Position (FEN): r2q1rk1/4nppp/1p6/p1pPPb2/1nP5/PN3N2/1P1Q1PPP/2KR1B1R b - - 0 14
Black to move.
Themes:  Middlegame Mate in 1 
Puzzle rating: 887
Best move: Na2#