Chess puzzle (Checkmate)
Moves: 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6 5. Nc3 Qd6 6. d3 Bg4 7. Be3 f6 8.
Qe2 O-O-O 9. O-O-O c5 10. Rd2 Ne7 11. Rhd1 Nc6 12. Nd5 Nd4 13. Bxd4 cxd4 14. a3
Be6 15. Nb4 c5 16. Na2 Bxa2 17. Nh4 c4 18. Qg4+ Kb8 19. dxc4 Qxa3 20. bxa3 *
Position (FEN): 1k1r1b1r/1p4pp/p4p2/4p3/2PpP1QN/P7/b1PR1PPP/2KR4 b - - 0 20
Black to move.
Themes: Queenside Attack Middlegame Double Bishop Mate, Mate in 1 
Puzzle rating: 852
Best move: Bxa3#