Chess puzzle (Advantage)
Opening: Rat_Defense, Rat_Defense_Harmonist
Moves: 1. e4 d6 2. f4 Nf6 3. Nc3 Bg4 4. Nf3 e5 5. f5 Be7 6. Be2 O-O 7. h3 Bxf3 8. Bxf3
Nbd7 9. d4 c6 10. Be3 exd4 11. Bxd4 Re8 12. Qd2 Ne5 13. O-O-O Nxf3 14. gxf3 a5
15. a3 b5 16. h4 b4 17. Nb1 bxa3 18. Nxa3 d5 19. e5 Bxa3 *
Position (FEN): r2qr1k1/5ppp/2p2n2/p2pPP2/3B3P/b4P2/1PPQ4/2KR3R w - - 0 20
White to move.
Themes:  Middlegame  
Puzzle rating: 1197
Best move: exf6