Chess puzzle (Advantage)
Opening: Philidor_Defense, Philidor_Defense_Hanham_Variation
Moves: 1. e4 e5 2. Nf3 d6 3. d4 Nd7 4. Bb5 c6 5. Ba4 b5 6. Bb3 g6 7. c3 Bg7 8. O-O
Ngf6 9. Nbd2 O-O 10. Re1 a5 11. Nf1 a4 12. Bc2 Nh5 13. Ng3 Nxg3 14. fxg3 Nf6
15. Be3 Bg4 16. Qd2 Qa5 17. Bh6 Bxh6 18. Qxh6 a3 *
Position (FEN): r4rk1/5p1p/2pp1npQ/qp2p3/3PP1b1/p1P2NP1/PPB3PP/R3R1K1 w - - 0 19
White to move.
Themes:  Middlegame  
Puzzle rating: 1040
Best move: b4