Chess puzzle (Advantage)
Opening: Philidor_Defense, Philidor_Defense_Exchange_Variation
Moves: 1. e4 e5 2. Nf3 d6 3. d4 exd4 4. Nxd4 Nf6 5. Bg5 Be7 6. Bd3 Bd7 7. a3 Nc6 8. c3
Nxd4 9. cxd4 h6 10. Bh4 O-O 11. O-O Bc6 12. d5 Bd7 13. f3 Qe8 14. Nc3 Nh7 15.
Bg3 Bf6 16. Rc1 a6 17. b4 Rc8 18. a4 Bxa4 *
Position (FEN): 2r1qrk1/1pp2ppn/p2p1b1p/3P4/bP2P3/2NB1PB1/6PP/2RQ1RK1 w - - 0 19
White to move.
Themes:  Middlegame  
Puzzle rating: 1259
Best move: Nxa4