Chess puzzle (Advantage)
Opening: Kings_Pawn_Game, Kings_Pawn_Game_Busch-Gass_Gambit
Moves: 1. e4 e5 2. Nf3 Bc5 3. Nxe5 Nf6 4. Nc3 Nc6 5. Nxc6 dxc6 6. Bc4 Qd4 7. Qe2 O-O
8. d3 Bg4 9. f3 Be6 10. Bxe6 fxe6 11. Bd2 b5 12. a3 Rab8 13. e5 Nd5 14. Rb1 b4
15. Na4 *
Position (FEN): 1r3rk1/p1p3pp/2p1p3/2bnP3/Np1q4/P2P1P2/1PPBQ1PP/1R2K2R b K - 1 15
Black to move.
Themes:  Middlegame  
Puzzle rating: 1600
Best move: bxa3