Chess puzzle (Advantage)
Moves: 1. Nf3 d5 2. c4 d4 3. e3 d3 4. Ne5 Bf5 5. Qb3 Na6 6. Bxd3 Nc5 7. Qb5+ c6 8.
Qxc5 Bxd3 9. Nxd3 Qxd3 10. Qb4 Qd7 11. d4 a5 12. Qb3 a4 13. Qc2 Nf6 14. Nc3 b5
15. cxb5 cxb5 16. O-O e6 17. Bd2 Bd6 18. h3 O-O 19. b3 Rac8 20. bxa4 *
Position (FEN): 2r2rk1/3q1ppp/3bpn2/1p6/P2P4/2N1P2P/P1QB1PP1/R4RK1 b - - 0 20
Black to move.
Themes:  Middlegame  
Puzzle rating: 1536
Best move: b4