Chess puzzle (Advantage)
Moves: 1. e4 c5 2. Bc4 Nc6 3. Qh5 e6 4. c3 Nf6 5. Qf3 Ne5 6. Qe2 d5 7. Bb5+ Bd7 8.
Bxd7+ Qxd7 9. exd5 Qxd5 10. Nf3 Nd3+ 11. Kd1 Ne4 12. Rf1 Rd8 13. Ne1 Nxe1 14.
Rxe1 Nxd2 15. Bxd2 Qxg2 16. f3 Qg6 17. Qb5+ Rd7 18. Na3 Be7 19. Nc4 Qd3 20. Re2
O-O 21. a4 *
Position (FEN): 5rk1/pp1rbppp/4p3/1Qp5/P1N5/2Pq1P2/1P1BR2P/R2K4 b - - 0 21
Black to move.
Themes:  Middlegame  
Puzzle rating: 1856
Best move: a6