Chess puzzle (Advantage)
Opening: Scotch_Game, Scotch_Game_Other_variations
Moves: 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Nxd4 5. Qxd4 Qf6 6. Be3 Qxd4 7. Bxd4 d6
8. Nc3 Be6 9. Bd3 Ne7 10. O-O-O Nc6 11. Be3 g6 12. Nb5 O-O-O 13. Nxa7+ *
Position (FEN): 2kr1b1r/Npp2p1p/2npb1p1/8/4P3/3BB3/PPP2PPP/2KR3R b - - 0 13
Black to move.
Themes:  Middlegame  
Puzzle rating: 814
Best move: Nxa7