Chess puzzle (Advantage)
Opening: Four_Knights_Game, Four_Knights_Game_Double_Spanish
Moves: 1. e4 e5 2. Nf3 Nf6 3. Nc3 Nc6 4. Bb5 Bb4 5. h3 h6 6. O-O O-O 7. a3 a6 *
Position (FEN): r1bq1rk1/1ppp1pp1/p1n2n1p/1B2p3/1b2P3/P1N2N1P/1PPP1PP1/R1BQ1RK1 w - - 0 8
White to move.
Themes:  Opening  
Puzzle rating: 1981
Best move: axb4