Chess puzzle (Advantage)
Opening: Queens_Pawn_Game, Queens_Pawn_Game_Colle_System
Moves: 1. d4 d5 2. e3 Nf6 3. Nf3 Nc6 4. Nc3 Bg4 5. Qd3 Bxf3 6. gxf3 Nb4 *
Position (FEN): r2qkb1r/ppp1pppp/5n2/3p4/1n1P4/2NQPP2/PPP2P1P/R1B1KB1R w KQkq - 1 7
White to move.
Themes:  Opening  
Puzzle rating: 800
Best move: Qb5+