BeginnerRelated: Skewer
Skewer the King
White's bishop rakes the long diagonal straight through the king to the rook behind it.
Your Move
Black's king must move out of check. Find White's winning follow-up.
Solution: 1...Kg6 (forced) 2. Bxg7
The bishop on b2 already checks the king along the a1–h8 diagonal. Black's king must step off the diagonal (for example to g6), and White then plays Bxg7, winning the exchange — a rook for a bishop is a clean material gain even though the bishop can be recaptured afterward.