Can someone explain the solution of this puzzle to me. I think I'm missing a broad idea that perhaps makes solving this easier than brute forcing the calculation of multiple lines. Correct move is Qa7+, what themes should I be aware of to be able to find this.
It is worth noting, database has four moves winning for black in this position: Qa7+ (the solution), Qf1, Qh1+, and Qa8, but after white replies with Kg7 against all lines except the solution, the only winning move becomes going back to Qa1 with the idea to play Qa7+ once again. Letting Stockfish 12 sit on this position until depth 30ish, confirms that Qa7+ is the only winning move here.
Any help analyzing this would be appreciated.
