Lichess puzzle 87510 has this position.
[FEN "r1b1k3/pp4R1/2q3RQ/4p3/5P2/bP2P3/2P1K2P/8 b - - 0 1"]
The solution is 1...Bg4+,.after which White has 6 legal moves:
- 1...Bg4+ 2. Rxg4 Qxh6, which is the computer solution, possibly followed by 3. Rg8+ Bf8,
- Kd3, which is mate in 7,
- Kd2, which is mate in 8,
- Ke1, which is mate in 5,
- Kf1, which is mate in 4, and
- Kf2, which is mate in 4.
I feel like a human player in a tournament would not calculate the whole decision tree, and probably just intuit that 1...Bg4+ is going to win since black can continue with a range of powerful moves Qf3, Qc2, Rd8, and Bb4 and at least one of them is with check, depending on White's response.
Question: How much calculation would a strong player (say an FM+) perform before playing 1...Bg4+?
It's a dangerous move Black begins with an exposed king, with mate threats and a possible rook skewer, and queen attacked, and Black responds by creating an undefended bishop. If the checks ended, Back would probably lose.
PS black has already castled