White is dead, ie; on ......Queen takes Bishop, White has Rook to h8 mate.
Only other choice for White is K to f1. Then straightforward is Bishop takes Rook, Queen takes Queen ( what else could Black do ?), Pawn takes Queen, King takes Bishop. My choice then would be Rook to h2.
If White then guards his pawns with K to d1, then Rook to d2 followed by Rook to d 8 followed by pushing on the "f" pawn forcing a Queen is easy.
After this move
...X1. Bxf1.
White has 2 Choices: either take the bishop with the queen or play ...Kf1.
In both cases Black can play Rh1+ !! on the next move!
First line goes like this:
...X1. Bxf1
X2. Qxf2 Rh1#
the other one:
...X1. Bxf1
X2. Kf1 Rh1+ //the only chance to defend against the check is to
//capture the rook with the queen!
X3. Qxh1 Qxh1+
X4. Kxf2 -> black has a queen against a white rook.
There is a 3rd variation where black is a rook up in material:
...X1. Bxf1
X2. Kf1 Bxe1+
X3. Qxf3 gxf3
X4. Kxe1 Rh2 -> white can resign aswell
On occassion there are very complex problems rated 800-900, such as 0035171.
The problem is rated for 3 moves, but it does not lead to any visible advantage (according to the board analysis, an advantage emerges for black only after 10+ moves). It does not lead to a mate, a mate threat, material gains or any other advantage during the problem. Are these problems intentionally created like this?