White to play and mate in 13. What do you think should be the first move?

Black has played 1...Bf2+. Of course, 1...Be5 (guarding g7) is of no help due to 2.Nf4+ Bxf4 3.g4#. How should White continue from here?

1...Bf2+ 2.Nc5! Bg3 - the bishop goes back, stopping g4#. How should White continue?

1...Bf2+ 2.Nc5! Bg3 3.Nd7! Bf2+ - Black persists with the checks. How should White continue?

4.Nb6! Bg3. How should White continue from here? We've maneuvered the knight to b6 but what purpose does it serve?

4.Nb6! Bg3 5.c4!! Bxc4 - By forcing Black's light-squared bishop to c4, White has achieved something important here. What is it? White to play!

But now, again, 6...Bf2+ - How should White continue?

6...Bf2+ 7.Nc5! Bg3 - How should White continue?

Again, 8.Bf2+ - What should White play?

8.Bf2+ Nd4! 9.Bg3 - the knight has finished its journey back. Now, what should White play?

10.Kb8 b1=Q - Black queens his pawn, but can he still stop the mate? White to play!

Finally, what happens after 11...Qb2?

Finally, what after 12...Bxf4?