White to play and mate in four.
Mate in four.
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Just too difficult....
easy
I think I may know the moves...
y2721 wrote:
I think I may know the moves...
No engines 
It certainly wasn't easy, but I managed to solve it. The key to finding the first move is to notice how all of the obvious tries fail. 1.Nc4? fails to 1...c2, while 1.Ne4 fails to 1...Kd3. Also, 1.Qb5?! (cutting off d3) is a move too slow after 1...c2 2.Ne4 c1=Q 3.Qd7+ Ke5 4.Qd6+ Kf5 5.Qf6#. It was this last variation in particular that led me to the correct line:
1.Qd7! Kd3 2.Qf5+ Kd2 (2...Kd4 3.Nb5#) 3.Nc4+ Kc1/d1/e1 4.Qxb1#
1...Kc5 2.Nc8! Kb4 (else 3.Qd6+ Kb5 4.Qb6#) 3.Qa4+ Kc5 4.Qc4#
1...Ke5 2.Ne8! Kf4 (else 3.Qd6+ Kf5 4.Qf6#) 3.Qg4+ Ke5 4.Qe4#
1...c2 (or any other move) 2.Ne4+ Ke5 3.Qd6+ Kf5 4.Qf6#
The middle two variations are of course the most thematic, and they are mirror images of each other. A well composed problem. :)