This week we shift genres to the selfmate. White moves first, and his task is to force
a reluctant Black to mate him – unlike in helpmates, there is no cooperation
involved here, and Black has to be forced into a position where his only legal move(s)
mate White.
For a start, we have set play. If it were Black to play, his only two legal moves would
be 1...Sxf4 and 1...Sxg3. On closer inspection, we see that the former can be answered by
2. Be2+, when Black's only legal move is 2...Sxe2 mate, whilst the latter runs into
2.Bxb3, when Black's only legal moves are 1...Sxb3 mate and 2...Rxb3 mate.
However, it is White to play, and he has no waiting move that preserves these mates.
Instead, the key is 1.Qd4! which leaves Black with the same choice of moves, Now,
however, it turns out that 1...Sxf4 is met by 2.Bxb3 and 1...Sxg3 by 2.Be2+, forcing mate
in each case, a neat reciprocal change.