Selfmate in 4

It’s clear that the rook on f4 is the executioner-in-waiting. The task is cut out for White: to clear the path between bRf4 and wKf8 by briskly removing each intervening unit, like sweeping debris from the mouth of a primed cannon. 1.Qa2!, an ambush key, quietly sets the plan in motion. Lining up three sacrifices in a row, it threatens 2.Re7+ Nxe7 (A) 3.Be6+ fxe6 (B) 4.Ne5+ fxe5# (C).

A thematic reply is 1...Qh5, the black queen’s gaze shifting like a shadow to x-ray e5 instead of e7, prompting the sacrifices to realign in a new rhythm: 2.Be6+ fxe6 (B) 3.Ne5+ fxe5 (C) 4.Re7+ Nxe7# (A). Likewise, 1...Rg5 offers another thematic defence. The rook now casts its eye on e5 instead of e6, nudging the sequence to reorder yet again: 2.Ne5+ fxe5 (C) 3.Re7+ Nxe7 (A) 4.Be6+ fxe6# (B).

There’s a mathematical elegance in the synchrony of the second, third, and fourth moves—revealed the moment we assign them letters. The ABC of the threat rotates to BCA with 1...Qh5, and to CAB with 1...Rg5, forming a perfect cycle, like the hands of a finely tuned clock.

A side variation deepens the charm: after 1...Nd4 or 1...Ng7, White continues with 2.Be6+ Nxe6+ 3.Qxe6+ fxe6 4.Ne5+ fxe5#, the sacrifices still cascading but off the main axis, a soft-spoken detour, humming with its own quiet logic.

Finally, the astute solver will notice the tries 1.Qb3? and 1.Qc4?, which carry the same threat as the key but are refuted by 1...Rf3! and 1...e3!, respectively, as Black exposes the f-rook to White's queen, slipping a spanner into the works.

A true masterpiece!