The thematic content of this orthodox problem needs some explanations: it is a so-called “future proof game” – it means that, in parallel with the “helpmate of the future” setting, the content shows 2+2 unified thematic parts.

The white side demonstrates 2 Ceriani-Frolkin Queens (captured promotions), which are moreover captured in a crossed way - the motivation being a last checking half-move. The black side also demonstrates 2 Ceriani-Frolkin Queens, with a new specificity - each of them visits the initial Pawn square from which they are issued. The full content is symbolized by (CC & CF)(QQ) & (CF & PC)(q,q).

This theme is a kind of disjoint union of 2 previously existing renditions – one by Silvio Baier (15003 Die Schwalbe 2011 251), where the Pawn Circuit part is missing, and one by myself (P.95, N4 StrateGems 2015 70), where the Crossed Capture part is missing. Moreover those older renditions contain 6 captures, while the new one contains only 5, making the capture economy perfect, as N Ceriani-Frolkin pieces needs at least N+1 captures.

Finally note that solving programs (Euclide and Natch) asserts that the problem is sound until the last half-move, and that there is no solution at this step if the wQf6 is replaced by another piece type. An elementary retro argument then demonstrates that the full problem is correct. (Author)