The Hopper Issue 4 is here

I feel that better would be:

wKg3, Nc8 = 2. bKh1, bTd6, bSf2 = 3.

H#3, 2 solutions. 1. Sg4 Ne7 2. Sh2 Kf2#   1. Sh3 Nxd6 2. Sg1 Nf2#

@Laco but this lacks the thematic tempo moves by bS in each twin

Alas anticipated by Lkhundevin Togookhuu, 1987-88 Commended 8/1K6/1p6/1P6/2P5/3p1p2/3Ppp2/r2Rsk1B h#4

It can be done without a twin:
Kg3, Nd1, Pd3 - Kh1, Sf2 (3+2)
I. 1.Sg4 Nf5 2.Sh2 Kf2#
II. 1.Sh3 d4 2.Sg1 Nf2#

Or
Kg3, Nb1 - Kh1, Sf2 (2+2)
h#2, 2 solutions - but without a pair of checkmates on f2.

In PDB, Michael Schreckenbach (SHRECKE) offered in response R4r1k/pPP3R1/rp3PKn/p5PQ/P7/8/8/8 s#2 (-: with 6 dummy promotions!

Surprising to me that parity can affect such a long game with numerous wanderings & captures. Declaration of castling rights is normal in this space, which began in a (still open) question of how many vampires exist in chess.

Since Popeye does not support Quintessence Lion, Quintessence piece was used instead to be showcased!

Version with wPf3 on f4 has more clarity & unity. Just 3 tries instead of 54.

Thank you for solving this - however, this problem has exactly one intended solution (and the reason why the other apparent solution is not the intended solution is the theme of this problem.)

Nicely matched solutions!!

(White Pawn on b6 isn't needed.)

Misses (two solutions) in the stipulation.

Multiple change to 1...Sxf7 is nice.

Two variations with White AB-BA plus two remote blockings variations.Nice!

Wow that's a great addition AOP!

Hint move for solvers: In two solutions you make an underpromotion move from c1 and than block the flight b1 of bK.
A.Okan.P.
(If you like the 'algorithm' of the problem you can solve an extra twin: d) bPb2 to c3 (Only Kings moves)

Tricky proof game to solve by hand with many apparent degrees of freedom.

Nice tight problem with harmony between the solutions. Some letter problems draw the board, but here all the pieces play a part and can't be replaced by weaker ones. Thanks so much!

Thanks for the version, aop.
There's a kind of non-debate in MatPlus at the moment about the merits of twins versus two solutions. Basically questions of harmony, balance etc are more important drivers. To my mind, two solutions edges out twins to the same extent that unique promotion to queen edges out tolerated dual promotion. Other kinds of twinning (zero position, multiple changes to diagram) are intolerable to the same extent as dual promotion as a non-mating move.
I don't want to say more now at risk of spoiling.
 

Thank you Laska!

In any case if I understand well what you say, I don't really know what "is" a theme.

A kind of paradox maybe that themes are very important, clarity and accuracy are important too, but definitions are easily too narrow, too tight, so a kind of flexibilty in the way we understand things is often welcome.

Author's comment: It is clearly possible to have a wenigsteiner with KRXvK, which would extend by 100 moves, but so many of these already exist, albeit without the retro angle. However the current position attracted me because of the Function Exchange between white officers and also between black officers, so I decided to linger here.

Remarkable & fluent: bravo, Jacques! :) Also (if I can say without spoiling) it contributes to the debate of what *is* a theme. Maybe at the core of what is often described as a theme is an *effect*. The particular mechanism for delivery maybe different. For example, the Berlin theme is defined in the context of the logical school. So a #2 in which try defences are checkmates has to be described as "quasi-Berlin" which is horrible. There is a Berlin *effect* and that can be manifest in different ways. I think the same thing is happening in this problem. What do you think? 

Very entertaining. Is this the shortest such mate possible?