

(1) Posted by Hauke Reddmann [Tuesday, Jun 4, 2024 10:59] 
Letters (Jurmala made me do it :) I daresay for any letter problem you need at least two black moves.
(Otherwise you maximally have the theme of "changed mate".)
Let's also assume that a set, a try and a real phase exists.
(Everything less would be a subset of the following.)
We thus have maximally six possible mating moves UVWXYZ to fill in,
plus  for not relevant and ! if A/B defends.
AB
SUV
TWX
RYZ
I have not computed how many letter themes this will make,
are you sure you already showed each and every of them?
Even only the interesting and the "nonsplit"? :) 

(2) Posted by Joost de Heer [Tuesday, Jun 4, 2024 12:44] 
QUOTE
I daresay for any letter problem you need at least two black moves.
Not really: Key, threat, one variation. 

(3) Posted by Hauke Reddmann [Tuesday, Jun 4, 2024 17:22] 
So what do you intend to show with only one black move?
Regardless how you permute !UVW, I don't see anything
else than a changed mate  what do I overlook?
(Unless, of course, you count the threat to the letters,
indeed then there already are 9 entries, 6w, 3b.) 

(4) Posted by seetharaman kalyan [Wednesday, Jun 5, 2024 19:15] 
Letter H# problems. Is it ok to have one solution? 

(5) Posted by Joost de Heer [Thursday, Jun 6, 2024 09:17] 
QUOTE
So what do you intend to show with only one black move?
Djurasevic cycle, Ceriani Cycle (and a Reeves cycle doesn't even require a black move, it's a cycle between key and threat). 

(6) Posted by Hauke Reddmann [Thursday, Jun 6, 2024 09:59] 
Guess I have to buy "Cyclone" somewhen after all :) 

(7) Posted by Juraj Lörinc [Thursday, Jun 6, 2024 21:34] 
It is not only about Cyclone.
Juraj Brabec has included in his recent book "Za vsetkym hladaj motiv" the analysis of various nonisomorphic types of Zxyzt types. There is just one change of type Z3226 (change of 2 mates in three phases), but there are e.g. 26 nonisomorphic changes of type Z3244, one of them with phase variations aAbBaCcBaDdC, other like aAbBaBbAcCdD (with clean radical change in one phase).
In spite of extended formalism (allowing classification of change themes) he underlines throughout the book the following: formal themes can be interesting, but the key interest lies in the underlying motivation. 

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