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MatPlus.Net Forum Misc Construction task
 
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(21) Posted by Kevin Begley [Sunday, Sep 27, 2009 19:08]; edited by Kevin Begley [09-09-27]

Ahh, the subtle beauty of fairy elements in construction tasks.
Infinite coverage, from a single unit.

How about we add an excelsior.
Place this "non-capturing immune and transparent pawn" on a2, and directmate in infinity.
 
   
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(22) Posted by Joost de Heer [Sunday, Sep 27, 2009 19:21]; edited by Joost de Heer [09-09-27]

Obviously, the board should be 8x8 (the orthodox case can be improved on a 1000x1000 board too). The white king should be present too, and there should be a legal last move. 'Promotion to UU allowed' is a non-acceptable fairy condition, IMO. Any piece promoted to should be present in the diagram. So this requires at least 3 pieces: The white king, the white pawn, and the black UU.

(= 2+1 )

Madrasi, =UU

(last black move was KxUU, Madrasi is only used for legalising the position)
1. ab8=UU# on 60 squares.
 
 
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(23) Posted by Andrew Buchanan [Wednesday, Nov 11, 2020 04:16]

Great work! A few tiny comments on earlier Ubiubi problems...

bP=ubiubi
(= 2+2 )
Kriegspiel #1
This is dualed when sK is on f7, as g8=U# also mates.

(= 2+1 )
Kriegspiel #1
A position missing wK is *exactly* (to the nearest Planck length) as illegal as a position with White to play already checking bK, so sK may indeed be on g8, and hence no solution.

(= 1+1 )
Kriegspiel #1 wP Royal
Black might have just played e.g. Kh6xPh7, capturing another Royal wP, by dynasty rule. Only now is surviving wP Royal and hence in check.

(= 2+1 )
Kriegspiel #1 Madrasi.
This works, but Black might have also just played Kb6xc7 or Kc7xb6 without a White ubiubi involved. Setting up open Madrasi positions with multiple ubiubis presumably takes some chaperoning.
 
   
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(24) Posted by Joost de Heer [Wednesday, Nov 11, 2020 07:01]

 QUOTE 
This is dualed when sK is on f7, as g8=U# also mates.

Yes and no. g8=UU is not a dual when the sK is on f7, since you have to find a move that will work wherever the black king is.
But 1. g8-UU is a cook for another reason: It is a legal Kriegspiel move wherever the black king is, and if claimed illegal due to selfcheck, the next move white tries is 1. gh8=UU.

 QUOTE 
A position missing wK is *exactly* (to the nearest Planck length) as illegal as a position with White to play already checking bK, so sK may indeed be on g8, and hence no solution.

In orthodox chess, I agree. But in fairy chess not. Retro play is not applicable for fairy compositions (unless explicitly required), so a diagram without white king is a legal position. A king in check with the side that gives check on the move is still illegal however.
 
 
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