Answers.Body: <p>This problem can be solved computationally using the powerful &quot;constraints&quot; feature of Francois Labelle's Jacobi engine: <a href="https://wismuth.com/jacobi/latest/solver.html" rel="nofollow noreferrer">https://wismuth.com/jacobi/latest/solver.html</a></p>
  <pre><code>&gt; option FirstToMove white 
  &gt; stipulation h#6
  &gt; condition Chess960 
  &gt; constraint Xa8(0..0) Xb8(0..0) Xc8(0..0) Xd8(0..0) Xe8(0..0) Xg8(0..0) Xh8(0..0) Pa7(0..0) Pb7(0..0) Pc7(0..0) Pd7(0..0) Pe7(0..0) Pf7(0..0) Pg7(0..0) Ph7(0..0)
  &gt; constraint Xf8!g8~
  </code></pre>
  <p>A few comments:</p>
  <ol>
  <li>option &quot;first to move white&quot; implies also that black will
  deliver the mate. I.e. it's the equivalent of &quot;halfduplex&quot; option in
  Popeye.</li>
  <li>Jacobi handles variable officer positions using &quot;X&quot; to
  specify unknown unit. Castling counts as a king move, so 15 black
  units are prevented from moving by specifying their minimum &amp;
  maximum number of moves as zero.</li>
  <li>We also say that the first move of the 16th unit is castling &quot;!&quot;, followed by any number of other moves, &quot;~&quot;.</li>
  <li>There are 360 solutions, all beginning &quot;1.c3/c4 O-O 2.Bxh7+ Kxh7&quot;.</li>
  <li>80% of the solutions follow the pattern given by Hauke, however there is an alternative approach where White also castles: (BBSSRKRQ) 1.c3 O-O 2.Bxh7+ Kxh7 3.O-O Kg6 4.h4 Kh5 5.Kh2 Kxh4 6.Rg1 Kg4#</li>
  <li>There are 9 different game arrays that work, 2 first moves, and 2 final blocking moves by wQ/R. There are then various other duals which lead to 8+2=10. 9x2x2x10=360.</li>
  <li>There are no solutions in 6.0 moves with queenside castling.</li>
  </ol>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-08-28T07:56:31.437Z
Answers.Text: Now that's solving in style :-) Too bad for the immanent 1.c3/c4 dual, or one could make a "real" problem out of it. Point 6 doesn't surprise me, running to the border then takes too long, and a discovered check on an "epauletted" king (my 1st attempt) takes around 8 moves.
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-08-28T06:13:50.763Z
Answers.LastActivityDate: 2024-08-28T08:54:44.463Z
Answers.LastEditDate: 2024-08-28T08:54:44.463Z
Answers.UserDisplayName: Laska
Answers.Body: <p>Pending a genius stroke from MatPlus, this might be the fastest way:</p>
  <pre><code>[FEN &quot;bbrnnkrq/pppppppp/8/8/8/8/PPPPPPPP/BBRNNKRQ w - - 0 1&quot;]
  </code></pre>
  <p><code>1. c4 O-O 2. Bxh7+ Kxh7 3. g3 Kg6 4. Kg2 Kh6 5. Kh3 Kh5 6. Rg2 Kg5#</code></p>
  <p>(@mods: can 960 be made playable - i.e. KQkq works in 960 FEN? If so, please edit and delete this comment)</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-08-27T08:24:55.447Z
Answers.LastActivityDate: 2024-08-27T08:24:55.447Z
Answers.UserDisplayName: Hauke Reddmann
Body: <p>What is the quickest way to get a checkmate under the following conditions:</p>
  <ul>
  <li>The winning side moves the king on every move</li>
  <li>The starting position is Chess960?</li>
  </ul>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-08-27T03:56:17.267Z
Comments.Text: Neither player can move the King in any Chess960 starting position, so this is impossible.
Comments.UserDisplayName: Allure
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-08-27T06:07:53.203Z
Comments.Text: In some positions, you can castle on move 1 in chess960.
Comments.UserDisplayName: Lucenaposition
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-08-27T07:44:35.577Z
Comments.Text: @Lucenaposition: True. This means especially only Black can do this: 1.wpawn 1...castles 2.longcat x bpawn 2...K x longcat. This reduces the number of 960 positions severely. I find that very interesting and give it a quick try, if I get bored, I sic MatPlus on it :-)
Comments.UserDisplayName: Hauke Reddmann
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-08-27T07:53:44.290Z
Comments.Text: EDIT: 8 moves suffice! This surely can be shaved, why I don't post it yet.
Comments.UserDisplayName: Hauke Reddmann
Tags: <checkmate><chess-variants><kings><chess960><construction-task>
Title: Checkmate with king moves only
ThreadText: # Checkmate with king moves only
  
  (Asked by: username_0 on 2024-08-26)
  
  What is the quickest way to get a checkmate under the following conditions:
  
  * The winning side moves the king on every move
  * The starting position is Chess960?
  
  **Tags:** checkmate, chess-variants, kings, chess960, construction-task
  
  > **Comments:**
  > **username_1**: Neither player can move the King in any Chess960 starting position, so this is impossible.  
  > **username_0**: In some positions, you can castle on move 1 in chess960.  
  > **username_2**: @username_0: True. This means especially only Black can do this: 1.wpawn 1...castles 2.longcat x bpawn 2...K x longcat. This reduces the number of 960 positions severely. I find that very interesting and give it a quick try, if I get bored, I sic MatPlus on it :-)  
  > **username_2**: EDIT: 8 moves suffice! This surely can be shaved, why I don't post it yet.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2024-08-27. Score: 10 | Accepted answer
  
  Pending a genius stroke from MatPlus, this might be the fastest way:
  
  ```
  [FEN "bbrnnkrq/pppppppp/8/8/8/8/PPPPPPPP/BBRNNKRQ w - - 0 1"]
  
  ```
  
  `1. c4 O-O 2. Bxh7+ Kxh7 3. g3 Kg6 4. Kg2 Kh6 5. Kh3 Kh5 6. Rg2 Kg5#`
  
  (@mods: can 960 be made playable - i.e. KQkq works in 960 FEN? If so, please edit and delete this comment)
  
  
  ---
  
  ### Answer by username_3 on 2024-08-28. Score: 3
  
  This problem can be solved computationally using the powerful "constraints" feature of Francois Labelle's Jacobi engine: <https://wismuth.com/jacobi/latest/solver.html>
  
  ```
  > option FirstToMove white 
  > stipulation h#6
  > condition Chess960 
  > constraint Xa8(0..0) Xb8(0..0) Xc8(0..0) Xd8(0..0) Xe8(0..0) Xg8(0..0) Xh8(0..0) Pa7(0..0) Pb7(0..0) Pc7(0..0) Pd7(0..0) Pe7(0..0) Pf7(0..0) Pg7(0..0) Ph7(0..0)
  > constraint Xf8!g8~
  
  ```
  
  A few comments:
  
  1. option "first to move white" implies also that black will
     deliver the mate. I.e. it's the equivalent of "halfduplex" option in
     Popeye.
  2. Jacobi handles variable officer positions using "X" to
     specify unknown unit. Castling counts as a king move, so 15 black
     units are prevented from moving by specifying their minimum &
     maximum number of moves as zero.
  3. We also say that the first move of the 16th unit is castling "!", followed by any number of other moves, "~".
  4. There are 360 solutions, all beginning "1.c3/c4 O-O 2.Bxh7+ Kxh7".
  5. 80% of the solutions follow the pattern given by username_2, however there is an alternative approach where White also castles: (BBSSRKRQ) 1.c3 O-O 2.Bxh7+ Kxh7 3.O-O Kg6 4.h4 Kh5 5.Kh2 Kxh4 6.Rg1 Kg4#
  6. There are 9 different game arrays that work, 2 first moves, and 2 final blocking moves by wQ/R. There are then various other duals which lead to 8+2=10. 9x2x2x10=360.
  7. There are no solutions in 6.0 moves with queenside castling.
  
  > **Comments:**
  > **username_2**: Now that's solving in style :-) Too bad for the immanent 1.c3/c4 dual, or one could make a "real" problem out of it. Point 6 doesn't surprise me, running to the border then takes too long, and a discovered check on an "epauletted" king (my 1st attempt) takes around 8 moves.  
  
  ---
  
  