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Nice page and nice diagram
Greg Strong wrote on Mon, Jan 2, 2023 02:33 PM UTC in reply to Jean-Louis Cazaux from 12:10 PM:Yes, nice page. I have published it.
📝H. G. Muller wrote on Tue, Jan 3, 2023 09:54 PM UTC:I made a first attempt to make the Diagram play this. At the moment it still doesn't know the rule that you cannot leave the Duck where it is, although it effectively enforces that rule on the opponent, because its moving is triggered by moving the Duck.
This simplification makes it possible to treat it similar to Refusal Chess: the search just keeps track of the two best moves (in absence of the Duck), and only uses the score of the best if that is a contact capture (assuming the Duck would block it otherwise). In Refusal Chess you would always ignore the best move, assuming it will be refused. A refinement is that moves that have the same blocking square as the best move cannot become second-best (because then both could be blocked simultaneously). It only considers blocking on the first step of a slide, so it will overlook 'cross blocking' (where the Duck would block two moves going over the same square in different directions, and these happened to be best and second-best).
It will also overlook the possibility of 'reserving' your next move, as this cannot be done when moving the Duck is not mandatory. This will be hard to implement without making it very complex. Only moves with a single blocking square can be reserved, and it only makes sense to reserve a move that would refute the opponent's best reply to your current move. This would be an alternative method of 'disarming' his best move, which can be used when it is not possible to block that move. If it was blockable, so that both methods are available, it would make no difference which method you used, as both would make him fall back on his second best move. Unless the move you reserve refutes that move too. The chances that several moves are refuted by the same (reservable) move are a lot larger than those that you can block several independent moves (i.e moves that are not part of the same slide): you only need a hefty threat (like a check), and most of his moves are out. It must be possible to design a not-too-complex algorithm based on that idea.
📝H. G. Muller wrote on Thu, Jan 19, 2023 09:49 AM UTC in reply to H. G. Muller from Tue Jan 3 09:54 PM:The AI of the Diagram now also understands the trick of reserving a square for your next move by playing the Duck there, as you can verify by setting up a position through h7-h6, g7-h4, h2-h3, Ke8-h5, Qd1-d3. If at that point you switch on the AI, and play a useless move for black (e.g. a7-a6, Duck to a7), the AI will reply with Qf5, Duck to g5, and announce mate. (Which in this case does not end the game yet, but should be interpreted as announcement of King-capture in 2. In general the Diagram will allow you to play on when you are checkmated; if you do a pseudo-legal move there it will capture your King an announce "I win".)
Anyone can play Duck chess online on https://www.pychess.org as well. https://www.pychess.org/news/Duck_Chess
📝H. G. Muller wrote on Wed, Feb 1, 2023 11:27 AM UTC in reply to Tamás Bajusz from 11:22 AM:Thanks for the info. I added the link in the notes section.
While playing this, it let me castle while in check. Here are the moves:
- e4 Dd6
- c5 Dc7
- Bc4 De6
- d6 Dd7
- Qf3 De6
- Nf6 Dd3
- Nc3 Dd7
- h5 Dd3
- Nd5 De6
- Nbd7 Dd3
- Ne2 Dc7
- Nxd5 Dg4
- Bxd5 Df6
- Ne5 Dg4
- Qf4 Dd3
- e6 Dc4
- Bxe6 Dd3
- Bxe6 Dg1
- Qe3 Df3
- Nc4 Df4
- Qd3 Dd5
- Ne5 De7
- Qb5 Dd7
- Nc6 Db6
- d4 Da6
- Qb6 Dxd4
- Qxb6 Dd8
- axb6 Dg1
- Bg5 Df6
- Nb4 Dg1
- c3 Dc2
- Nd3 Db8
- O-O
The Rules say here that "There is no check in this variant."
Back on 2005-03-08 a BLOCKADE STALEMATE IN 20 MOVES was posted on the SHATRANJ rules page. I believe that a similar stalemate can be achieved here in 15 or 16 moves. See the diagram below.
The White Rook previously captured a Bishop on (a6). After capturing a Knight on (e6) and moving the Duck to (g6), the game ends with a stalemate (and Black wins).
📝H. G. Muller wrote on Sun, Nov 5, 2023 08:03 AM UTC:True, but why would white move the Duck to g6, if moving it anywhere else would force black to sacrifice his King? If white wants to lose he could simply resign. So from a game-theoretical POV there is no extra move option here.
Would letting Black place the duck after his first move provide a more balanced game?
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OK, I created a Duck Chess page. I think it is ready for publication, but even though I am an editor I consider it bad form to publish my own articles. So perhaps another editor could judge it.