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Expanded Chess. An attempt at a logical expansion of Chess to a 10x10 board.[All Comments] [Add Comment or Rating]
H. G. Muller wrote on 2023-09-16 UTC
Short castling seems to break the interactive diagram.

It seems to work for me. What exactly happens that you describe as 'break'?

NeodymiumPhyte wrote on 2023-09-16 UTC
Short castling seems to break the interactive diagram.

💡📝Daniel Zacharias wrote on 2023-02-11 UTC

I value thematic consistency, which is the only reason I added Zebras at all. Maybe I go too far with it at times. I do think they serve a functional role too by protecting the edge pawns. An Alfil-Zebra might be an interesting piece, but I wouldn't use it here because that would break the theme, unless the knights were made FN. I also don't want to have only very strong pieces; there are plenty of those already. I used zebras for aesthetic reasons; whether that choice makes for the best game, I cannot say.

H. G. Muller wrote on 2023-02-10 UTC

The AZ is a quite strong piece. It does not have mating potential, but is powerful enough to drive a bare King into a corner on boards up to 9x9. So it can pretty much checkmate in combination with anything. Even with an Alfil.

David Paulowich wrote on 2023-02-10 UTC

The Camel and the Zebra never seemed very useful to me. Combining a Camel and a Ferz gives us the Wizard which functions well in many variants, from Wormhole Chess to TenCubed Chess. I wonder if combining a Zebra and an Alfil would improve this game? Sample endgame provided below - the diagram has been cut down to six ranks.


WHITE wins by 1.Nc2 check Kb1 2.(Z+A)e3 mate.

H. G. Muller wrote on 2022-05-29 UTC

The Checkmating Applet cannot do bent riders like Osprey. But it can do a truncated leaping version, like DC. And a pair of these does have mating potential, on 10x10. In the theory of 3-vs-1 mates discussed on the Applet page the Osprey would classify as 'potent', since it can switch its attack from c1 to a1 in a singly move (e.g. f2-f4 or f2-d2). This means it can execute mates in combination with almost anything else that is not bound to the same color.

In fact an Osprey can drive a bare King into a corner together with almost anything on any size board: positioned on an edge it can dynamically confine a King in a corner with the help of its own King. With moves to spare, which can be used to invoke the additional piece.

Jean-Louis Cazaux wrote on 2022-05-29 UTC

W^B is referred as Manticore on CVP. An Aanca is F^R, Gryphon here. This is an old tiring discussion.

Kevin Pacey wrote on 2022-05-28 UTC

As far as I can tentatively estimate, on 10x10 an Osprey (D^B) would be worth about the same as a W^B (referred to by Betza as an Aanca, in his article on evaluating Bent Riders, at least)).

It would be interesting to know, if the Osprey piece type were to be used in a later CV (e.g. a 10x10 one), where stalemate is considered only to be a draw, whether king plus two opposite-coloured Ospreys could generally force checkmate vs. a lone king. I've already imagined at least one mating situation being possible.

Carlos Cetina wrote on 2020-11-21 UTC

It seems that the sissa-arx-2020-246-116 log is broken, however I happened to discover a strange way to recover it by clicking on the small rectangle below the promotions menu.

💡📝Daniel Zacharias wrote on 2020-11-20 UTC

I had tried that before and had trouble defining moves or promotion or something, but I just tried again and was able to make it work. Thanks!

H. G. Muller wrote on 2020-11-20 UTC

Have you tried generating the GAME code with the Play-Test Applet? This should have no problem with a castling where the King ends at the Rook location. (As of today; I noticed there was a bug there in taking back the castling, because the Rook and King were put back in the wrong order, so that the King would turn into a Rook during the legality test.) I temporarily changed the castling rule in the Mighty-Lion preset to do 3 King steps, and this works fine even for K-side castling.

💡📝Daniel Zacharias wrote on 2020-11-19 UTC

Apparently that wasn't as easy as I thought since it didn't detect whether the king would pass through check from new pieces, which I also don't know how to fix.


I think I found a solution by modifying the fairychess castling subroutine to move the king and rook one space over after castling. It highlights the h2 and h9 squares for moving to instead of i2 and i9 but it works.

💡📝Daniel Zacharias wrote on 2020-11-18 UTC

I'm trying to figure out how to get the castling rules enforced properly. I really don't understand what I'm doing. Based on this preset I managed to include the fischer file and make the proper castling moves display as legal, but when I try to actually castle it says You cannot capture your own pieces. I think this has something to do with the post move sections but I'm totally lost trying to understand what needs to be changed.

💡📝Daniel Zacharias wrote on 2020-11-13 UTC

yes, that's correct

Jean-Louis Cazaux wrote on 2020-11-12 UTC

Daniel, I programmed your variant on Zillions to see how it looks. I was wondering if the castling done by moving the King 3 steps towards the Rook on both side is intentional? On King's side it means that the King goes on the Rook square. Is that correct?

💡📝Daniel Zacharias wrote on 2020-11-12 UTC

I'd be interested in reading more about the major/minor pieces too, as well as conjugates. I was aware of that concept but didn't know there was a term for it.

The added pieces in this game are meant to correspond to the rook, knight, and bishop, and relate to each other in the same ways those three do. That's why I chose the zebra rather than camels or something else. The knight switches colors so it's counterpart should too, and the zebra's moves are one diagonal step out from a knight's, just as the gryphon's are from the rook's. Also the zebra leaps to the nearest opposite colored squares outside the combined gryphon and osprey moves, like a knight does with the rook and bishop. I don't know if that's a good way to design a game, but I like the completeness of it.

Is there a good word to describe the relation the gryphon has to the rook? The closest I've thought of is expansion.

H. G. Muller wrote on 2020-11-12 UTC

Thank you, I will think about it. Perhaps I could expand it with some diagrams, or even with links to the Checkmating Applet preconfigured for the mentioned pieces, so that people can try it out immediately.

My main problem is that I am afraid that no one would find such an article, unless they accidentally stumbled on it. (Which, considering the number of articles we have here now, is not very likely.) An alternative is that I would add it to the Checkmating Applet itself, just like I added some general theory on how to checkmate with a pair of minors to the 3-vs-1 Checkmating Applet.

Jean-Louis Cazaux wrote on 2020-11-12 UTC

Very good explanation of major / minor notion. Your answer would deserve to be presented as an article on this site.

H. G. Muller wrote on 2020-11-11 UTC

I think the consensus definition of 'major' is a piece that, together with its own royal, can in general force a win against a bare royal of the opponent. Pieces that cannot do that are 'minors'. In orthodox Chess the situation is clear: R and Q are majors, B and N are minors. Accidentally this correlates perfectly with piece values, but this doesn't have to be the case in general. The lowest-valued major I could find on 8x8 is a leaper with only 5 moves (the Deva, fFbrFfWlW, from Maka Dai Dai Shogi), which in a FIDE context probably would not be worth more than 2 Pawns. Minors can be more valuable than a Queen. (Think of a color-bound universal leaper, which can teleport to any dark square.)

It of course depends on how the royal moves: in Knightmate a Rook is a minor. Board size matters too: a non-royal King is a major up to 14x14, but a minor on 15x15. And on a cylinder board the Rook is a minor. The stalemate result also matters: in Xiangqi even a Pawn is a major.

It can also be a bit obscure what 'generally won' means. A piece that moves as Rook in one dimension, and as Dababba in the perpendicular one (e.g. vRsD) has mating potential on any size board, except that on even-sized boards there is a fortress draw when the bare King is on the edge that the piece cannot reach. So it depends on whether you can cut off the King from reaching that edge. With the perpendicular move a Dababbarider (vRsDD) you have even better chances to achieve that, and a relatively small fractions of the possible start positions is draw. (But many more than the 0.5% or so that you typically see in a generally won end-game.) With the weaker majors, such as the range-2 Rook, there are also drawn positions where the R2 is cut off from its King, and 'dynamically trapped' in a corner area by the bare King on the same diagonal. There is then no way to outflank the King; it can always get on the diagonal where the R2 moves to, and will approach and eventually attack it when it doesn't move. So I guess in general there still is something like a continuous spectrum between minor and major.

Jean-Louis Cazaux wrote on 2020-11-11 UTC

I understand now what you call "conjugate". Interesting notion. I've looked with ZoG what it says about W-then-B, N-then-B and D-then-B (the Osprey here). Like you said, it estimated the Osprey slightly stronger than a Rook on a 10x10 board. On a 8x8, it gives the Rook slightly stronger than the Osprey.

Another question HG, how is defined a major or a minor? It's still obscure for me. Thank you.

H. G. Muller wrote on 2020-11-11 UTC

Not wrong, because 'counter-part' is a more loosely defined term than 'conjugate'. The latter I have seen only used in the meaning I gave previously. Basically, the conjugate piece is what you get when you grow a new diamond-shaped square in every square corner of the board. Which means it is not a symmetric relation: The Ferz is the conjugate of the Wazir, but the conjugate of the Ferz is the Dababba. The Camel is the conjugate of the Knight. Conjugates by definition are color bound. The conjugate of the W-then-B would be the F-then-DD (as the conjugate of B is the Dababbarider)

In XBetza notation I introduced the term 'rotation' of an atom, which is a symmetric relation: F is a 45-degree rotated W, and W is a 45-degree rotated F. Similarly A <-> D and R <-> B on rotation. So I guess one could say the Gryphon is the rotated 'Rhinoceros', and vice versa. The large Shogi variants often employ this 'playful symmetry', where pairs of pieces in mirror-image positions of the setup interchange orthogonal for diagonal moves of the same range, and vice versa.

I used this W-then-B in my variant Team-Mate Chess, because it is a quite strong piece without mating potential. (And the design goal of Team-Mate Chess was that it would always require at least a pair of pieces to beat a bare King.)

Jean-Louis Cazaux wrote on 2020-11-11 UTC

Oh thank you HG, my mistake! So, the Osprey is a colorbound piece. Interesting.

My preferred "x-then-bishop" is a 3rd one, W-then-B that I use in some of my large variants (I call it Rhinoceros). The Gryphon/Eagle being F-then-R, I see that pair as counterparts, am I wrong?

H. G. Muller wrote on 2020-11-11 UTC

Note that the Osprey is not the same as the Grant-Acedrex Unicorno. It is D-then-B, while the Unicorno is N-then-B. The Osprey is the 'conjugate' of the Gryphon, i.e. it has the same move as the Gryphon on the 45-degree rotated grid of squares of the same color.

I agree that this seems a very nice game. And perhaps it would benefit from a pair of Camels as extra minors, to better balance the addition of the quite strong Gryphons (which are close to Queen in value). Even the Osprey seems stronger than a Rook on this large board (even though it formally also is a minor).

Jean-Louis Cazaux wrote on 2020-11-11 UTC

Maybe, I would have added a pair of Camels, leaping (4,2), to fill c1 and h1. They would fit well the spirit of this game.

Jean-Louis Cazaux wrote on 2020-11-11 UTC

Interestingly this variant put 3 additional pieces on the decimal chessboard, 3 additional pieces that are, as the matter of fact, old known pieces! Indeed the 3 of them are found in the Grant Acedrex from King of Castile Alfonso X's codex published in 1283.

The Gryphon is the Aanca of the Spanish text, an Arabic word designating an "Elephant Bird", a very big legendary eagle of the oriental tales, able to carry an elephant. Murray translated, a bit wrongly, as a Gryphon (which is another legendary animal).

The Osprey is the Unicornio of the Spanish text, which according to the original illustration designated a Rhinoceros. Consider that in 1283 not a lot of people new what a rhinoceros was and it was identified with the legendary unicorn. I like the idea of a Rhinoceros for this piece that goes deep inside the opposite defensive lines.

The Zebra is the Zaraffa of the Spanish text, obviously a Giraffe, considering that, again in the 13rd century, this beast was a bit frightening for those who had the chance to have seen one. Murray and some others after him had another interpretation of the described move, a step (5,2) instead of a step (4,3) which was a misunderstanding.

I also use Eagles, Rhinoceros and Giraffes in Zanzibar but on a 12x12 board.

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