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Another variant which may be better than Heisei.

http://pika.cs.nctu.edu.tw/lit/MillenniumShogi.rar

One modern variant of Chu Shogi, called Millennium Chu Shogi(¤d¦~¬ö¤¤±N´Ñ), is played on a more open board. 40% of the pieces are set aside at setup and held in reserve. Once during the game a player may drop one of these on any empty square as long as at least one friendly piece now stays in the enemy camp(promotion zone, the farthest four ranks of the board); otherwise only drop on his own camp(the closest four ranks of the board).  If dropped into the promotion zone, the piece must dropped as its promoted piece.

The set-aside pieces are the Lances, Coppers, Silvers, Side Movers, Vertical Movers, Reverse Chariots, Kyrin, and Phoenix. 

Captured pieces do not come back into play, and the rest of the game is played as in regular Chu.

I wrote an engine (called HaChu) that can play Chu Shogi under WinBoard (the Alien Edition, as it needs multi-move support for the Lion). The idea is that in the future it would also be able to play the even larger Shogi variants Tenjiku, Dai Dai, Maka Dai Dai and Tai. But currently it plays only Sho, Chu and Dai Shogi (and Shatranj and Makruk, which are very Shogi like). I packaged engine and GUI together in a special Chu Shogi release. It can be downloaded from

http://hgm.nubati.net/WinBoard-Chu.zip .

WinBoard uses mnemonic piece pictograms in board sizes 'tiny' and 'petite', and traditional kanji in other board sizes. (Your OS must have Asian language support for that to display correctly.)

The engine is pretty strong (but you can always handicap it by hefty time odds). I played it on the 81Dojo server, and is able to compete with the strongest Chu players there.

I declared the HaChu engine to be open source, so that it can be supplied by Debian for Linux. This begged for a Linux interface that could handle Chu Shogi, and unfortunately the 'mnemonic piece set' shown in the previous (Chu Shogi) comment is only implemented in WinBoard.

For XBoard I therefore used a representation with pictograms, (which a poll showed to be highly preferred by Chess players, despite their inferior neature), using as many of the 22 piece symbols that were already supported by XBoard. (But this was barely enough for the pieces in the initial setup. So I had to make some extra symbols for the promoted pieces, which are mainly slightly modified versions of the unpromoted piece that moves the same.

This is what I finally settled on:

Laziness prevailed in the cases of Blind Tiger (using the masked Horse that normally represents Nightrider), Reverse Chariot (using the Canon) and Go Between (using the Cobra); for the rest I am reasonably happy with how the unpromoted pieces look. The only new symbols used in the initial setup are the Lion, Ferocious Leopard and the standing and lying sword. The latter three were used in stead of XBoard's existing Falcon, Unicorn and narrow crown of the Grasshopper symbols, because the latter seemed more apt for designating some promoted pieces with unique gait. And swords seemed a very useful representation for the Vertical and Side Mover, as the way they point reminds you of the move pattern. (A similar argument led to the existing crosssed-swords symbol (the 'SMIRF' Archbishop) to represent the Phoenix, and the more roundish U.S. Marhall star to represent the Kylin.)

In the above picture the pictograms can be characterized as follows:

S . . S . S . . .
S . e e C C . C L
S . e e C C S S .
. . e e S S . . c

That leaves 14 new pieces that would have to be memorized (the Elephant counted double). If you already have used XBoard for Shogi, that is.

The CVP have received an email with a link to a "modern large shogi variant that seems to adapt chu shogi in ways that your readers may find appealing".  The page is in Japanese:

http://seesaawiki.jp/nari_shogi/d/%BC%EB%BF%FD

This is indeed an interesting 11x11 variant, which at first glance seems a cross between Sho Shogi (9x9) and Chu Shogi (12x12). It shrinks the board compared to Chu Shogi by eliminating the duplicats of Bishop, Rook, Horse and Dragon, and having only one of these each.

On closer inspection there are quite some extra differences, though. The Ferocious Leopards of Chu are replaced by (Shogi) Knights from Sho Shogi, which then promote to FL. The Pawns are really 3 different kind of Pawns, the ordinary kind that promotes to Gold, but also those that promote to Silver or Copper. Gold promotes to Bishop rather than Rook.

There also seem to be differences in the way pieces move. The Blind Tiger seems to move like an inverted Silver (not sure if it is still called a Blind Tiger; my reading of the kanji is not that good), and their promoted form ('Flying Stag') does lack the sW moves. Also the pieces to which Dragon Horse and Dragon King promote (Horned Falcon and Soaring Eagle in Chu) now move different, and seem to have the double-move sting in 4 directions in stead of 1 or 2 directions, respectively.

The Lion does not seem to be a Chu-Shogi Lion, but a piece with a 'sting' in 8 directions, which promotes to 'Vermillion Sparrow' (which moves as Chu Lion?). The Free King also promotes, (to Golden Bird, and I am not sure how that moves). The King promotes to an 'Emperor' (?), which is not like the Maka-Dai-Dai Emperor, though, but a KD.

I have a question for Adrian King.
I hope he reads here.

On Roger Hare's page, you are credited for the promotion rule, "if one of your pieces does not promote on the turn on which it enters the promotion zone, then that piece may not promote on your next turn unless it makes a capture on that turn. On subsequent turns, however, the same piece may promote whether it makes a capture or not, provided that it makes a move partly or entirely within the promotion zone".

I would be interested in knowing the origin of this rule, in particular the idea that promotability on non-capture would regenerate after ONE TURN. This is different from the rule described in George Hodges' Middle Shogi Manual, which states that such promotability only regenerates by MOVING THAT PIECE. This again is different from the current rules of the Japanese Chu-Shogi Renmei, which specify that the piece would have to leave the zone first. (In other words, non-captures can only promote when they enter the zone from the outside; moves entirely in the zone or leaving it can promote only if they are captures.)

So it seems there are three different versions of the promotion rules for the historic game.

Chu Shogi has never been "the dominant form of chess in Japan", let alone "for centuries". This is perhaps a mistake caused by confusion with Sho Shogi (Small Shogi), the 16th century name for the predecessor  of Modern Standard Shogi (still without drops), to distinguish it from Dai Shogi (Great Shogi) and Chu Shogi (Middle Shogi). These larger games were popular, but Sho Shogi was the dominant game, even before the introduction of drop rules. Also Chu Shogi is the youngest of the three (15th century), it didn't even have the time to be dominant for centuries, for at the beginning of the Edo period (around 1600)Standard Shogi, promoted by the shogunate, began to oust the larger forms, even though many large variants were invented (and certainly played) at this time

I don't know where you got that from. According to my information, Chu Shogi was already mentioned in manuscripts dated as early as 1350AD. A diary entry from 1424AD mentions a Shogi match played in front of the emperor, where one of the players was handicapped by a Free King. So that was certainly not referring to Sho Shogi. It was apparently considered so evident that 'Shogi' would mean Chu Shogi that the qualification 'Chu' was omitted. Tsume problems dating from 1675AD, 1697AD and 1746AD are all Chu Shogi problems; no historic problems or game records from Sho Shogi are known from that period or earlier.

All this is described in the Middle Shogi Manual, which was compiled in cooperation with the research group on the history of Shogi at the University of Kyoto. What are your sources?

If that's the Manual written by Hodges, I do know it. And you are RIGHT when you say it is first mentioned 100 years EARLIER than I claimed. I apologize. That makes it still younger than Sho and Dai Shogi EXCEPT when you argue that the Heian Dai Shogi was really a kind of Chu Shogi and The later Dai Shogi was the novelty. Dunno, you tell me!

But that the Yamashina family had a faible for Chu Shogi is meagre evidence for Chu Shogi ever being more popular than the smaller variant. On the other hand  the carpenter Minase Kanenari tell us  that between 1590 and 1602 he produced 618 sets for Sho Shog but only 106 sets for Chu Shogi (that's from the web). That also doesn't prove very much. Or does it? But I admit, I just thought that it was commonly accepted among scholars that at least in the 16th century and later Sho Shogi was dominant, and for earlier times we lack proper information. I never claimed Chu Shogi was not a popular game. Just that Sho shogi was more so.

I think when Hodges states, that Chu Shogi was the more popular game in the Kamakura period he overstretches the (few)sources we have about the game in this time. Historians do that very often. You should always reckon with that and being published by a University unfortunally does not prevent them from doing so. 

That the first tsumes and game scores come from Chu- rather than Sho Shogi I really doubt. But i cannot argue against, for I'm on holydays and the web is a very bad source for chess history. If it is right I would be very surprised.

Do you mean the game scores of Yamagata? But they are composed games, aren't they? The first scores of really played games i know are from the early 20th century, but i don't remember where i have that from.

Do you know the earliest game scores of Standard Shogi? I don't!

I was referring to the games Mori-Fukui, Kondo-Konishi and the handicap games Kuri-Masuda, Kuri-Sawada, and Mori-Matsumoto (2x). These are recorded in a manuscript from 1778, but it does not say when the games were played. The 50 mating problems by Ito Sokan I were published in the Chu Shogi Zushiki from 1697AD.

The MSM doesn't mention they are compositions. Why would anyone compose complete games? And even if they were, because people in those days would have such a strange hobby, it doesn't seem to make it less significant they composed Chu rather than Sho games, instead of playing them.

The MSM further states: "By the time of the Northern and Southern Courts period in Japan (1336-1392), Middle Shogi, played on a
board with 12 squares each way and with 46 pieces on each side, had evolved. In subsequent years it
enjoyed considerable popularity and our first clear record of the game dates from 1350." 'Record' here must not mean 'recorded game', but just a reference specific enough to recognize it unambiguously as Chu rather than Sho or Dai Shogi.

First published description of moves and rules is claimed to be the book "Aro Kassen Monogatari", volume 4, by prime minister Ichijo Kanera, dated 1476.

I believe you that they are actually played games. But you probably know that most of the extant game scores of European chess prior to the 19th century are composed games, especially in handbooks written to teach the game (for example ALL games of Greco are compositions). Also the oldest extant game scores of Chinese Chess are from such handbooks and are assumed to be compositions. So my assumption was not THAT farfetched. I do not know though if this "strange hobby" as you call it was common in Japan also.

And again, I never denied that Chu Shogi was a popular game. But I'm still not convinced that it ever was more popular than the smaller one.

So from which time are the first extant Sho Shogi game scores? Do you know that?

> So from which time are the first extant Sho Shogi game scores? Do you know that?

No, do you? You still haven't told me your sources.

BTW, just looking at the game suggests Sho Shogi would not stand a chance to rival Chu in popularity. Compared to Chu it is as dull as Shatranj is compared to modern Chess. In addition all historic variants seem to be based on Chu Shogi, and evolved towards larger size. If people would have thought the smaller game was better, you would have expected them to make variants based on Sho.

No I do not know any game scores of standard Shogi prior to the 19th century. And that's quite strange.

You must understand, true, I am not really sure about the situation in the Heian and Kamakura period. But in the Edo era, from the end of the 16th century on, if somebody said "Shogi" he meant the game on 9x9 squares. If he meant another variant, he had to specify. It was the most prestigious game in Japan after Go, which was - of course - the game of games. Shogi - the 9x9 game  - was promoted by the Shogunate, the government. Like in Go, the official title of Meijin for the best Shogi player was established and the annual castle tournaments were held, in the presence of the shogun or even the emperor, I'm not sure. At this time the names of the first great players are known. They all played the 9x9 game, not the bigger variants.

My sources? Are you kidding? That's so basic knowledge, you cannot dive into the history of Shogi for one afternoon without knowing that! 

And now to your statement about Standard Shogi and Shatranj being "dull" games and that just having a "look at the game" of Chu Shogi  suggests Sho Shogi would not stand a chance to rival Chu in popularity." and so on...

Now I have NO opinion at all which one is the "better" game. But you have disqualified yourself so much stating such a nonsense, that I really think that you do not know ANYTHING about what you are talking and just arbitrarily pick it from the web, and actually I do not feel like replying to you any more. Sorry, bro.

BTW, just looking at the game suggests Sho Shogi would not stand a chance to rival Chu in popularity. Compared to Chu it is as dull as Shatranj is compared to modern Chess.

This is a subjective claim, and Spengler Georg is right to criticize you for it. Saying something like this just doesn't prove your point. Besides that, the complexity of the game is a strike against it. Popularity is about numbers, and more people are likely to play a game in greater numbers if it is easier to learn.

In addition all historic variants seem to be based on Chu Shogi, and evolved towards larger size. If people would have thought the smaller game was better, you would have expected them to make variants based on Sho.

This is a more compelling point, though it will require some demonstration, and it still doesn't prove that Chu Shogi was more popular. Furthermore, modern Shogi is apparently a variant of Sho Shogi, and that became the most popular Shogi variant in modern times.

If Sho Shogi was more popular, then it followed the same trend seen in China, Korea, and the west of the most popular variant being a game of around the same size with similar pieces, and it better accounts for modern Shogi being more popular today than Chu Shogi is. But if Chu Shogi was the more popular game, it is the exception to the rule, and we are left wondering why its popularity declined in favor of a very different game. So it looks like the default position is that Sho Shogi was the more popular game, and if you want to claim that Chu Shogi was more popular, you will need hard evidence to back this up.

Well, I have given the reference to the hard evidence: the Middle Shogi Manual compiled by George Hodges in collaboration with the research group at Kyoto. It contains the references to the historic sources on which it bases its conclusions, which I have paraphrased here. The sources themselves are of course all in (archaic) Japanese, which I cannot read at all. But I have no reason to doubt Japanese academic research on this. 

In fact I have a lot more confidence in Japanese academic research than in some western clown that 'just knows things' without being able to tell where this knowledge comes from, and then blames others for his ignorance. But everyone can of course decide for himselve whether he rather believes a Japanese history professor or a bragging westerner, on matters of japanese history.

And the 9x9 game of course became only popular after the introduction of drops. That transformed it from the boring Shatranj-like game to the fast and exciting game Shogi is today.

Yonin Shogi is a 4-player variant of modern Shogi, so I suppose you mean a 4-player variant of Chu Shogi here.

I don't think that this would be a viable game. Multi-player versions of Chess are troublesome, because there is every incentive to not get engaged in battle: even if your tactics gain material compared to your victim, you in general lose compared to the idle by-standers. This does no longer apply when winning a battle actually gains you someting on an absolute scale, as it does in games where captured pieces can be dropped as your own.

So it is the drops that make Yonin Shogi an interesting game. And Chu Shogi has no drops. Of course you could allow drops in the hypothetical Yonin Chu Shogi, but Chu Shogi with drops is in itself troublesome, because of the very wide strength range of the pieces. I guess this could be fixed too, but if you change too much you will get a game that has so little resemblance to Chu Shogi that it would only be confusing to call it Yonin Chu Shogi.

Dr Muller, I read your very intriguing presentations of errata in the tsumechushogi problems from collections A, B, and C published in Middle Shogi Manual.  I have to wonder whether there are errata in collection D that your analysis has revealed and whether you would think such fine studies worthy to add to CVP.

@Bukovski:

Yes, I used my Chu Shogi engine to solve all 224 problems of the A-D series,or prove no solution exists. Series C and D were different from A and B in the sense that the historic documents from which they came containedno solutions. So all problems that were solved when the MSM was published were solved in recent times, and many were still unsolved. Of the latter, 14 problems of the D series could be solved, while18 were proven flawed.

So far I did not put the results of the D series on-line, to keep open the possibility to use them in contests. (I thought I had done the same with the C series,but apparently not.)

I put together my own Chu set based on the mnemonic pieces, by simply cutting their shapes from stickers, and stick those on Draughts chips. Two Draughts sets of 2 x twenty 35mm chips were used for the (32) pieces, while a set of smaller (29mm) chips was used for the Pawns and Go Betweens (14 chips used). The required board is 42 x 42 cm, and was simply drawn on four sheets of A4 paper.

Can someone please help me with a question regarding this rule?  I need an answer for a game in progress...

A Lion cannot capture a Lion if that would expose it to recapture in the next turn, as if it had become an absolute royal for one turn. ('protected')

My question is this: can a Lion make a 2-step move in which he captures the other Lion (which is protected!) with the first step, and then move to safety with the second step?

Thanks!

Yes,it is always allowed to capture an adjacent Lion. Even if it means your Lion can be recaptured afterwards.(Which you usually of course can and want to avoid.) In this case the recapture would also be legal.

Ok, next question:

If a Lion captures the opposing protected Lion by means of capturing a second piece first, is it then permissible to recapture the Lion, or does this rule prevent it?

A non-Lion cannot capture a Lion when on the previous turn a Lion was captured by a non-Lion on another square.

It sounds like this rule prevents it, but that seems crazy. 

The rule does not apply to your case for multiple reasons:

• It specifies what happens after a non-Lion captured a Lion, while your case starts with a Lion capturing a Lion
• The rule applies to what happens when the Lions are captured on different squares, while in your case the two Lions are captured on the same square.

So neither the protected-distant-Lion nor the counter-strike rule apply to this case, which by default means the recapture is allowed. There even is a special Japanese term for this, which translates as 'beating/shooting the Lion'.

BTW, the addition 'on another square' is there to handle the unique case of a Kirin (a non-Lion) capturing a Lion and promoting, so that the recapture now hits a Lion too. Recapture of this Lion would be allowed, while a counter-strike against a Lion elsewhere with a non-Lion would be forbidden.

Here's a set I made earlier so if people are looking for cheap ways to make a chi shogi set here's an idea. I drew the board but you can also use a 13x13 go board too. The counters cost me about £1.50? And I just wrote on them with sharpie.

It looks like you used a fake URL for your image. It literally says "fake-url" in it.

Oh it looked fine from my iPad? I pasted a photo into the comment. Is there a better way to do it?

Click on the image button and enter an URL to the image. It's to the right of the flag (Anchor button) and to the left of the graph (Table button) in the right center part of the top row. Or go to Source mode and directly enter HTML in the form of

<IMG SRC="image-url">

If you want to have the images hosted here (if they are just on your computer, not on the web yet and so have no URL), send them to me and I'll put them into the folders for the respective games.  (The text editor doesn't support uploading of images, AFAIK)

Here's a set I made earlier so if people are looking for cheap ways to make a chu shogi set here's an idea. I drew the board but you can also use a 13x13 go board too. The counters cost me about £1.50? And I just wrote on them with sharpie.

Hi,

I don't know if anyone has mentioned this yet, but the chu shogi preset is not working; I had a look, and the { } 's in the FEN code seem to have been replaced with their charachter codes, and when you click 'menu' from an already active game it seems to use the chess FEN code. I can't edit it because I didn't make it and the FEN code can't be changed via customize.

Would someone be able to check it out?

Thanks in advance!

sxg

These are mere presets that do not include settings files. I edited the HTML forms for the Chu Shogi presets to use FEN code that has not been URL encoded.

Dr Muller, you mention the bare king rule as used by the Nihon Chu Shogi Renmei, but I have to wonder if your computer analysis has revealed what pieces singly or in combination are sufficient to force or at least deliver checkmate on a bare king in chu shogi.

Only Pawn, Leopard and promoted Leopard cannot not force checkmate on a bare King. Many of the weak pieces lack mating potential, but against a bare King they should be easy to promote, and all promoted types except Bishop have mating potential. Because they virtually all have at least one orthogonal sliding move, and can move perpendicularly to that. That is all that is required, and makes the mate in fact quite easy (so that last century even a mechanical machine was built to do it!). The other exceptions are +P and +DE. As it turns out, Gold has no mating potential on 12x12 (it stops at 11x11), but DE and +DE still have (up to 14x14, IIRC, which would affect Dai Shogi). A Blind Tiger that cannot seek shelter with its King can sometimes be chased by the bare King to its back-rank, and get lost there. And Pawns approached from the front are doomed too, if the bare King gets there before yours.

The only pair of pieces without mating potential is a pair of +FL on the same 'square shade'. Provided none of them is trapped, which for two Pawns far away from each other can be a problem.

@Dr Muller: You had mentioned that you had analyzed the D document of historic chu shogi problems in MSM, had reserved the results of your analysis, and had concluded that 18 were proven flawed.  I wonder if you had reached a conclusion about the 18 like one that Mr Hodges proposed about the D document generally, that necessary pieces possibly had been omitted or erroneous pieces introduced into the diagram to act as a security device against plagiarism.  I read your suggested corrections to problems in the other 3 collections; I do not ask you to divulge more than you want about D, only to ask if your research suggested that the flawed problems might be fixed by the removal, change, or addition of pieces to the diagram.  Kind regards!

I have not really looked at those problems to see if I could find an easy flaw since I first analyzed them, and have been busy with other projects since.It seems a daunting task to figure out if the lack of a solution is due to a plausible oversight of the composer, and what he overlooked. I am not even sure how one would have to approach that problem. The computer just concludes whether there is a mate or not. It doesn't know the concept of 'nearly mate'. Because all the moves are checks it is not uncommon in problems that do have a solution that there is only a single legal move for gote in some positions, or only a single move that does not get him mated very quickly. So having only a single move to escape the mate in some variation doesn't really indicate the composer must have overlooked that move. (Ignoring the problem that the computer usually does not know there is only one refutation to the mate attempt, as it doesn't search any alternative moves once it finds the refutation. This could be solved by altering the program to require at least two refutations in each position, at the expense of driving the solution time up by a factor of 2^N for a mate in N full moves.)

It really requires human judgement to identify a move as a plausible candidate for being overlooked.

Perhaps the following would work: equip the program with a 'conditional exclude-move' option, through which you could tell it: in this position, you must consider that particular move as illegal. You could then start running the engine on the the flawed problem; it will find a principal variation that keeps up the checking as long as possible, but eventually it will run out of checks. You can then try to 'repair' the problem by 'outlawing' the gote moves in this PV one by one, starting at the end, and try to solve the problem for that case. If the outlawed move was the only move that escaped mate, the problem would then have a solotion, and the defensive move could have been the one overlooked by the composer. If the problem is still flawed, because gote has an alternative escape, we probably are already in a position that was never intended to occur.

About the strategy part of the article.

From the games I had played against user Dax00 it seems to me the advices here are not optimal although wikipedia states roughly the same things regarding the early moving up of steppers.

In our games dax00 has taught me to early lyon jump in front very early (the latest at turn 3) and then the stronger pieces take relevant forward positions until it becomes worthless for them to keep dancing around, and only then steppers (and maybe phoenix) kick in slowly but surely as the strong pieces are stuck in their duties :)!

What am I missing?

Getting a Lion out early is OK; it is impervious to stepper attack by its igui capability, and can easily withdraw when chased by sliders because of its jumping ability. And if the opponent develops his Lion, you often have no other way to keep it at bay than opposing it with your own Lion.

But suppose your opponent will keep his sliders safely behind his Pawn wall, and advances his Copper, Silver and Leopard while you are dancing around with your sliders. No matter how fast you develop your sliders, they won't be able to breach the Pawn wall, as this is well protected by the opponent's sliders without him having to spend many moves: his sliders start there. At some point the Silvers and Coppers stream out through the occasional hole in the Pawn wall, and will start forking your valuable sliders, which are trapped in the narrow area between the Pawn walls (usually both sides advance all their Pawns one step without opening up large holes, to allow the Side Movers to cover the original Pawn rank). You will get slaughtered.

Sliders are very valuable in Chu Shogi, because they promote easily in the end-game. Promoting steppers, OTOH is very difficult: they need to approach from afar, and by the time they reach the zone the opponent will oppose them with his steppers, needing far fewer moves to do that. And you have to overcome the extra defense provided by his Side Movers; you cannot neutralize those with your own Side Movers. Basically you can only promote steppers that are left over when all stepper material of the opponent has been traded away. So if there is an imbalance where you have steppers, and the opponent tactically equivalent sliders, and the potential promotion gain is the same, you are toast: he will promote all his sliders long before you promote your first stepper, and this will put you at such a tactical disadvantage that you will not have any steppers left by the time the opponent has not enough material left to prevent them from entering the zone.

In warfare one should never expose one's artillery to infantry attack!

Ok, HG,  thanks!

When I try to promote a Dragon King, it promotes to a Tokin instead of a Soaring Eagle. However, this can be easily fixed by making the King the last piece and changing the parameters accordingly.

Is there a new enforcing preset I'm unware of? 

No, those discussions are about the interactive diagrams.

I am nearly finished making a Game Courier preset that enforces the rules of this game and displays legal moves. However, the Lion trading rules haven't been implemented yet because they are giving me some problems. Any ideas on how to solve this?

You can find the preset here: https://www.chessvariants.com/play/pbm/play.php?game=Chu+Shogi&settings=chu

As I understand these, a lion may not capture a protected lion, and a piece may not capture a lion if one was captured on the previous move. While the second rule applies only to non-lions, it is applicable only in a situation in which a player no longer has a lion. So, that detail of the rule can be safely ignored, and it can be applied to any piece.

A player may have 2 Lions as a Kirin may be promotted to a Lion

In an engine I solve this by making a Lion that captured a Lion (from a distance, etc.)  a temporary absolute royal for one turn. Then playing Ln x protected Ln is considered exposing yourself to check. (In my Crazyhouse engine I do something similar to enforce the ban on castling through check: castling initially ends up with the Rook replaced by a second King. After move generation of the opponent (which would detect the King capture) I then replace that by the Rook it should be. After Other x Lion I make the opponent's Lion iron for one move.

All you need is the concept of 'temporary promotion', piece types that at the beginning of their own turn revert to the unpromoted form. And then have some extra types that are royal and iron.

Btw, note that the counter-strike rule on Lions does not hold when the two Lions are captured on the same square. If a Kirin captures a Lion and promotes in that same move (to Lion), it is allowed to recapture it.

Just to make perfectly clear: any piece may capture a Lion, that has captured a Lion on the previous turn. Restrictions ONLY apply after a non-Lion captures a lion. This rule has been incorrectly written in some parts of this site, which I have complained about before. And thanks for working on a new preset, Adam ^^

I will test to make sure everything else is in order

Everything should be in order apart from the restrictions against indirect trading of Lions (and the repetition rules, which i won't implement because it's way too complex). All I really did was copy the Tenjiku Shogi preset's code to this preset and modified the code to suit the needs of the Chu Shogi preset.

The preset has been posted, and everything seems to be working properly.

Would you share the link to your newest preset, Adam?

You can find it here: https://www.chessvariants.com/play/pbm/play.php?game=Chu+Shogi&settings=chu

Excellent, passed all my tests. Thanks again! I will be using this preset from now on.

Good job, Adam!...

The AI of the diagram now also has a vague notion of the Lion anti-trading rules. It isn't perfect yet, because it does not apply the rule for 'bridge capture' yet; you can just generally forbid capture of protected pieces of a certain type. It also doesn't limit it to distant captures, but I guess that only means it unjustly forbids moves that you would never want to make anyway.

@HG,

Hello,

I had just tried it and my advanced lyon defended by the DH got captured by the AI. I then tried it again. It seems to happend to player's lyon on 6th rank once the second dk pawn got moved. Maybe if you try reproducing such a position you may find the bug!...

That is not enough information to set up the position. Can you post the game that it prints below the diagram, up to the position where it happened?

And did you make sure your browser cache was refreshed, so that you are using the updated diagram script, rather than an old cached one? (BTW, counter-strike is still a problem, because the AI does not take prior moves into account. So it wouldn't know that non-Lion x Lion took place.)

The game started from regular initial position and it went like this : 1. Ng5 Cd11 2. e5 Ci11 3. j5 Nf8 4. h5 Tg10 5. Ng6 Nxg6 . I'm not sure what needs refreshing.

And by the way, talking about previous moves, is there a way they will be taken into account as I am thinking about the joker in my apothecary chess game.

Well, for me it doesn't capture the Lion, after these moves. I don't know what browser you are using, but on FireFox I can clear the cache by keeping Shift pressed during the page reload.

The diagram already supports a Betza notation for a Joker (I for Imitator). See the 'Betza sandbox' comment on Betza notation.

Wow cool thing supporting the imitator. I remember earlier versions were not able. Does the AI work also with it? This could sound silly, but random initial positions are supported?

Same with me.

1. Nf5 Cd11 2. Ne7 Ci11 3. Nxd8xe7 Ng8 4. h5 Nxe7

I had managed to clear the cache but the error still goes. I use microsoft edge.

For me it plays BT-g10 instead of Lnxe7. Your browser must be using an old cached script.

BTW, I sort of patched the counter-strike problem now, by paying more attention to what the lastest move was when invoking the AI, and making it aware of a preceding non-Lion x Lion when I set it thinking. This too isn't perfect yet. (It would miss a locust capture of the Lion by a Falcon or Eagle.) But for now it should do.

The point is that I want to replace the entire old move-entry system of the diagram, which had a move generator that directly highlighted squares, in interaction with what already had been clicked, by one based on the new move generator in the AI. The latter just generates a list of all moves, complete with all side effects. And because it can search ahead, it will be able to judge even the more complex legality conditions perfectly. The highlighting during move entry should then be based on that list, and the moves would automaticaly be in AI format, so that they can be fed back into it when it goes thinking for a reply. So it would be a bit of a waste to spend too much time patching up the old system for better interaction with the AI.

Capture bridges now also work. The anti-trading rules in Chu Shogi are so complex because they are applied to a piece capable of double capture, so that a trade could be accompanied by a sizable material gain, and they did not want to outlaw that. The same could in principle happen when several piece types of unequal value are subject to this rule. (As is the case in Tengu Dai Shogi, where Lion and Lion Dog can also not capture each other when they are protected.)

I solved it by specifying a value threshold, and when the combined gain of the capture is larger than the value of the capturer plus this threshold it can be made safely. Because the piece values are only known to the diagram, the option to specify this is tradeThreshold=N, where N is the number of the most-valuable piece that can not act as a capture bridge. So in this case I specified N=2, as the GB was defined as the second piece.

This appears to work, as can be easily tested by dragging a white Lion to i6 and a black one to g7, switch the AI on, and then drag various white pieces to h6 (and then take back 2 moves for the next try). For every piece black should then play Lnxh6xi6, except for P and GB, where it will play something else.

I thought the AI would be easy picking but it is not :)!

So, I switched to Firefox. It appears to be working better now. Still very weak AI