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The Interactive Diagram basically is a table of piece images, where the table cells are made sensitive to mouse clicks, which then can bring about the desired manipulation of the images (e.g. move them to other cells) or background colors. Such a structure would not allow drawing of image elements that span multiple cells, such as the arrows in the video.

I guess that in theory it should be possible to break up the arrows in cell-sized 'puzzle pieces' of straight parts, corner parts, arrow heads etc., in all possible orientations, and synthesize cell-spanning arrows from those pieces. The Chess pieces are actually displayed as cell background image, and have transparent background themselves, through which a background color for the cell shows (which I then use for highlighting). So technically the cells are empty, and just show a background. Images of arrow segments could be put inside them, and the non-transparent parts would then cover the piece images in the background. But this would require the images of the arrow segments to exactly fit the cell (or the browser's display algorithm would just enlarge the cells to fit the image). So it would require a different set of arrow segments for each conceivable square size. And it is a bit hard anyway to make images fit exactly in table cells; most browsers want to take some margin between the image and the cell edges, especially at the botton. So the arrows might look more like dashed lines.

Of course there still would be the problem of how a user should indicate where he wants arrows. Or other types of highlights. All in all it would not be very easy.

The current diagram already records all moves you play to make them into a game history. And on a page with a diagram you can request presence of buttons to step through a thus recorded games. For the diagrams I post here I never included such buttons, because they just serve the purpose of illustrating the piece moves and initial position. But you can see them in operation at my turn-based server, which uses the Interactive Diagram as user interface..

The old version was probably still cached. I have purged it from the cache for you.

Thanks for the reply H.G.; it is encouraging - though I still hope to one day produce more innovative CVs (IMHO).

Team-Mate Chess looks like a great CV for practicing ones' endgame technique.

Regarding your offered concept of 'meta-variants', assuming it can one day be perfectly defined, and broken down into all the already existing examples that are on CVP, it is something that appears to have slipped between the cracks for CVP. Fergus' seminal article (see CVP home page) on what makes for a CV, in the first place, IMHO breaks down various CVs, as they are differentiated from chess itself, into 6 ways of changing chess (or one might say, 6 parameters in doing so), one of which is to combine the other 5 parameters in some fashion. Then there are a number of categories CVP database organizes CVs into, such as Large Board, 3D etc.; note that I'd call 3D or higher dimensional variants a 'meta-variant', but possibly some may dispute this.

Other examples of what I'd personally recognize as meta-variants would be Ultima-style ones (Ultima was the ground-breaking CV for this), as would be variants with some type of drop (on Game Courier 'pockets' are used for storing single pieces, and also used are what I'd call 'sleeves', for storing unlimited numbers of pieces to drop) - shogi was the ground-breaking CV for this concept. Note that Chinese Chess was ground-breaking for at least its use of the then innovative cannon piece, besides having a palace limiting where a K could move to; Chinese Chess, with its use of a palace, possibly is the lead member of a meta-variant category, too.

Regarding shogi-style variants without drops, other than the 'physical' apperance of the board and pieces, I'm not sure what makes them substantially different from chesslike CVs that simply use different leapers & sliders on various board sizes (in terms of being a possible meta-variant), other than there are a lot of asymmetric and/or short-range moving pieces instead, and often a small number of special/powerful pieces that can wipe out a lot of weak enemy units if a breakthrough happens (however, other than for shogi itself, I'm pretty unfamiliar with these various CVs). A similar sort of argument might be made about shatranj-like CVs, perhaps. As an aside, perhaps an otherwise mundane  CV that introduces a novel piece (such as in many shatranj variants) might be worthy of being considered ground-breaking, especially if the piece were to prove as iconic as a Chinese Chess cannon.

From CVP home page - What is a Chess Variant?:

https://www.chessvariants.com/what.html

Something is very wrong! I try to upload an updated betza.js file to the membergraphics/MSinteractive-diagrams. It says "file uploaded successfully". When I point my browser to the MSinteractive-diagrams directory, I see the betza.js file there with today's date. All as expected.

But when I then request the content of the betza.js file, it has not changed. It still gives me the old content, not the one I just uploaded. Flushing my browser's cache, or switching to another browser makes no difference, I keep getting the content of the file that according to its date does no longer exist.

HG:

Your Interactive Diagram is undoubtedly an excellent resource to show easily the various ways of moving pieces.

Given your obvious computer skills, I wonder if you could develop a software that serve as support when analyzing chessvariants games just like many bloggers do with standard chess; features such as arrows indicating piece movements, highlighting squares of threatened pieces, soon return to the basic position after seeing one or more variants. For example, please take a look at this YouTube video. 

I mean to add said features to the Interactive Diagram. Or are they more typical of a video editor software? 

BTW, it seems my productivity is overrated in the list above: it says I invented 13 variants, but it attributes Wa and Tenjiku Shogi to me, while these are just historic Japanese games for which I made a rule-description page. (I also made such pages for Chu, Dai, Dai Dai and Maka Dai Dai Shogi, Paco Shako and Metamachy, but these were (justly) not attributed to me.) It also counts my article on FairyGen as a game invention, while this is just a description of a piece of software for generating End-Game Tables involvng fairy pieces.

It's now down to ten. I took care of the two Shogi variants, and FairyGen already wasn't listed.

You're welcome, Erik.  I'll change it for the official release.  But if you want, you can change your copy right now.  Just modify the text file in the Include sub-directory.  (Don't just rename the file, you also have to edit the first line in the file.)

Thanks, Fergus and Carlos.  I have jury duty this morning, but I will try to get the preset updated after.  But I've been sick and I'm not sure how long I will be there today so we'll see.

The definitive name of this game is 'Wildebeest Decimal Chess'. Is it possible to change the name of the corresponding preset (which I had called 'Wildebeest Chess Decimal') for the definitive name, without destroying ongoing and finished games?

I also just downloaded Chess V2.2. Great job. Thank you Greg for having included my game. No matter if you have it under its old name; but if it is a Release Candidate version, if the name could be also changed it would be more coherent with this page (even if the 2 names are nearly identical).

It is true that new variants that just slam a number of sliders, leapers, hoppers and their compounds on a rectangular board of some size are not very innovative. Even if some of the pieces they feature have never been tried before. In a sense it is like they are all the same 'meta-variant' that has a number of adjustable parameters, and by turning the knobs you can set them to values that are never tried in that combination before. As Pritchard said: "it takes only 10 sec to invent a new chess variant, and unfortunately some people do". This doesn't mean that they cannot be entertaining to play, of course. Or that they are all of the same quality. Some non-trivial work can still go in picking the initial setup, making sure all pieces can be easily developed (remove any 'awkwardness'), all pieces are protected against possible quick attacks, and such. The spectrum of piece powers is also an important factor in how attractive the game is.

Still even there you can sometimes express a novel idea. In my variant Team-Mate Chess I used a collection of not-so-special pieces that were selected to not have mating potential (against a bare King) on their own, but always must force checkmate in pairs (similar to Bishop + Knight in orthodox Chess).

BTW, it seems my productivity is overrated in the list above: it says I invented 13 variants, but it attributes Wa and Tenjiku Shogi to me, while these are just historic Japanese games for which I made a rule-description page. (I also made such pages for Chu, Dai, Dai Dai and Maka Dai Dai Shogi, Paco Shako and Metamachy, but these were (justly) not attributed to me.) It also counts my article on FairyGen as a game invention, while this is just a description of a piece of software for generating End-Game Tables involvng fairy pieces.

Thanks for the info, H.G.!

Here are some optimized versions of the B and b functions:

def B 
== #0 c1 
and flag wccanconvert 
or and == #0 g1 flag wgcanconvert
and checkleap #0 #1 1 0
and empty #1 
or and checkride #0 #1 1 1 or color #0 nor flag wcmustconvert flag wgmustconvert;

def b
== #0 c8 
and flag bccanconvert 
or and == #0 g8 flag bgcanconvert
and checkleap #0 #1 1 0
and empty #1 
or and checkride #0 #1 1 1 or not color #0 nor flag bcmustconvert flag bgmustconvert;

These do the regular Bishop move first, because that's what the Bishop will do most of the time. This can be done when neither mustconvert flag is set or when the Bishop is on the opposite color from the one it starts from. So, if a White Bishop is on a dark square (color = 1), or a Black Bishop is on a light square (color = 0), it can move as a Bishop. Testing for color #0 is quicker than testing for == color #0 1, and testing for not color #0 is faster than testing for == color #0 0, though they are a little bit more obfuscated. With regular Bishop moves out of the way, the function uses a series of breaking conditions to test whether a conversion move is possible. It first tests for conditions common to both conversion moves, testing for the less expensive one first. Also, given that these functions will frequently be used in testing whether a Bishop is attacking a King, including empty #1 as the first condition of the conversion move saves it from the trouble of checking for anything else when used for that purpose. It then tests whether it is legally converting from the g square, and if not, it uses a series of breaking conditions to test whether it is legally converting from the c square.

Greg:

I have been testing your preset and find it 100% OK, everything is working nice, but I would like to ask you a special favor: change its appearance by cloning the preset that I'm currently using whose URL is

 https://www.chessvariants.com/play/pbm/play.php?game=Symmetric+Chess&settings=default 

and its appearance is

You  know, it's something very simple: copy the code from your preset and paste it on the mine; then edit the clone with your userID and the settings name you like.

Note that in the Pre-Game box there is a line of code saying:

remind Watch Symmetric Chess games at www.youtube.com/channel/UCGEF6o8z5oW-OZlaat-Lqkg;

I use it to advertise my Youtube channel as a mean of attracting players.

The underlying reason to change the appearance is that blue pieces stand out better on an orange background than on a brown one; the same applies to the lines used to highlight the squares of origin and destination of the moves.

This is evident by comparing a whole sequence of movements.

Video with cream/brown background. 

Video with cream/orange background.  

Thank you very much for your support! 

Thanks, H.G., for your posting. I will comment something later. Rightnow I'm leaving home.

That certainly makes more sense to me. One could still wonder about the case where the first-moved Bishop does not convert, but is captured before the second moves. The situation this gives rise to is not really any different from the one where it was captured before it moved. And you would need extra game state to distinguish the two.

I guess you need extra game state anyway, because a Bishop can move and return to his starting square without converting. The other Bishop must then convert, but from the board position you cannot see which of the two is the 'other' Bishop.

Possibly the cleanest solution to everything is to implement this by piece-type changing: start both Bishops as Dragon Horses. When a Dragon Horse moves, it 'promotes' to Bishop, and as a side effect, depending on how it moves, the other Dragon Horse (which must still be on its starting square in that case if not captured), promotes, either to Wazir or to Bishop. If a Wazir moves it always promotes to Bishop. All game state is then encoded in the board position.

I still wanted to comment a bit on legality checking and game-end detection:

There is no need to assign illegal moves the same score as a legal losing game termination. You can assign it an even lower score. This reminds me of the fact that there are many Xiangqi engines that prefer losing by perpetual checking over being mated in 1. But the behavior can entirely be controlled by setting the score for the various kinds of game termination; minimax or alpha-beta doesn't require a binary game outcome. (Luckily, or the heuristic evaluation would not be any good.) If losing by illegal move gets a lower score than any form of losing by legal means, minimax should always avoid it. Unless the game rules themselves are incomplete, and allow you to manoeuvre by legal moves into positions where you have no legal moves, but which are not defined as terminal. (Most common case of this is failing to define stalemate as game end in games where the goal is King capture, under the false assumption that you will always have pseudo-legal moves.) Even in that case the illegal-move score will merely show up in the root as the most dishonorable form of losing.

It is useful to distinguish 'direct' termination conditions (detectable from the move or piece counts, such as King capture or baring) from 'indirect' ones (depending on the location of pieces and how they move). 'Check' is already a complex condition, defined in terms of pseudo-legal moves. 'Legal' (and thus illegal) are again defined in terms of check. And 'checkmate' is defined in terms of 'legal'. These definitions taken at face value often imply search, being of the form "there must not exist a move that ...". The definition of checkmate even involves a two-ply search, as it requires all pseudo-legal moves to be searched for legality, which again requires all replies to be examined for King capture.

Now it is very possible that there exist shortcuts for doing these searches, e.g. check detection through the super-piece method, or mate detection through estabishing that the checker(s) cannot (all) be captured, nothing can be interposed to block the check(s), and the King has nowhere to withdraw to. This is pretty well developed for orthodox Chess, but can get arbitrary complex in arbitrary variants. E.g. for determining whether a square is attacked when there are hoppers, bent sliders or locust capturers around (not to mention Coordinators, Immobilizers and Pincher Pawns). The super-piece method requires generation of retrograde captures, which must be handled by dedicated code, which can easily be inconsistent with the prograde move generator used in search. And for mate detection, what if there is a Lion around that can capture two checkers in one move? Or capture one, and block the other? What if there are bent sliders, that can both be blocked on a single square? What if the checkers involve a hopper, and its mount can move away, capturing or blocking another checker? How do I determine whether a locust capturer will attack me after the evasion? If I just stick to the official definition of these game concepts I only need prograde pseudo-legal-move generation, and there is not nearly as much that could go wrong.

You mentioned the 'beaten path', but you should keep in mind that this is the path used by developers of engines for orthodox Chess, and thus might not necessarily lead to where you want to be. No matter how much smartness you built into your engine for more efficient detection of the game-end conditions, it will never hurt to be prepared for game rules where these shortcuts fail, and some illegal moves escape your dedicated detection for those. So I would recommend to reserve a score for 'illegal move', (which, with checking rules, would be the negated score of capture or extinction of royal(s)), so that your engine will not crash if you inadvertantly run into a King capture. And in any node detect whether enough of the moves you thought to be legal are indeed legal, so that you would not have to declare game end after all (with an appropriate score different from the illegal-move score, like a draw or a distance-to-root-corrected losing or winning score). Which is pretty easy by starting bestScore at the illegal-move value, and see at the end if it stayed there. In cases where your dedicated game-end detection fails, your would then have a safety net in the engine. As for the GUI, you could always subject all moves to a search to make sure they are legal, and make the depth of this search a parameter of the variant, which can then be increased for variants with unusually complex game-termination rules.

So just to be absolutely sure: when moving Kf1-f3, with a black Knight on g4 attacking f2 (but pinned on the black King on g5 by a white Rook on g3), this would be illegal if f2 was empty or occupied by a white piece, but legal if it was occupied by a black piece (assuming f1 and f3 not under black attack)?

The description of the Bishop conversion rule says this:

" for one of the bishops of the player, the first move made with this bishop must be of this special type. "

I take this sentence to mean that if one of the Bishops gets captured before it moves, the other cannot start with a normal move. This doesn't seem very sensible, though, so I am not sure whether my interpretation is correct.

Just to contribute my two cents: when you would keep one flag per Bishop to indicate whether it had been moved (or per square whether the original occupant is still there), which really should be considered a standard feature automatically kept track of in any chess variant, (considering how many variants endow pieces with virgin-only moves), the game state can be ancoded with only a single other flag per player, indicating whether a conversion has already taken place. The rule for a virgin Bishop is then merely that he cannot convert when a conversion was already done, and otherwise must convert when the other Bishops is not virgin (or, since the rule is only applied on a virgin Bishop, when not both Bishops are virgin). Note that the type of move (W or B) can be easily tested from the color of the square ((x ^ y) & 1 if you have separate x and y coordinates, nr*9 & 8 for 0-63 square numbering on an 8x8 board, nr & 1 on 0-71 square numbering on 9x8).

Note that as part of an attempt to get rid of the ridiculous names of some of the CwDA pieces it was decided the Fibnif should be renamed to Lancer.

And yes, a pair of Lancers is pretty good at checkmating. An overview for various board sizes:

Given that Knight + Wazir is already won, and that blocking plays virtually no role at all in the late end-game (especially when the losing side cannot block because the squares where this could be done are attacked by the piece itself), two WazirKnights should have no problem at all. My EGT generator does not do lame leaps, but with a pair of NW the stats are:

Note that the winning percentage for N + W is not as high as commonly found in general wins. This is because a Wazir can easily be chased to doom by a King, when it happens to wake up cut off from the rest of its army. So there are a lot more positions where the strong side loses a piece despite the fact that he has the move (which otherwise are usually limited to forks in configurations where one of the pieces cannot move away while protecting the other, or attacked pieces trapped against an edge or in a corner).