I have just added the GC code for the above game between the inventor and
Ben Good. There seems to be a contradiction between this game and the zrf
and GC Preset. Do the Queens face each other?
(I have also changed the illegal 18... Le5 to 18... Le6; there may be
other errors in the transcription, since some moves look a bit strange.)

I agree Centennial and Millennial Chess are two of best large-board CVs. 
Pieces are clear, not too many types, and interact well.

This is a very good 10x10 chess variant, ranking perhaps a little below Shako. I must disagree with some of the piece values given, especially in the endgame. I consider a Ferz to be worth at least a quarter of a Rook on 10x10 boards, so the Steward (adding noncapturing Wazir moves) should be worth at least two-fifths of a Rook.

Queen=9.1, Rook=5.0, Murray Lion=??, Bishop=3.1, Knight=2.7, Camel=2.5, Steward=??, Pawn=0.9 are consistent with the endgame values I have been using for years. While 'three-leapers' like the Camel appear to perform very well on 10x10 boards, I cannot value this awkward colorbound piece higher than half a Rook. In any variant where they can promote to Queens, five connected Pawns stand a good chance of defeating a lone Rook. See Opulent Lemurian Shatranj for a 10x10 chess variant, which also has a Commoner worth at least 3.1 points on this scale. The Murray Lion is a strange piece which, I believe, shares the Commoner's ability to checkmate a lone King. I value it somewhere between a Bishop and a Rook.

Centennial Chess

This is another chess variant that is quite popular on this site. In contains the innovative feature of an asymmetric piece (the Rotating Spearman) that can change its orientation at the end of its turn, deciding how it will be able to move the next time. It also contains several other unorthodox pieces, and thus makes a grateful subject for presentation as interactive diagram:

Spearman orientation

The main challenge here of course was to implement the re-orietation of the Spearmen. This required some extra scripting, through one of the standard 'hooks' of the basic diagram script, providing the (optional) function 'WeirdPromotion'. Because the re-orietation of the Spearmen is treated as promotion of one piece type to another, where Middle,Left and Right Spearman are defined as three different piece types.

To make this work satisfactorily, the basic JavaScript powering the diagram had to be enhanced a bit, because it was necessary to make WeirdPromotion invoke the promotion procedure normally used in wester Chess variants, where you can select the promotion piece from the table by clicking there. Before this WeirdPromotion wasonly used in Shogi variants, where there is no choice other than to promote or not. The was solved by making the choice of the (normally non-existent) piece number 1022 indicated by WeirdPromotion be interpreted as a wildcard, allowing the user to select the actual piece from the table. Since WeirdPromotion (when supplied) is called after every move, it just has to test whether the moved piece is one of the Spearmen orientations, and if it is, wait for the user to select the new orientation.

To make this selection of new Spearman orientation easier, the table of pieces is printed next to the board permanently, rather than in the default way as an initially collapsed table under the board. Placement of the table anywhere in the page can be achieved by defining a HTML element <table id="pieceTable"></table> in the desired location.

Castling

Castling was also a bit problematic in this variant, because the King moves a different number of squares on the King side and Queen side. While the setup is such that what is left for white is right for black. So using Betza l and r modifiers would need a different description for white and black King. A new feature was added to the basic diagram script to handle this situation in a more convenient way: a new parameter 'castleFlip', when set to '1' in the diagram definition, will cause the meaning of left and right to be reversed when interpreting the XBetza description of castling for a black piece.

This looks like a really interesting game. The movement rules certainly speed up play on a large board.

From the Introduction to this page: "...Such 10x10 games, often called decimal chess, have been the holy grail of game designers for ages. Many scholars felt that the move to a 10x10 board would be the next logical step in the chess's continuing evolution..."

I've been recently thinking about this matter (whether the 'next chess' ought to be played using a 10x10 square board), not for the first time. My initial thought was that 10x10 is the biggest square board one could nicely fit on a coffeetable, with squares and pieces of reasonable size (most people I thought would prefer a square board over a rectangular one for aesthetic reasons). Such a board could also accomodate a much larger number of pieces, say up to 60 (lately I've wondered if that's too many pieces to store conveniently in a box or bag, also with the slight extra time used to put away or take out every time too - plus more noise made doing so, at a club or event, all arguably a slight irritation). I have also read that at least some chess grandmasters think 10x10 may be too overwhelming, say for calculating purposes in a game, however.

Also, unless both sides armies are placed only on the first two ranks, which restricts the maximum size of an army to 20 units, the pleasing possibilities of smothered and back-rank mates would often be lost for a variant, I'd assume (at least if FIDE pawns and pieces are included in the setup, and in a pleasing way). I also thought about 9x9 or 11x11 boards, but they are awkward if two bishops (or another colour-bound piece pair) are desired to be included - other than that, shogi and possibly wa shogi (maybe just with the use of drops) are nice chess variants that just might smoothly take over from chess as the next chess, if only western eyes might like the odd physical pieces (and maybe their movements) more, perhaps.

All that led me to revisit rectangular boards as perhaps an ideal next step for finding a variant surpassing the domination of (western) chess. 12x8 is already a little too wide (see what I alluded to in my second paragraph), and it makes castling take much longer, unless a new form of castling is introduced, which may not prove to be popular (I made such an attempt with my own 12x8 Wide Chess variant). Variants that are 11x8 are awkward, in that bishops to be symmetrically placed in a pleasing way for most people need to be on the same coloured squares in the setup, with some sort of bishop's adjustment/conversion rule to allow one bishop to go to the other colour for the duration of a game, a rule which so far hasn't seemed to be extremely popular in Game Courier play for any number of board sizes or shapes. Variants that are 9x8 would only allow for one more piece to be added to the first rank of an army, if chess tradition is respected at least in so far as pawns and a 50% pieces to empty squares ratio is used.

That left me with 10x8 boards (assuming hexagonal or circular boards, for example, could never prove popular enough due to the oddities caused by their geometry, alone).. If I respect having pawns and a 50% pieces to empty cells ratio for a setup (maybe awkward for 10x10 variants), that allows for (just) two more pieces to be added per side. I'm not sure that's enough that such a variant's opening theory would not be exhausted for a very long time, as I imagine would be desired by many, if a random setup like chess960 were not used (chess960 would be extremely excellent for this purpose, except a lot of its setups are a bit awkward or advantegous to White compared to chess, and that might be true of random 10x8 variant setups too, and forget about setting up the pieces on your coffeetable, in a store or in a movie, with no fixed setup).

Having re-thought about all this, I'm once again thinking 10x10 square boards are the most promising way of the future for chess lovers, as John Brown stated above, with little things like possibly lost smothered and bank-rank mates being damned. Does anyone have any thoughts on any of this?

For short my take is the bigger the better. But the bigger means also more difficult to design:)!

An advantage of 10x10 boards is that they are easy to obtain in all qualities from cheap and ugly to beautiful and only moderately priced, because of International Draughts. I have two of thos myself, not because I play Draughts, but because they usually are on the flip side of an 8x8 Chess board.

On the new Chess Variant forum there is a contest for designing 10x10 variants; I think the submission date just closed today. I submitted a variant 'Decimaka', with 26 pieces per player, to stay close to a 25% board fill. Pawns shifted up to 3rd rank, to have the usual 4-rank 'battle theatre', and no need for new Pawn moves. The back rank only contains 6 pieces, amongst which King and Rooks, and two pieces that can (amongst others) jump 3 diagonally forward, so that castling can be quick.

The inspiration for the variant, which makes it (quite) different from 'ordinary', was Maka Dai Dai Shogi. This means that most pieces promote, and Pawns promote only weakly, but promotion is on capture, rather than on reaching a zone.

This morning I took a look at the Historic Chess Variants category on CVP, and looking for tested variants using a large number of units per army (not counting shogi variants, or those for more than 2 players), I found 2 such variants (Tamerlane and Duke of Rutland's), neither 10x10, that use 28 pieces per side, albeit without exceeding the arguably desirable 50% ratio of pieces to empty cells. I don't know if either of these games were ever played in clubs or big tournaments at any time, though. 12x8 Courier Chess (and also Courier-Spiel to a lesser extent) lasted in vogue in Germany quite a while, and each used a 50% ratio of pieces to empty cells, with a total of 24 pieces per side. I'd guess these variants didn't largely fall away because they used a large number of pieces and pawns, but rather for other reasons. Maybe the board size and shape being awkward wasn't a big cause, either - presumably quite a few boards of this size were made in Germany (where I noticed elsewhere that 10x8 boards for Janus Chess have been made in modern times, too).

In our chess club in Ottawa there is one unusual (largely red and white) paper board people occasionally use that is wide, because the national & provincial flags are printed in the margins to its 8x8 board. A table in our club is suitable for 6 players normally, but just 4 perhaps when that board is being used.

In my elementary school days there used to be very cheap school sets that were used that featured smaller pieces and boards, and I suppose people could get used to such pieces if they were of better quality, with use of e.g. 12x8 boards that had to have physically slightly smaller squares than we're used to for quality 8x8 boards. A Scrabble game board is 15x15 after all, and clubs with adults have no problem using such for serious events. So, perhaps there is little problem with variants larger than 10x10 in this way, if such boards ever get mass produced due to a suddenly popular variant or two of that board size (as an aside, in the odd search result I've seen some people still ask where they can find 10x10 boards, or even 10x8 ones along with a nice Capablanca Chess set). I may take a fresh look at creating 12x8 variants, even if there's little chance one will ever set the world on fire. I suspect the demise of chess won't be for 100+ years anyway, more or less. :)

Back in [2018-03-04] Kevin Pacey mentioned "the pleasing possibilities of smothered ... mates".  My 12x12 variant Rose Chess XII has 96 empty squares, with ten Pawns each on the 4th and 9th ranks.  But Black can deliver a smothering mate with a circular Nightrider on the second move of the game.  A position so amusing that it earned a diagram at the top of the rules page.