Comments/Ratings for a Single Item

Although I regard Muller's list of seven desirable conditions as an excellent guideline (on most points, in my opinion) for being conducive to the possibly of creating a high-quality chess variant (which is pertinent to the title of this thread), the present question as to what defines a chess variant yields fewer conditions.

Generally, if a game has a board (2-D or 3-D) with spaces (e.g., square, 
triangular or hexagonal in 2-D), some (not necessarily all) mobile pieces
that occupy those spaces, a turn-based move order [Note:  I've never been able to successfully devise a simultaneous move game.] implying two or more players and a winning condition, it is a chess variant.  Even capturing (by various means) is not mandatory to this definition.  Also, having different piece types and abundances is not mandatory although both are strongly advisable since a lack of variety diminishes tactical depth.

So, chess variants actually include many classes of games that are not popularly classified as such.  For example:  connection games, war games, checkers variants, shogi variants, ultima variants, etc.  Furthermore, the hybrid usage of dice, cards, etc to render the overall game one of imperfect information is not prohibited.

It seems you want to erode the meaning of 'Chess variant', to become synonymous for 'board game'. I don't see what is to be gained by stretching the meaning of a term to cover something for which there already exists a perfectly good word. It gives me a definite Smurfish feeling.

We could even expand the meaning further. Why require a board, when a meadow could do? Why require turns or players? Or a winning condition? A cow is also sort of a Chess variant, right? It also moves on a 2D plane...

I think it is very good to have language where you can make a distinction between Chess (variants), Checkers (variants), Go (variants) etc.

'It seems you want to erode the meaning of 'Chess variant', to become synonymous for 'board game'.'

I don't have any 'want' whatsoever, in this case.

No.

Any one-player board game such as a puzzle or solitary connection game is definitely not a chess variant.  Therefore, chess variants, even by the most holistic, responsible definition, are merely a subset of board games.
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'I think it is very good to have language where you can make a distinction between Chess (variants), Checkers (variants), Go (variants) etc.'

I agree that distinctions in language are useful.  I also think it is equally important to recognize overwhelming similarities that are often overlooked, disregarded or trivialized.

IMHO, Muller's 7 criteria look quite useful for estimating how chess-like a game is--a continuum, rather than a binary is/isn't categorization. They would provide a conceptual framework for observations such as (to intentionally cite an extreme example) Capablanca's Chess is more chess-like than the Game of Nemeroth. Where the line is between chess variant and non-chess games cannot and indeed need not be determined exactly. The question is, is a given game chess-like enough for it to be useful to consider the game a chess variant--can a useful number of Chess concepts be helpful in playing and analyzing the game?

But drawing lines can be fun and useful if it isn't absolutized. Approached in a spirit of 'reasonable people can disagree', everyone should be free to chime in.

As a starting point for looking at some edge cases, I offer my own game Wizards' War for consideration: 
1. It has royal pieces, though capturing them is not the only method of victory.
2. It is entirely pawnless (in the Muller sense--many games are pawnless in the sense of 'this game has no piece that moves like an FIDE pawn').
So is it a chess variant or not and why? Bonus points for citing games that are clearly but not hugely more/less chess-like.

I agree that we should look for a continuum; probably the best approach is to decide upon several factors (like the Muller 7) that can be reasonably easily computed for different games.  What is perhaps lacking from the Muller7 is a measure for which aspects are most important (perhaps it is just equally weighted, but I think they should not be).  The ultimate goal (IMO) is for the measurements to come as close as possible to our collective opinion of what is 'chesslike'.  (See also Joyce's 'Chess Space', on the wikidot as well as in some comments here I believe.)

A couple of examples that might be helpful to keep in mind:
1) games using chess pieces that are not chesslike in gameplay: Joust (not very chesslike), or Knightsweeper (not chesslike at all) [both on this site]
2) Lennert's 'For the Crown' (half chess, half something else)
3) already mentioned, but Go and Checkers (and their variants; Gess perhaps?)
4) other games that are clearly not 'chesslike' but that have similarities should be noted; these might help weight the characteristics.

If 'chesslike' is not well defined enough, maybe it's useful to think in the following way.  If you wanted to tell a friend about this game, is it easier to say 'It's like chess, but...' or just to start from another game (or from nothing at all)?  Of course, some games will be equally easy to start from chess or to start from some other game (e.g., For the Crown seems easier to describe as 'like Dominion, but with chess', but maybe for some people, 'like chess, but with deck building' is better).

Oh, and maybe it's good to distinguish between a theoretical classification and guidelines for this site.  I tend to think this site should be very inclusive, but am happy to draw the boundaries tighter in theoretical talks.

Is this chess?

    
http://www.chessvariants.org/index/msdisplay.php?itemid=MSchesimals:auto

Here's my take after a little thought. The point assignments probably need work.

A game which is a form of chess, is one which includes all of the following properties:

1. A game of movement and capture, rarely of placement (2 points)
2. Bilateral symmetry and equality of material (1 point)
3. Functionally differentiated pieces (2 points)
4. Capture by replacement (1 point)
5. Win by capturing a definitive singleton (royal piece) (3 points)
6. A Turn-based game (1 point)
7. A Two-player game (1 point)
8. A game of Complete information (1 point)
9. Played by moving pieces between discrete positions (2 points)
10. The players can move one piece per turn (1 point)
11. One piece type is more abundant than the others, quite weak, moves uni-directionally and can promote (1 point)


[1-5 (but not the point system) taken from: Parlett, D. S. (1999). The Oxford history of board games. Oxford: Oxford University Press. p. 277.]

[6-11 (but not the point system) taken from H. G. Muller's post on chessvariants.org commenting system.]

Suggested terms:

Chess-game: 16 points (all properties)
Chess-like game: 10-15 points (many properties)
Chess-related game: 4-9 points (some properties)

Note that many chess variants are (according to this scheme) chess-like or chess-related games.

Examples:

Go                = 0 + 1 + 0 + 0 + 0 + 1 + 1 + 1 +0/1+ 1 + 0 = 5/6
Checkers          = 2 + 1 + 0 + 0 + 0 + 1 + 1 + 1 + 2 + 1 + 0 = 9
Losing Chess      = 2 + 1 + 2 + 1 + 0 + 1 + 1 + 1 + 2 + 1 + 1 = 13
Extinction Chess  = 2 + 1 + 2 + 1 +0/1+ 1 + 1 + 1 + 2 + 1 + 1 = 13/14
Ultima            = 2 + 1 + 2 + 0 + 3 + 1 + 1 + 1 + 2 + 1 + 0 = 14
Progressive chess = 2 + 1 + 2 + 1 + 3 + 1 + 1 + 1 + 2 + 0 + 1 = 15
Grand chess       = 2 + 1 + 2 + 1 + 3 + 1 + 1 + 1 + 2 + 1 + 1 = 16

David, I also find the 'point-count' classification interesting and possibly fruitful.  One interested in games in general might establish 'point-count' characteristics for other types of games, and then for those games that are ambiguous, one could perhaps, for instance, compare the various 'point-count' analyses of a difficult case like Nemoroth to decide whether it is more a Chess variant or a Fox-and-geese variant.
One of the characteristics could be, as trivial as it sounds, does any game in question take advantage of the physical nature of a chess set to define or clarify aspects of its own rules?

David Howe made a list of some features of a chess variant game. I am going to list a few more (but without assigning points to them):

12. Game does not involve physical dexterity, drinking, etc, so it could be put into a computer; but no computer is required to play game in general.
13. Real time taken does not affect the rules of the game (except the tournament rules, which might give you time limits, and stuff like that).
14. Board is finite and the geometry/topology of the board won't change during the game.
15. The game is played using standard chess pieces and chess board.
16. There is no decision other than the movement of the pieces.
17. Pieces moves like chess pieces can move.
18. You will normally have a choice of which piece to move and which way to move it (within the restrictions of the rules).
19. Game has well-defined ending condition.
20. You win, or lose, or draw; it is not ambiguous and you do not win by a number of points which can vary.
21. The different function of different pieces is mostly only their difference of movement.
22. Pieces belong to a player.

Some games might partially or almost have a property listed but not entirely, or have slight variations on the properties listed (for example, more than one royal piece, or some pieces captures by displacement and others don't, or special circumstances in which you can move more than one piece, etc).

I think Nemoroth is a chess variant: Humans is like the pawns (weakly, more of them at the start, cannot retreat, and promotes); uses equal sides; different pieces of different function; etc. But in chess the pieces just move differently while in Nemoroth their other functions also vary a lot. There are many other differences too rather than make them like other chess variant games.

P.S.: You still did not fix the bold footer (there is an extra B tag which should be removed)

Good game design is ultimately a matter of generating appropriate reactions in players.  Analyzing how people feel about games they've played (and why) can suggest new ways for a designer to elicit (or avoid) particular reactions.  Making lists of things that contribute to an overall 'chess-like' impression seems like a pretty reasonable thing for chess variant designers to spend time doing.

Assigning actual point values is probably reaching beyond the available data, though.  Verify your models carefully before you trust them.

> 22. Pieces belong to a player.

Good point. It did not occur to me to mention this, but for me it carries as least as much weight as any other of the characteristics I mentioned.

OTOH, I would not put any weight on things like 'pieces should move like Chess pieces' or 'Can be played with Chess board and pieces'. This seems to single out a specific variant (namely Mad Queen) as overwhelmingly more important than the others. While IMO it is just one of the many Chess variant, and not even the most popular one on the planet.

Furthermore, a point system should take into account that the characteristics are not just boolean all-or-nothing things. For my perception of Chess-likeness it definitely matters if the rules are mildly violated (e.p. capture and castling in Mad Queen), or badly violated (e.g. almost no piece captures by replacement, as in Ultima). So the question is more if the typical behavior satisfies the requirements, rather than that no exception at all is tolerated.

The concept of 'recognized variant', in the sense of very widely played, should probably play some rule too. For instance, if a game is on the edge w.r.t. the number and severity of how it violates the defining characteristics, it should never be pushed over the edge based on whether it also allows e.p. capture or not. This particular transgression of the replacement-capture requirement should be designated 'acceptable' because it is so common (which no doubt can be traced back to the popularity of the recognized variant that incorporates it.)

There also seems to be need to weight the opposite: likeness to very popular games recognized to be not Chess variants. If Checkers would be recognized as an independent game, (which I think the vast majority of people would agree on), I would be inclined to reject games that are more like Checkers than like Chess, even if in an objective measure they are closer to Chess than some other variants which do not happen to be close to any other recognized game either.

[23] All squares are essentially equal, there is no terrain to consider.

This criterion draws a line to war simulation games, where land, water and cities play an important role.  

Xiang Qi mildly violates this one.

I suspect there's several concepts concealed in J�rg's [23].

One could be that squares differ only by their relative positions; for example, there's no square where you become immune to capture, or that can only be crossed by certain piece types, or whose occupation immediately wins the game.  Though this would be violated not only by the river and palace in Xiangqi, but also by piece promotion in FIDE and Shogi, which perhaps calls into question the validity of that criterion.

On the other hand, you can still make many kinds of 'terrain' just by altering the connections between squares; for example, you could have a 'wall' between squares (causing them to not be considered adjacent), or a 'portal' (that causes two otherwise distant squares to be considered adjacent), or a 'rotated' square (that turns forward movement into backwards movement, or orthogonal into diagonal, for example), all of which can be completely described purely as changes to the connections between squares.

So perhaps you want a rule something like 'the squares comprise a regular tesselation of the playing field'.

And possibly another requirement specifying the overall shape of the playing field (e.g. rectangular).

Side-Topics:
 - Chess variants on boards with semi-regular tesselations
 - Chess variants played on an arbitrary graph

Back to the terrain question: a promotion zone does not constitute terrain for me, also the forward direction of pawns is not dictated by terrain.

Holes in the the board are somewhat strange to Chess and may constitute terrain. Barriers of all kind are certainly terrain.

Possible terrain effect are: Difficult terrain (mountains, swamps) slowing units (pieces) down or forbidding some kind of pieces (two heavy to move there ...) on that terrain, land/water distinction (land units need boats or bridges to cross the water, water units cannot move on land (but maybe shoot units down on land), air planes can operate both on land and water, but need to land after some time and need airports or carriers for this purpose), cities (providing supplies fo any kind, generating new units, allowing of repair of damaged units).

This leads to another chess criterion

[24] A chess piece is either fully functional or captured, there is no such thing like 'damage' or 'health' with consequences to the piece (slower motion, need of repair, easier capturability). Of course, a bad position (e.g. pinned) does not count as damage. In FIDE chess the only (very mild) violation of the no damage rule is the loss of castling rights.

Here's my interpretation of A. Blacks criterion 17:

17. Pieces moves like chess pieces can move.

(a) Pieces move like leapers (true leapers or 'lame' leapers), riders, chinese or korean cannons, or combinations of those.

(b) Pieces have highly symmetric movement patterns (full 90 degrees rotational and reflectional symmetry for all non-pawn pieces, reflectional symmetry with different forward and backwards movement [like in the Shogi gold and silver generals] counts as a mild violation of this)

(c) Pieces move and capture the same way or their move and capture are at least 'similar' in some sense (I consider the pawn movement and capture similar because of forwardness and shortrangeness, also the pieces of separate realm chess or chinese cannons are similar in movement and capture. Frank Maus' knibis and bishight aren't). 

This allow much more pieces than just the traditional FIDEs ...

[25] There is Zugzwang: players with legal moves are obliged to move even if every legal move leads to defeat.

This is one of the most outstanding features of chess and its variants. Compare it to go, where no player is ever forced to deteriorate their position, they may just pass instead.

On "Don't overcomplicate your game", I'm wondering about even the popular variant Rococo perhaps not quite satisfying this criteria. Just looking at how long the entire description of the various pieces' powers is for the game, it does seem there are many rules (plus arguably unfamiliar piece types) - and perhaps because I am not always inclined to learn a hard game to play, I haven't hurried to do so in this case either. Note that people can understand the basic flow of a physical sports game without knowing every rule, but it seems tougher to do so for even a game of chess, which seems less complex rule-wise than Rococo does - yet I suppose the latter is an enjoyable game once one fully learns it. Lately it does not seem much played on Game Courier, perhaps because there are a lot more relatively new people to CVP (like myself) playing nowadays.

Rococo

On an unrelated matter, other than reviews or comments, it's a bit hard to tell if one has invented a chess variant that will ever be played or liked much at some point. So far I've submitted 17 variants, and 11 of these have Game Courier presets. Of the latter, only two games of mine have been played more than once (or in the case of many, if at all), so far. At one point I gave myself the objective of inventing at least one game per certain common types of board terrain that could be played on Game Courier, if there ever were a preset made for each game. Later I thought more about how to design a game that might have a strong chance of being popular, and Butterfly Chess had some success, though not as much as when I lucked out as a beginner to some extent with Sac Chess. One problem may be that that most of my presets are not rules enforcing, which may give a game a better chance of becoming popular; another thing that might make a game popular on Game Courier might be simply being an inventor and player familiar to many Game Courier players, ideally with a history of inventing a number of successful variants. Anyway, my modest 'success' with 2 out of 11 presets thus far is a success rate inventors in other fields of endeavour might not feel too bad about, especially if just starting out.

Butterfly Chess

Sac Chess

Contrary to Kevin, Rococo is the most played not the least played lately in recent finished Games (rhymes with Trump and crowd size). The article is too lengthy for having two inventors. My top CV of all 3000 in sixty words, enough to start playing immediately, the whole simplified rules:

All pieces have to move the same  like Queen but land on border square only if/in capturing. Pieces capture along Q lines like in  Abbott's Ultima and in Parton's classic CVs. See Advancer, Withdrawer, Chameleon, Swapper, Immobilizer capturing in video. King is f.i.d.e. and the only one moving and capturing the same. Cannon Pawn is specialized one- or two-stepper, also having unique capture.

Regarding Rococo, it is currently the 14th most played game on Game Courier out of a total of 1141 games. In the past 90 days, it has been played five times, though every single one of those games was played between George Duke and someone literally called "?? ??". So that doesn't say much for its current popularity. Personally, I don't play it myself, because I'm not into Ultima style games. So, I never wrote up these design goals and principles with Rococo in mind as an example, and perhaps it is difficult for these kinds of games to not be overcomplicated, though I think David and Peter did try to make it less overcomplicated than Ultima.

Regarding games without rule enforcement, I usually avoid playing them myself, and I don't give them the same promotion as I give to some games with rule enforcement. So I do think it is a good idea to provide rule enforcement if you want people to play your games on Game Courier.