Comments/Ratings for a Single Item

OK, thank you for clearing this up. I will make the article conform to the Zillions implementation.

Perhaps you could try the following as well? (I don't have Zillions):

Is the not-passing-through-check rule also enforced when the square jumped over is occupied? And does it depend on the player to which the occupying piece belongs? Logically, if the King tries to move f1-d1, and e1 is attacked (by a Knight, say), it should be forbidden when there is a friendly piece on e1, but allowed if there is an enemy, as the Knight cannot capture the King on e1 when there also is a piece of his own on e1. (At least, I think so; it is not very logical in the first place that the King could be on a square already occupied by another piece, to be checked there...)

The code for the King's skip move looks like this:

  (define skip
( 
(verify never-moved?) 
(verify not-attacked?)
	   $1 
	(verify not-attacked?)
	   $2
		(verify empty?)
	        (set-attribute never-moved? false)
	   ;     (set-attribute never-skipped? false)
		 add
	 ))

The only condition on the first step of this move is that the space is not attacked. A space is considered attacked in Zillions-of-Games only when an enemy piece could legally move there.

Well, I don't understand Zillions coding. But do you mean 'legally' as 'also not leaving the player in check'? I.e. would player A be allowed to move his virgin King from f1 to d1 if e1 was attacked by a Rook of player B that was pinned on the King of player B?

For orthodox Chess being in check is defined in terms of pseudo-legal moves, and 'not passing through check' would also forbid castling when a pinned piece attacks the square through which the King passes, and thus does not have a legal move to that square.

Capturing your own pieces is not even pseudo-legal, however, so I guess it is would never be a problem to jump over an enemy piece.

Here's how the function works. It starts with the piece on the space it was already on before moving. It then verifies two things, that the piece hasn't moved, and that it is not attacked. The first checks an attribute of the piece, and the second checks whether an enemy piece could reach the space using its powers of movement. If these are both true, it continues to process the move. The $1 is a variable standing in for the first argument passed to the function. This will be a direction, and it will move in that direction to a new space. It then verifies that this space is not attacked. If this is true, it then proceeds in the direction provided by the second argument, $2. The one thing it verifies here is that the space is empty. If it is, it continues with the rest of the function. The next line sets the piece attribute "never-moved?" to false, which will stop the piece from making a second move of this type. The line after this is commented out. It would have set an attribute that appears to be redundant and unused. With the last line, the add command makes this an official legal move, understood in terms of the piece's powers of movement, but not in terms of whether the move would create an illegal position.

Consider the game of Chess. A King cannot legally move to a space the other King could otherwise move to, because then it would be moving into check. This implies that each King can attack a space it cannot actually legally move to. And this is what attacked means in Zillions-of-Games. It identifies a space that the King would be in check on if it moved there.

Ah, but this is new information. You can also not make the jump when in check. I did not get that from the description on Jean-Louis' website.

Btw, it seems that this in-check business has been a seriously disputed issue at one time in the history of orthodox Chess, whether you could be in check by a pinned piece, or whether you could step your King next to an enemy King when you were protected (so that the opponent King could not legally move to the square your King was on to capture the latter). In Tai Shogi there is a similar issue, because there is a rule that says an Emperor (which is a universal leaper) cannot capture a protected piece, and it is not clear whether a piece is protected by the opponent Emperor (as he is also subject to this rule, and might thus not be able to recapture your Emperor if you had a second attacker to the square).

But I understand that this 'attacked' test in Zillions would never say that a piece is attacked by a piece of the same player.

There's a problem here. The Pawns and Princes promote only to Queen, and never to Lion or Eagle.

Oh, it seems I broke something when making it possible to have multiple diagrams on one page: all collapsable legends now get different HTML IDs, so the test whether the legend table is open or closed, which decides whether you automatically get the default piece, now looks for a legend with the wrong name, and as a result considers it closed.

[Edit] OK, I fixed the JavaScript, and now you will have again promotion choice. (In the legend table, when it is open. When it is collapsed, you get the default piece, which is Queen here.) Don't forget to hold Shift down when you reload the Metamachy article, to also force loading the new .js file instead of using the cached one.

I made a GC preset for Metamachy here.

I have made good progress toward making a rule-enforcing preset for Metamachy. The last thing to do is to enable Black to place pieces before White moves. Game Courier is not currently set up to allow anyone to do anything before the first player moves. One way to handle this would be to give the first move to Black, but this would involve inverting the board, switching the sections coding for each side, and listing White as the second player in the movelist. I would rather avoid all that, but that means working out a way to allow the second player a pre-game move.

Well, I guess black logically is the first player in Metamachy. Don't you have the same problem in Shogi?

Ideally, I want to treat Metamachy as a game in which White has the first move of the first turn but Black has a special setup move before White moves. The trouble is that the more complicated Game Courier has gotten, the more difficult it has become to change how it behaves. I have some ideas for what to do, but I also worry about breaking things to get it done. It also takes a lot of inspection of the code to figure out how it works and what can be changed. Some of my ideas might also be useful for supporting multi-player games, but that's another thing I have not added yet because of the difficulty in doing so.

Hello friends,

Two things. I would like to know what was not clear in my description of metamachy? I could make corrections.

Second, it is a bit severe against me as the inventor to write about the Prince "Despite what its name suggests, it has no royal properties". It moves like a King, I think this is a strong royal property. It can be checked, and this is logical, the capture of the Prince should not be the end. A Prince is not a King. Its name is well chosen or I miss something.

Best regards

The term "royal" in this context specifically means the "capture/mate me to win" property. The term "prince" has been used both for pieces with the King-move but no such property (Tempête sur l'Échiquier comes to mind) and for pieces that serve as a backup royal (Chu Shogi, Tamerlane). Prince is a reasonable term for either, but the clarification is also reasonable.

Not clear from your description at http://history.chess.free.fr/metamachy.htm was:

• Whether stalemate is a win, draw or loss.
• What the "overpassed squares" are in case of the initial King move to the second ring. In particular whether moving like a Knight (from f1 to g3, say) passes over f2, g2, neither, either or both. And what it means for those squares to be "under attack" when they are occupied. (For D or A move it can be assumed that these are the W and F squares in the same direction, respectively.)
• Whether the King can capture with its initial jumping moves.
• Whether a Prince can capture en passant, in addition to being e.p.-capturable. Especially since, in the description of the Pawn, you present its ability to capture e.p. as a "consequence" of its ability to capture diagonally, rather than as an additional rule that could very well have been different. Since the Prince can also capture diagonally, does this have the same (but this time unmentioned) 'consequence'? And is this then a consequence just of being able to capture, (so that the Prince can also e.p.-capture orthogonally), or does the direction matter (and how about backward diagonal then)?

Note that my remark on the non-royal nature of the Prince is not meant as criticism on you piece naming, but just as a warning to the reader that the Metamachy type of Prince is not like the Shogi Prince (which also moves like King) in that it has to be captured / mated too in order to win the game and cannot expose itself to pseudo-legal attack. I would have said the same for Queen where it not that the Queen is an orthodox Chess piece that can move into check, and would automatically be assumed the same in other variants. Note that in your Metamachy description you use 'royal' in exactly the same meaning as I use it here, when you describe the Prince as "a non-royal King".

Thank you for all these explanations and feedbacks. I will correct soon the description on my own page. 

• The end-o-game rules, checkmate, stalemate, etc. are identical to standard chess
• King's jump: you guessed well. At his first move, the King may jump to a free square at 2 squares' distance. It does not matter if the square jumped over is occupied or not; however, the jump os forbidden if that intermediate square is threatened by an enemy piece. When jumping like a Knight, at least one of the two intermediate squares must be free of threat. The King's jump is not permitted if the King is in check.
• The King cannot capture with its initial jumping moves (it may jump to a free square only)
• En passant: any time a Pawn or a Prince takes a double step and passes through the capture square of an opposing Pawn, that Pawn may capture the Pawn or the Prince as if it had only moved one square. This en passant capture must be made in the immediate move following the double step. Only a Pawn may capture en passant; the Prince does not have this option.

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)?

For what it's worth, here's my tentative estimates for the piece values of this (12x12) variant, at least in the endgame phase:

Pa=1.6; El= 1.76; Cam=2; N=2.6; Can=2.75; Pr=3.58; B=3.75; R=5.5; Li=8.12 Ea=9.23; Q=10.25 and K's fighting value=1.77.

In my game here, I want to capture En Passant.  It does not show as a legal move, although if I tell it to make the move anyway, it does work.

That's now fixed. The function was testing whether a rankname equalled a filename, which would always return false. It was supposed to compare the ranknames of two coordinates.

Confirmed.  Thanks!

Pretty sure I prefer the Eagle over a Queen. So much versatility.

Before finalizing my own tentative estimate for the value of the Eagle (quite a bit less than a queen), I read Ralph Betza's article on Bent Riders, in the Piece Articles section of this website. If I understood his writings right, I'd already arrived at a similar value to what his would be for the Gryphon (what is called the Eagle in this game), even though I used a sketchier form of calculation. However, Betza worked out his theories for piece values before people began to try to estimate fairy piece values with the aid of computers.

P.S.: In the Piece Articles section, too, the Article 'Who is Who on Eight by Eight' puts ZoG's value for a Gryphon only about a chess pawn's worth less than a queen, so quite a difference in value, although those are old ZoG values that need to be taken with a grain of salt in many cases.

Where the Queen provides distributed pressure, the Gryphon provides concentrated pressure. Against reasonable play, where you expect your opponent to try to make his pieces work together (reasonable to assume pieces are relatively close together), I assert that the Gryphon is a better piece for pressuring the opponent overall. Even when kicked away, it can often still maintain distant defense. And the forking potential is massive.

I was never one to subscribe to a calculatory method of evaluating piece values, rather in favor of practical analysis through actual play. 

Even if I were to concede that a Gryphon is about a pawn less in worth than a Queen on an 8×8 board (which I do not), it makes sense that the Gryphon's initial diagonal move would mitigate its strength more so on the smaller board than on the 12×12 board of Metamachy, so for this game its value should be at least comparable if not superior.

It seems upon re-checking, I made an error in my calculations for the Eagle's value, then reinforced that by reading Betza's article the wrong way. For now I'll go back and use a value based on the old ZoG article's exact ratio that's found between a gryphon (Eagle, here) and a queen, if only for the sake of providing a quick and dirty numerical estimate, even though it may prove to be too low later on (with much experience). The value of bent riders is something I hadn't tried to calculate on my own before.

P.S.: If I am now reading the Betza article right, he values a gryphon (i.e. Eagle) as worth 88% of a queen, which is almost exactly the value that the old ZoG article implies it has.