Comments by H. G. Muller

Not sure I have seen that poll.

But I would say that a mimic moves / promotes / does whatever as the rules of the variant it participates in says it does. It is not a standard piece. Usually mimicking is about moving, and things like promotions or royalty are not part of the move. Of course you could define a piece that mimics the promotion of the last-moved piece too. Or even only that, always keeping its own move, but allowed to promote on it (no matter where it goes) when the opponent promoted. Or even promote in its own prescribed way when the opponent promoted. The possibilities are endless. Of course promotion of a mimic would in general make it a non-mimic. (Unless a game has various types of mimics in it.)

A generalization of a mimic is a piece whose move and/or other properties depends in some way on the previous move of the opponent.

EGT on plain 8x8 boards can be generated with FairyGen, and I can confirm that Dragon Horse beats Knight there. As well as Bishop, Nightrider, Woody Rook (WD), Modern Elephant (FA), Phoenix (WA). It cannot beat a Commoner, though. But that is no surprise; even a Queen cannot beat a Commoner, when the latter is connected with its King. (Because the enemy King cannot approach it.)

Mate with Knight + Alibaba is an interesting case. The Alibaba is a 'potent' piece because of its D move, so if you can drive the bare King to a corner the Alibaba can reach, checkmating is easy. But of course the Alibaba can only acces 1/4 of the board, and on 8x8 there always is a single corner it can reach. (The Alibaba is also 'forking' in those corners, and together with the 'semi-potent' Knight it can also force an edge mate there, but that doesn't provide extra possibilities.) Apparently it is too difficult for Knight + Alibaba to drive the bare King to the deadly corner from any of the other corners, so the end-game is a general draw, with only 1% of the positions with black on move a forced loss. (Presumably because the bare King is already trapped in the deadly corner there.)

On 9x9 this goes up to 24%. In this case all corners are equivalent, and 1 of the 4 Alibaba placements (31% to be exact) allows forcing of checkmate in all 4 corners. When stalemating is a win 77% of the positions with black on move is lost. (And 99.3% of the positions with white on move is won.)

Also make sure that graphicsDir contains a valid URL to the piece images. If you want to use those on CVP from home, you should add the website, otherwise it will search the images on your own machine. (Which would be OK if you copied those there.)

It should not come as a surprise that elementary end-games can be completely different in Alice Chess. The pieces only superficially mimic the orthodox pieces, but in fact are completely different beasts: they are al locusts, which capture in passing, and should end on an empty square. So one cannot assume end-games like KBBK, KBNK or KNNK get the same result as in orthodox Chess. I am not sure if it has ever been studied whether these end-games are general wins.

KRK (and hence KQK) seems winnable, because a King is rather vulnerable in Alice Chess: it is not only forbidden to end on a square that is attacked, but also to pass through one. So Alice pieces are pretty good at confining a King; it does not really matter which board they are on. That means a Rook confines a King just like it would in orthodox Chess, and putting the Rook on the same rank or file as the bare King while you have opposition drives the bare King back in the same way, even if it would not actually check because it is on the other board. So the technique is pretty much the same.

Only for delivering the mate you have to be careful that the Rook actually checks, or it would be stalemate. Which is not entirely trivial, because pieces cannot triangulate in Alice Chess. But when a bare King gets confined to a1-b1 with the other King on b3, a Rook on the c-file can either go to c1 in one or two moves to get it on the right board, and to make sure the bare King is on a1 in both cases an extra King move b3-a3 can be played

The Troitsky study exploit the fact that two Knights can easily force stalemate, so that KNNK would be won if stalemate did not cause an instant draw (e.g. because it is an instant win, or forces the opponent to pass a turn). The extra Pawn provides moves that spoil the stalemate to achieve a similar effect, giving one of the Knights time to manoeuvre to the mating square while the black King stands trapped in a corner. But there still is a deadline in achieving this, as at some point the Pawn will promote, and the moves of the resulting Queen will no longer be irrelevant.

In the shown position the Knight is just in time to deliver mate before the Queen can be used, but in Alice Chess ends up on the wrong board for delivering check. But when Ne5 would have started on the other board, the line from the orthodox study would work just as well. Problem is that the Knight cannot triangulate, so you cannot get it to the same square in an odd number of moves to swap boards. So you should somehow force the black King to triangulate.

The problem in the Troitsky study is that the mate is really occurring in the wrong corner, far away from the Pawn, so that the other Knight (which must keep blocking the Pawn until the mate is only two moves away) cannot be used in the confinement, and you have very little control over what the black King does. So if there is a winning strategy here, it must be through driving the bare King to h1 wint King plus a single Knight, making use of the fact that f1, f3 and e4 form a no-go area for the bare King. In that corner you could use the 'free' Knight to guard h3, while moving Kg3-f2 to effectively lose a tempo:

I am not sure whether this will be possible. (And it also depends on whether the bare King arrived in the corner on a board where Nf3 would check it, or black would not be forced into the corner, but would advance his Pawn.) It would be interesting to generate End-Game Tables for Alice Chess. Since the Alice board has 2x64 cells, this would be harder than for orthodox Chess: each extra chess man gives another doubling of the size. For checkmating a bare King it doesn't matter on which board the other King is, though. So tables for end-games like KBNK are 8-times larger than for orthodox Chess.

seems I inadvertantly deleted too much in the latest patch; the routine Illegal(), which tests legality, was no longer called at all.

I fixed that now.

This is natural logarithm (base e). So ln 2 ~ 0.69, i.e. 69 elo for a speed doubling.

This is for engines playing orthodox chess, and seems to be quite universal. (Except when the level of play gets so high that almost all games end in a draw; then doubling the speed doesn't give so much Elo gain anymore, because even a perfect player can only beat a weaker player when the latter makes an error.)

This page is just for presenting an external link, and such pages should not contain much other info. The content at the link should speak for itsef. Of course you can create a new page for Chesscraft that would contain an extensive description. (Through https://www.chessvariants.com/index/membersubmission.php )

However, I discovered a new bug where any piece that makes a move to a non-highlighted square will burn/move/make pieces. The squares that get affected are a bit unpredictable though. This also appears to apply to diagrams where the spell parameter is not set, such as this one.

This should be fixed now too. It was a consequence of the partial revert of the legality patch, which moved the 'scoring' back to after the move was selected, instead of scoring each move in the move list. But illegal moves are not in the move list, and one is synthesized based on the origin and destination click when no move in the list that satisfies the clicks is left. I had forgotten to remove the scoring of that synthetic move, so that it was scored twice. The first scoring replaces the 'no promotion' code 0 by the encoding of the piece itself. But the second scoring then interprets the 'has moved' bit of this piece as the encoding of a burn. What exactly gets burned is then determined by the type number of the piece.

No, it would require some extra programming. But not very much.

I suppose I wrote that because it defines three King types. But it appears to use the correct ones, so perhaps I was too pessimistic.

Anyway is the transferrer an interesting concept, or the joker should be enough even in this context?

Well, I dislike Jokers to begin with, so perhaps I am not the right person to comment on this. In principle you can make this as complex as you want: not imitate the piece that was moved, but for each possible type define the type the Joker should move as independently. This way you could also define partical imitation: e.g. if you want to disallowe.p. capture and double push when imitating Pawns, you could define a (no-participating) Pawn without these moves, and ilet the Joker imitate that when a Pawn is moves.

This could be implented by having the user define an array to map (moved) piece types onto (imitated) piece types. In the code you would then simply replace "imitated = movedPiece" by "imitated = transfer[movedPiece]". By default the transfer array would map every type on itself.

I finally understand what is the problem here. There actually was an avelanche of bugs, some stupid (like accidentally masking off the color bit, or forgetting to mask the 'also burns' bit from the code of the promoted piece), and some more fundamental (introduced by the legal highlighting). The stupid ones are fixed now, so that black promotes to black pieces, and the promoted piece does show up on the purple squares.

The problem with the spurious burning is more fundamental, though: the NewClick input routine combined all moves with the same step to a single one for highlighting, making a list of all posible promotion choices for that move. This was fine when burning was only indicated by a different code for the promotion pieces, as it is when the pseudo-legal moves are first generated. Before the moves can be used they are 'scored', however, which also includes identifying which pieces get burned, and writing those into the move as extra locust squares. This used to be done after the user had selected the move and promotion pieces.

But for the legal highlighting it has to be done for all the moves of the selected piece, to make those in order to test legality even before the user selects one. But this interferes with combining the promotion choices when one of those would burn, and the other not. I am not sure yet how to solve this. It is conceivable that one of the promotion choices is legal, and the other not. (E.g. because you burn a piece blocking a slider attack on the King, or fail to burn a hopper mount.)

It seems to me the snout still has too much of an up-curve near the nostrils. I also don't understand why it 'dresses' the horns near the base; most Wildebeest pictures I have seen have the horn run all the way to the skull. It is true that the way the horns attach to the skull is much better here.

For me the archetypal Wildebeest is this:

Colors are a drawback when you don't use marker symbols for highlighting the possible moves.

I agree the I.D. in the article is not very pleasing aestethically, and having two diagrams of the initial setup is redundant. It would be better to replace the first diagram by an identically looking I.D.. Perhaps I will do that one of these days.

An interesting case is a Bishop that also attacks the square right in front of it, but cannot move there (BfcW). On 8x8 about half of the positions is won. Which is an intermediate value. It appears there also is a fortress draw here: once the bare King reaches the back-rank corner of the other shade than the (augmented) Bishop is on, there is no way to smoke it out. Since the Bishop cannot attack that corner, the King can always return there after zugzwang forced it to leave it; as long as the bare King stays on a square adjacent to the corner the other King cannot attack that square either.

If we also add a color-switching move (e.g. BfW or BfcWbmW), all corners can be attacked, and nearly all positions are won.