Comments/Ratings for a Single Item

During a recent game at SchemingMind, the subject of the weakness of the
Alice Knight brought forward an interesting possible variation to the
rules.

Allow the Knight to capture on both fields.  In additions to the standard
capture move, it would be allowed to capture the destination cell of the
opposing field.  It would still only perform a single capture during a
move, and still be bound to one-half of each field.  And it would still be
restricted from moving to a friend-occupied cell.

This increase in power would greatly improve its influence in the game.

Unless this variant rule has been previously proposed, I suggest that it
be called Alice Knights.

This game definitely challenges the player's ability to extrapolate
positions.  Keeping track of the oscillation of every moved piece and
maintaining some form of strategy, the player is fortunate to be able to
plan more than several moves.

This is also the joy of the game.  A player who desires an easily
comprehensive form might well be warned about the dangers surrounding this
game.  But they should not fear to attempt it.

My favorite variant is the Mirrored Alice set-up, whereby opposing pieces
begin on seperate fields.  This offers a large variety of opening moves.

It was Jellis, not Parton, who said 'it is usual to forgo it.' This is a
crucial point, because Parton, not Jellis, is the inventor of this game.
If Parton had said it, we could safely assume that Alice Chess has no en
passant, but Jellis does not speak of the game with anything like the
authority of its inventor.

I'll look at the page on Passar Battaglia later. I'm not up on the term
and cannot comment on it at this time.

The application of en passant in Alice Chess is really not that confusing.

The opposing Pawn must have immediately performed a two-step move to the
capturing Pawn's field, resulting in a position orthogonal adjacent.  The
cell which the capturing Pawn is moving to must be vacant, in both fields. 
This denotes that the single step was a viable option for opposing Pawn.  

If that cell on the capturing Pawn's field is occupied by either friend
or foe, en passant is not viable since the single step of the opposing
Pawn was not possible and thus capture of that Pawn on that cell was not
an option.  If it is occupied by an another enemy, a simple capture of
this enemy piece is still possible but this would not result in the
capture of the opposing two-stepping Pawn.

hmm this place is a bit frisky lately, anyway, i'm going to rate some
unusual games, and what better place to start than here. 
This is an amazing game, no need to say anymore. Highly original,
strikingly beautiful concept.

En Passant

While reading through the various discussions on en passant in Alice Chess, I came up with an option not mentioned that seems to be quite consistant with the core rules: When making an en passant capture, it's irellevant if the destination square on the board of the capturing piece is occupied, as the pawn really ends up on the other board, which is open.

This satisfies the three main rules:

1. A move must be legal on the board where it is played: By standard Chess rules an en passant capture is allowed when a double pawn move places a pawn adjacent to an enemy pawn.
2. A piece can only move or capture if the corresponding destination square on the other board is vacant: In order for the captured pawn to have made a double move, this must be true.
3. After moving, the piece is transfered to the corresponding square on the other board: This applies as normal.

This interpretation may seem strange, but it's entirely internally consistant. The standard chess en passant rules have no provisio for the destination square being occupied because it's impossible. I propose Alice Chess ought to have none, because it's irrellevant (unlike other variants where this issue is raised).

The other interpretation (that the destination square must be empty) really only makes sense if paired with a rule that makes double pawn moves illegal is such cases. In which case, the supposed ambiguity is, once again, not possible. However, I don't really like this option.

Firstly, it adds additional complications to the rules. With all other moves, legality is determined by the state of board the piece starts on. However, the legality of double pawn moves is dependant on both boards.

Secondly, the basis of this rule is that a double pawn move basically two seperate moves. If that was the case, in Alice Chess the pawn would end back on the board it started on. (Which could be an interesting option. If you handle en passant as I suggest, it works.)

Check

While there seems to be no special mention of check and mate in the rules on this page, it seems to me that it ought to be handled as normal. In other words, the king is in check if it could be captured on the next move.

Since Alice in Wonderland is currently in the theaters, I thought it would be a good time to make a video about Alice Chess.

Well here's another approach to En Passant. Given that this is a special move comprising two 'normal' Pawns moves, should it be treated as such, with the first step taking it from its starting board to the other board and the second bringing it back? Were this the case an enemy Pawn capturing En Passant would have to do so as if the Pawn being captured, now back on the starting board, were on the other board having made only the first step. A question that follows is what about Castling, whose bar on moving can also be seen as a form of En Passant - and again the King makes two of its 'normal' moves.
	On the issue of the film, is anyone else surprised that in this age of gratuitous sequels the film conflates two quite distinct stories, even going beyond previous films in this respect by conflating two queens? You would think that this would be a golden opportunity to make two films, one for each book. Through the Looking Glass in particular has its own distintive (chess-related) plot structure that gets lost when the two storylines are merged.

A pretty playable subvariant would be with both boards full, and ordinary moves, starting and ending on the same board, by necessity, legal.

You could even adapt the mechanic for higher dimensional games, with layers of boards, with the rule that for a piece to move legally from one board to another, the move would have to be legal on all intermediate boards aswell...

I made a dedicated derivative of Fairy-Max to play Alice Chess. It uses the method of a single board with 'pedestals', i.e. it uses the same coordinate notation on both boards. This to make it playable in a GUI as if it were normal Chess, when you switch legality testing off. (The GUI will see moves jumping other pieces, that in reality are on the other board, and would not think these were legal...)

The engine can be downloaded from http://hgm.nubati.net/Alice.zip , and can work under WinBoard.

I might some day equip WinBoard with special support for Alice Chess, so that the user can actually see which piece is on which board.

The Alice version of Fairy-Max does not have e.p. capture. It has castling, but I am not sure what it considers 'passing through check', and for Q-side castling also b1 has to be empty. Normally this should not be a problem.

The rules of Alice Chess suggest each move is to be considered a multi-step move, the transfer between the boards being the final step. Otherwise there is no logic in the requirement that you must not move the King to a square that is attacked on the board it came from, but can stay as long as you want on a square that is attacked on the other board. So if there were e.p. capture, I think that it should be possible to capture a Pawn that just moved on the board it came from, even if it did not do a double-push. (And of course you can always capture it on the board it ended up on.) It does not seem that the game was intended to be played that way, however, so it would be logical to forbid any form of e.p. capture.

Alice Chess is a 3D chess variant that works very well, with only minor trickery required (i.e. that no piece is allowed to occupy the corresponding square on the opposite board). Not only that, but interesting exchanges of differing piece types can still be made, with there still being a variety of 'major' and 'minor' pieces.

Beautiful.

What a great classic variant I've only recently discovered!  This description mentions that you can use only one board.  I agree and think it's easier visually. After each piece is moved, you could just mark it with some sort of large poker chip underneath (or clip something onto the top) and vice versa - when a marked piece is moved it loses the marker. 

Then, the players could simply have an understanding that marked pieces and unmarked pieces are not in each others' way and cannot capture each other.  So a game could go like this:

1. d4  Nf6

(now the white pawn and black knight are both marked)

2. Qd6 now possible for White because White knows the unmarked Queen can go "through" his/her marked pawn.  Then the Queen becomes marked at d6, threatening the marked Black knight.  The Black knight then moves to e4 and loses its marker. 

This is a trial for using the Interactive Diagram for Alice Chess. Custom-supplied functions BadZone and WeirdPromotion take care of refusal of moves to squares of which the mirror square is occupied, and take care of shuttling the moved piece to the other board, respectively. The boards are separated by strip of 'hole' squares, which has to be two files wide to prevent Knights from crossing it.

I implemented e.p. capture as a move by the Pawn on the board where the doubly pushed Pawn started. This seemed the least illogical way to do it, as the e.p. square on that board will always be empty (or the double push would not have been allowed). And it is the square the double push really passed over, and thus where it could have been blocked. The move could still be illegal because the corresponding square on the other board is occupied, but that is normal for any move to an empty square in Alice Chess that would be legal on its own board. There has to be no extra rule to prevent double capture this way. This method of e.p. capture corresponds to one where the doubly pushed Pawn must first make a single retrograde step before being captured, rather than replacing its double step by a single step. That this is not the same is the fault of an Alice double push not really being two consecutive single pushes.

I still have a comment to make about the legality of moves (an aspect that the diagram doesn't address). The ambiguity here seems to be caused by not making proper distinction between legal and pseudo-legal moves, but heaping them all under the term 'legal'. A more precise description would have said that a move in Alice Chess is pseudo-legal if (before transfer) it would have been pseudo-legal in orthodox Chess on the board where it is made, and the target square on the other board is empty. And then an Alice move is legal (as usual) when it does not expose the King to pseudo-legal Alice capture. This prevents solving distant checks by interposing a piece that was on the board where the checked King resides (but then disappearing to the other board, so that the King can be captured) from being considered legal. Despite the fact that they would have been perfectly legal orthodox Chess moves on the board with the King.