Alice-Raumschach

by Robert Price

The aptly-named Alice-Raumschach is the result of an application of the rules of Alice Chess to the classic 3-D Chess variant Raumschach.

Users of Zillions can grab my raum.zrf, which implements Raumschach and, as a Variant, Alice-raumschach; the picture below was captured from Zillions running this file. Users may find my rendering of the board counterintuitive at first (I did) - but use your imagination and pretend to be convinced by the 3-D illusion, and it'll grow on you. The board fits on the screen in 800x600 if you turn off the toolbar and search results.

Board and Notation

The Raumschach board consists of five levels denoted A, B, C, D, and E from bottom to top. The positions on each level are denoted a1 through e5, letters representing the files from left to right, and numbers, the ranks from near to far in the figure above. These are the conventions used by my Zillions implementation.

The crescent-moon pieces at Bb1, Be1, Db5 and De5 are Unicorns.

Moves

The initial layout and basic piece movements are identical to those of Raumschach. The game is won by checkmate; and stalemate is a draw.

The following are rules specific to Alice-Raumschach:

1. Immediately after a normal piece is moved, it becomes mirrored, and vice versa.
2. Normal pieces can only capture normal pieces, and mirrored pieces can only capture mirrored pieces. Exception: if the victim is the King, and it moved last turn, it may be captured regardless of its mirror status. (Naturally, this capture would never be effected -- the rule prevents a King from using the mirror transition to escape what would otherwise be checkmate.)
3. Mirrored pieces do not obstruct sliding Normal pieces, and vice versa. (e.g. a mirrored Pawn interposed between an enemy normal Rook and your normal Queen won't prevent them from capturing each other.)

In the picture below, I use red to represent White's mirrored pieces, and blue for Black's.

Strategy

Here's a short game, which was actually produced by Zillions. (Reassuringly, this was the only one of four or five that ended so quickly)

   White        |   Black
   -------------+-------------
1. nQ Bc1xEc4   | nQ Dc5xAc2
2. nU Be1xEb4   | mQ Ac2-Ac5+
3. nK Ac1-Bc1   | nQ Ac5-Bc5+
4. nB Ba1-Bc3   | nU De5xAb2+
5. mK Bc1xAb2   | mQ Bc5-Ad4+
6. nK Ab2-Ba1   | nQ Ad4-Da1+
7. nR Aa1-Ca1   | mQ Da1-Db2
8. mQ Ec4-Dc5 mate

Note that unmirrored pieces can only be protected by mirrored pieces -- which means that no piece is defended in the opening position. Here Raumschach is a little different from Alice Chess, because in Raumschach the starting position is such that you can capture on the first move. But that can be prevented by playing Mirrored Alice Raumschach, in which all Black pieces start mirrored.