The Retrograde Analysis Corner

Space Chess

Glossary

Space chess is played on a 5x5x5 cube. The beginposition looks like this: (E is the top board, A the bottom board):

[rnknr/ppppp/5/5/5] E [buqbu/ppppp/5/5/5] D [5/5/5/5/5] C [5/5/5/PPPPP/BUQBU] B [5/5/5/PPPPP/RNKNR] A

The pieces, and their movement:

The king may move one square into any direction. A king on Bb2 (b2 on board B) can go to 26 different squares: the a1-c3 square on board A, the a1-c3 square on board C, and the a1-c3 square on board B, minus b2.
The queen may move any number of squares into any direction.
The rook moves along straight lines in the slices it is in. For instance, a rook on Cc3 is in the [A-E]a3-e3 slice, in the [A-E]c1-c5 slice, and in the C-slice. It moves like a 2D rook in any of these slices.
The bishop moves like a 2D bishop in the slices, defined for the rook.
The knight moves like a 2D knight in the slices, defined for the rook.
The pawns move one square towards the 5th line on the board it's in, or towards the E-board in the vertical slice it's in. Capturing can be done in the board the pawn is on (one square diagonal, in the direction of the 5th row), or in the vertical slice, parallel to the first line, it's in, but not in the slice parallel to the a-line!
The unicorn (the turned knight in the diagram) moves like a 3D diagonal piece: A Unicorn on Bb2 can go to Aa1, Cc3, Dd4, Ee5, Aa3, Cc1, Ac1, Ca3, Ca1, Ac3.