Chess in the Third Dimension is a clean, simple, elegant application of
traditional European chess to the third dimension. The goal - checkmate - is the
same as in the traditional game, and the same pieces operate on the same number
of squares with the same (almost) moves as in the traditional game. It is quite
simple for players of 2-D chess to learn, though playing it well represents a
new challenge. It has been moderately play-tested and seems to take about the
same amount of time as 2-D chess. It's fun, but it doesn't have the gimmicky or
contrived feel that many attempts at three-dimensional chess have. The rules
generally conform to those of traditional chess, which will not be
repeated here except where differences or clarity require.
I created Chess in the Third Dimension in 1980 but this is the first
setting-down of its rules and it is therefore Copyright © 1996 by Lawrence
Sulky.
The Equipment
The board and the initial placement of the pieces are shown in the
accompanying diagram: 
The board consists of four levels, numbered I to IV from bottom to top. The
columns and rows of each level are labelled as shown. Each level overlaps the
level above or below by two rows or two columns, so that one quarter of
each level overlaps with one quarter of all the other levels. This 2 x 2
quarter is marked in heavy lines in the diagram.
Note the position of light and dark squares on each level.
Physically, the levels are typically mounted on a post that runs through the
centre of the four squares (heavily outlined in the diagram) that overlap on all the levels. The levels are placed
far enough apart that the pieces and the human hands that move them can readily
fit. The squares themselves are transparent or translucent for better
visibility.
A standard chess set is used, arrayed initially as shown in the diagram.
Note the colour of the squares of the queens and kings.
The Moves
In general, the pieces move as they do in traditional chess, but with the
third dimension incorporated into these moves. For example, the bishop moves
diagonally, meaning that it moves through the corners of the squares and, as a
result, always stays on the same square colour. But in our three-dimensional
view, the squares are actually cubes, and the bishop moves through their edges,
as opposed to their sides (like a rook) or their corners. The following diagram
illustrates the moves of the bishop, rook, and knight, from which the moves of
all the other pieces can be deduced. After the diagram, all the pieces' moves
are described in detail. 
Note: A general rule is that pieces cannot move across a gap between levels. For
example, to move from level II to level IV, a piece must traverse at least one
cube on level III.
Now, a detailed description of each piece's move.
Rook
The rook moves in a straight line through cube faces - that is, forward and
backward, side to side, or up and down.
Knight
The knight moves through one cube face and one cube edge, in either order,
in such a way that it ends its move more than one cube-width distant from its
starting point. Note that this effectively permits a move through a cube corner.
The knight may move through other pieces (but, like any other piece, it
may not bridge a gap between levels).
Bishop
The bishop moves in a straight line through cube edges - that is, diagonally
across a single level, or diagonally upward or downward through levels.
Queen
The queen combines the move capabilities of the rook and the bishop.
King
The king moves like the queen, but only one cube per move.
The king may also, as its first move, castle with a friendly rook, provided
that that rook is in a friendly rook's starting position. Castling is
done
in one of two ways. For White: (a) move the king to IIIc1 and the rook
from IIId1 to IIIb1; or (b) move the king to Ic1 and the rook from Ia1
to Id1. For
Black: (a) move the king to IIb4 and the rook from IIa4 to IIc4; or (b)
move the
king to IVb4 and the rook from IVd4 to IVa4. In castling, neither king nor rook
may jump over another piece. The king may not castle out of or into check. In
addition, it may not cross a cube that is under attack by an enemy
piece; for White, this could only be cube IIIb1, and for Black, this
could only be cube IIc4.
Pawn
The pawn moves like a rook and captures like a bishop, but only one cube per
move, and only forward. Forward is defined as "toward the enemy starting
positions". This means that, once a pawn has changed levels, it cannot
change levels again, either up or down; that would place it on a level where its
own side started, and would be considered a move back toward friendly lines.
However, the pawn can move "sideways diagonally" upward or downward,
from IIIa4 to IIb2, for example...but only once.
A pawn that reaches a cube in the far rank of the enemy starting positions
can be immediately promoted as in traditional chess. This
means that white pawns can only be promoted on rank 4 of levels II and IV, while black
pawns can only be promoted on rank 1 of levels I and III.
The pawn does not have a double first move as in regular chess, and
there is, therefore, no en passant capture. |
