## The Rules of 3D Chess

There are actually four slightly different games of 3D Chess.

None of them is either a "more official" game, or a better or worse game, than the others; they are alternate games.

These games differ only in their rules for the moves of the Pawn and Knight.

All of them have the same set of rules, as follows:

### The Common Rules of All Four Games

1. The standard rules of FIDE Chess apply except as follows.
2. The playing field is an 8x8x8 cube instead of an 8x8 square.
3. All squares in a single vertical stack are of the same color: for example, a1 is a black square on each of the 8 8x8 levels.
4. The standard algebraic notation is modified by the addition of the level number which is prefixed to the name of each square. Thus, the bottommost square a1 is 1a1, and a1 on the top level is 8a1.
5. Eight standard chess sets are used. Each player has the standard Chess lineup on each of the eight levels.
6. The Kings on 4e1 and 4e8 must be distinguished from the others in some obvious way. Rules about check and checkmate apply to only these two Kings; the other Kings are not royal, and in fact are called Commoners.
7. Castling can involve Kings and Rooks from different levels.

It is obvious that from 4e1 the White King can Castle to 4g1 bringing the Rook from 4h1 to 4f1; after all, this is all on the same level so it looks like FIDE Chess.

Equally obvious, "from 4e1 to 2g1 with 1h1", "from 4e1 to 6g1 with 7h1", "from 4e1 to 4c1 with 4a1", and "from 4e1 to 6c1 with 8a1".

However, "from 4e1 to 2c1 with 1a1" is a special rule: it really ought to be "with 0a1" but there is no level 0.

Vertical Castling, for example "from 4e1 to 6e1 with 8e1", is not allowed.

The notation for Castling "from 4e1 to 2g1 with 1h1" is "O-O(2g1)", in other words, we give the King's destination position as part of the move; this can be omitted if only one O-O is possible.

8. The normal two-dimensional moves of the pieces are translated into three dimensions in the following manner:
Rook
A Rook makes a standard Rook move, or moves straight up and down, or rises or descends as it makes a Rook-move. For example, a Rook on 1a1 can (if nothing is in the way) move to 8a8, passing through 2a2, 3a3, 4a4, 5a5, 6a6, and 7a7.
Bishop
A Bishop makes a standard Bishop move, os rises or descends; for example from 1a1 to 8h8 via 2b2, 3c3, and so on.
Queen
The Queen combines the powers of the Rook and Bishop.
King (or Commoner)
The King and the non-royal King which we call the Commoner move as the Queen, but just one square at a time.
Pawn
Pawns may only move straight forward on the same level; that is, their move is one-dimensional. The rules for Pawn capture are different in the different games.

Knight
The rules for Knight moves are different in the different games.

## The Shortest Game Possible

1. 4e2-4e4 4e7-4e5 2. Q4d1-4h5 K4e8-4e7 3. Q4h5:4e5 mate

The normal foolsmate does not work in 3D, but this pretty mate can be accomplished in 3D using seven different White Queens, one of which has 3 routes. (You might want to check and see if I'm wrong.)

This is the shortest game ending in checkmate for all forms of 3D Chess.

## Pawn Power In Chess

In two-dimensional Chess, each square of the board can potentially be attacked by at most two Pawns, so that every time you advance a Pawn you need to think carefully about the squares for which you have weakened your potential for Pawn control.

Another major attribute of Pawns is that they run into each otehr and form immobile chains that define the strategic terrain.

Both of these considerations are very important to the feel of Chess, it is impossible for either to remain exactly the same in 3D Chess as in 2D Chess, and it is necessary to be very careful about how these things change.

## Four Different Games

Mixed 3D Chess uses the Knights and Pawns from the mathematical mapping.

Upright 3D Chess uses "upright" Knights and Pawns.

Flat 3D Chess uses upright Knights and two-dimensional Pawns.

Very 3D Chess uses purely 3-dimensional Knights and Pawns.

## Rating the Games

These games may be equally good, but certainly are different.

Upright 3D Chess should be very easy to learn if you are already a 2D Chess player.

Mixed 3D Chess attempts to be the most balanced, and Flat 3D Chess has very special Pawns.

Very 3D Chess is very three-dimensional.

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