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This page is written by the game's inventor, Gerd Degens.

Chess 66

What's new in Chess 66? The game board has a new geometry. It is based on the 8x8 board of normal chess with 64 fields, but with the difference that the board now has 66 fields. This apparent contradiction is resolved by halving the playing field in the row, shifting one half by a line, realigning the two halves geometrically and adding two new fields. The new fields are fields 4 and 5.

The changed geometry means that triangles are created to the left of a4 and - from the point of view of the white player - to the right of H5, which are included in the board. Then the fields a4 and h5 are 'virtually' halved. This lays the foundation for fields 4 and 5.

Field 4 is made up of the triangle to the left of a4 and the lower left - also triangular - half of field a4.
Field 5 is made up - from the point of view of the white player - from the triangle to the right of h5 and the upper right - also triangular - half of the field h5.

Finally it should be mentioned that due to the new board geometry:

At first it looks like a geometric gimmick. But it is not - to make it short:

The king can be checkmated with one piece.
The bishop can change his color diagonal.

How is that possible?
Let's start with the statement that an opposing king can be checkmated with one piece and let's look at the squares 4 and a4 as well as 5 and h5.

The Switches

4 and a4 as well as 5 and h5 are switches. Switches enable moves that do not exist in normal chess and that primarily affect the pieces queen and rook.

Now to the statement that a bishop can change his color diagonal:

That means that a bishop remains on his color diagonals during the game in the normal chess. A white bishop always moves on white diagonals and a black one on black. Opposing bishops on different color diagonals cannot attack each other in the course of the game. In principle, this is a 'loss' for the game of chess.

The Transfer Fields

For the Bishop to change color, it must be able to transfer from squares of one color to squares of the other color. While this is not possible with the traditional squares of normal chess, the transfer fields in Chess 66 do make this possible.

Fields 4 and 5 are called transfer fields, as can be seen by the double color scheme. Transfer fields allow moves that do not exist in normal chess. This is especially true for the bishop and the knight.

But we are not quite finished with that. A few rules are added to the well-known rules of normal chess in Chess 66

First of all, it should be mentioned that, in contrast to standard chess, in Chess 66 only the queen and rook pieces face each other on the same line in the initial position - apart from the pawns.

The Rules

Concerning the switches, the following rules must be observed:

Here are some moves examples, which explain the handling of the switch:


Last but not least, the knight demands our attention:

In normal chess, the knight moves to one of the fields that are closest to his starting field, but not on the same rank, file or diagonal. He does not move over the fields in between.
Due to the changed board geometry, an addition to the FIDE rule for knight moves in form of a specific definition for determining the field distances is necessary. It comes from Alfred Pfeiffer (Chemnitzer Schachverband e.V.):

The knight moves to one of the squares that a king can reach from the square in two moves, but which are not on the same row, line or diagonal. It does not move across squares that lie in between.

Sounds complicated, but it's actually simple and self-evident. This should be illustrated with an example. In Fig. 10, the knight starts from square 5. With the FIDE definition for the knight move, squares g7, f6 as well as f4 and g3 can be reached without any problems.

In Chess 66, you can also occupy the e4 square, because e4 can be reached from 5 with two king moves - first via g5 (see the rules above), then to field e4.

Another example: A knight starting from 4 reaches square b6 via a5/a6. If the knight starts from a4, it reaches square a6 via b5/b6. If the switch were seen as a unit, the described moves could not be executed, because the start and end squares are on the same line.

A special constellation is the following: A knight starts from a3. Square b5 is reached via 4 and a5. If the path via a4 and b5 is chosen, a5 is occupied. These moves are consistently excluded, because start and end square are on the same line, which is not in accordance with the rules.

This 'user submitted' page is a collaboration between the posting user and the Chess Variant Pages. Registered contributors to the Chess Variant Pages have the ability to post their own works, subject to review and editing by the Chess Variant Pages Editorial Staff.

By Gerd P. Degens.

Last revised by Gerd Degens.

Web page created: 2022-02-26. Web page last updated: 2022-07-24