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Chess 66©


What’s new in Chess 66? The game board has a new geometry. It is based on the 8×8 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:

  • There is a change in line between the lower and upper half of the board, for example d4 to e5;
  • there is a change in the diagonal in the same way, for example d4 to f5;
  • The white player still has a white right corner field, while the black player now has a black right corner field.

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.

  • A move can be made ‘forked’ over a switch (see Fig. 5), whereby far more squares can be reached with one move than the queen and rook can do in normal chess.
  • From line a1/a3, the rook and queen can either occupy square 4 or a4 or further on occupy either line a5/a8 or line b5/b8.
  • Queen and rook can thus checkmate an opposing king standing for example on a8 starting from line a1/a3 without the help of other pieces. Queen and rook have strong positions on lines a1/a3 and h8/h6.

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:

  • The squares of the switches (4/a4 and h5/5) are independent squares and must be played separately.
  • The a4 and h5 squares do not differ from the corresponding squares in normal chess.
  • The new squares 4 and 5 are composite squares as described and consist half (triangular) of square a4 or h5 and the new triangles due to the board geometry.
  • Squares 4 and 5 are equal to all other squares and must be played independently as described;
  • The position on the Switches must be clear. Either field 4 or field a4 must be occupied. This applies to field 5 or field h5 in the same way. The player must show this by clear position of his piece.
  • The Switches can be occupied by only one piece, because with two pieces on a switch, each piece claims half of the other square, which contradicts the independence of squares. In addition, it would then be conceivable that a switch is occupied by one of the player’s own pieces and at the same time by an opponent’s piece, which means that opposing pieces are partly on the same square.
  • On a Switch, a piece will be captured on the field on which it stood. This would be field 4 or field a4 for one switch or field 5 or field h5 for the other.
  • move between field 4 and field a4 or between field 5 and field h5 isn’t possible. In the row the next field which can be reached by 4 is field b4 (g5 by 5) (illustrated below). This has a simple reason: A change between squares can only take place if the squares are different. But the squares of a switch are only partly different, half of them are equal. So it is not possible to switch on the same square or partly on the same square.
  • Occupying a square of the switch closes the switch for the move over the switch. Therefore, a piece on 4 prevents the move a1-b8. Why is that? This is because the second square of the switch is half occupied. It makes no difference whether a square is completely or only half occupied. In both cases it is not possible to move over a completely or half occupied square.

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

  • A rook/queen can occupy square 4 or a4 from a1/a2/a3 or move immediately to a8 or b8;
  • A bishop on d1 can occupy square 4 or a4, or move immediately to a5; from 4, it can move further up to e8, by which the bishop has changed its color diagonal;
  • A rook/queen on rank 4 (e4, for example) can occupy a4 or 4 in the switch;
  • A bishop on e8 or a rook/queen on a8 or b8 can also reach square 4 or square a4 in the switch and capture an opponent’s piece there; the opponent’s piece then stands on the square of the captured piece.
  • Finally, you can move into a switch from below, from the side or from above. If the switch is not occupied, then you can choose whether the piece that moves into the switch is on 4 or a4 or 5 or h5 after the move. If the switch is occupied, then the piece in the switch must be captured; the opponent’s piece takes the place of the captured piece.


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.


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