Platonic Chess
Platonic Chess is played on a 10x10 board. It consists of ten chess pieces based on the five Platonic solids, and a row of ten Pawns on the third rank.
Setup
Pieces
Pawns
There are ten pawns at the third rank, and they move as in Orthodox Chess.
Platonic Solids
There are two duplicate pieces for each Platonic solid type. The moves for each Platonic solid piece are as below:
Tetrahedron
A tetrahedron has 4 surfaces, so it can only reach 4 squares.
It moves one square orthogonally like the Wazir.
It is a royal piece like the King in orthodox chess, and can be put in check.
Cube
A cube has 6 surfaces, so it can only reach 6 squares.
It moves one square diagonally like the Ferz and slides up to two squares forward.
Octahedron
Octahedron has 8 surfaces, so it can only reach 8 squares.
It moves diagonally like a Bishop , but only up to two squares.
Dodecahedron
Icosahedron
Rules
Promotion
A Pawn can capture as a Platonic solid piece in addition to its original moves upon reaching the enemy side:
- 1st rank - moves and captures as a regular pawn, can also capture as a Tetrahedron
- 2nd rank - moves and captures as a regular pawn, can also capture as a Cube
- 3rd rank - moves and captures as a regular pawn, can also capture as an Octahedron
- 4th rank - moves and captures as a regular pawn, can also capture as a Dodecahedron
- 5th rank (last) - moves and captures as a regular pawn, can also capture as an Icosahedron
The Pawn's additional capture ability is linked to the enemy rank it is on, and is not cumulative. A promoted pawn can only move passively as a regular pawn, and capture one square diagonally forward. It can also capture as one of the Platonic solids depending on which enemy rank it is on (see above). When a promoted pawn moves away from the enemy side by capturing as a Tetrahedron backward, it reverts to a regular pawn.
When a pawn reaches the last rank, it can no longer move or capture forward. Its only legal move is to capture up to four squares orthogonally backward or leap exactly two squares backward. Therefore, unlike in orthodox chess, pushing a pawn to the last rank may not be the best strategy, and it could be advantageous to keep the Pawn in another rank in the enemy side, depending on the positions of the pieces on the board.
Castling
A Tetrahedron can perform the castling move with an Icosahedron on the same side. The final position is the same as the positions of the equivalent pieces (King and Rook) after Queenside castling in orthodox chess.
Checkmate
The game is won when either Tetrahedron is checkmated.
Fork Checkmate
When both Tetrahedrons are forked by an attacking piece, this effectively ends the game since the two tetrahedrons cannot be moved away from check at the same time. A Dodecahedron can easily fork the two Tetrahedrons if they are right next to each other or one square apart orthogonally or diagonally. An Octahedron or Cube can also fork the Tetrahedrons if they are one square apart orthogonally. An Icosahedron can fork the Tetrahedrons if it lies between the two in the same rank or file, or when it is exactly one square apart orthogonally (or diagonally) from one Tetrahedron and one square apart diagonally from the other Tetrahedron. Checkmate can only be avoided in these cases by capturing the attacking piece.
Skewer Checkmate
If the two Tetrahedrons are skewered by an Octahedron along the diagonal and it cannot be captured in the next move, the game is also won. A skewer by an Icosahedron when the Tetrahedrons are next to each other orthogonally can be blocked if it is one or two squares away.
Notes
How to play using commercially available equipment
You will need:
- 1 x International Checkers set with a 10x10 board
- 1 x Chess set (Optional)
- 4 x Platonic dice set
The chess set is optional since checkers pieces can be used as pawns on the Platonic chess board.
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By Albert Lee.
Last revised by Albert Lee.
Web page created: 2021-06-26. Web page last updated: 2021-06-27