CubeChess

What is this?

The core idea here is "chess played on a rubiks cube"

Equipment

A custom 4x4 rubiks style cube. It should be checkerboard to be only two colours overall, with the corners being the same colour on all three faces, and edges being the same on both. It should be tinted on opposite faces (eg: dark green and light blue on one face, and dark red and yellow on the opposite. The other four faces would be simple black and white ("no man's land")

Edge and corners are a single "location" for the purposes of gameplay - meaning there are 56 positions total on the board.

https://www.gamesworld.com.au/product/mefferts-checker-cube/

https://www.gamesworld.com.au/wp-content/uploads/2023/03/CHECKERS2.jpg

Rules

Setup

The green and red faces are the "home" sides for each player, and is never directly seen by their opponent. Each player thus plays with visibility of only 5 faces of the cube. Information about the 6th may be discovered, see gameplay.

On the home face, the 16 traditional chess pieces are arranges thus:

• A pawn on each corner (4 pawns total)
• A pawn on each edge, two on black and two on white. However, the choice of exact which two white and which two black is up to the player. (blacks may be on adjacent faces, or on opposite faces)
• Pawns are positioned on their edge and corner pieces such that they are on the no man's land part of their location, and visible to their opponent.
• The 8 backrow pieces fill the remaining 8 positions (four center, and four of one per edge) with the following constraints
  • King and Queen must next to each other (thus on opposite colours) within the center four
  • The pairs of Bishops, Knights and Rooks must have one each on opposite colours to each other
  • These backrow pieces all begin on the home-face, including those on the edge.

On setup, each player thus knows where all their opponents pawns are, and thus which edge locations contain powerful pieces, but does not know what those pieces are.

Gameplay

• Pieces have no requirement to stop at an edge or corner. All faces of those are treated as the same location, and in general, moving across the edge or corner should be straight forward

• Note: This game has no castling (no obvious way to make it work) or en passant (
  • Promotion? Even the center-four of the opponent's home face is closer than the traditional back row. However it's not visible. Gameplay to determine if Promotion is a good or bad idea.
• Pawns move forward towards the opposition home side one move at a time, to an opposite colour, or take a piece by diagonal to the same colour. Their opening move may be a double-fowrward to the same colour.
  • Pawns may also defend their home row (in fact a circle) by a modification of en passant. If an opponent reaches the pawn row next to a pawn that has not yet moved, then that pawn can move diagonal behind that opponent piece, to take it. The motion is equivalent to en passant, but where en passant is a battle-proven pawn taking a fresh pawn who moves double, this is a fresh pawn taking any piece that arrives beside it by any motion.
• Bishops move as traditional - colour locked on a diagonal. When they reach a corner, they can continue along either alternate face.
• Rooks move as traditional - straight lines, travelling across alternating colours.
• Knights move as traditional - forward+across, landing on an opposite colour to their origin. Due to the nature of the cube, it's possible for knights to move to a position next to where they began.
• Queen moves as either a Bishop or a Rook.
• King moves as per Queen, but distance limit of one.

The above piece movement rules places unusual emphasis on the colours a piece encounters, due to the following...

On each move, a player may move a single piece (like chess), OR make a rotation of a row/column of the cube (like solving rubiks). A rotation of part of the board can result in the checkerboard pattern being broken, thus creating obstacles to all pieces due to breaking the "stays on same colour whilst diagonal" or "alternates colours as it moves in a straight line" and so on. It's expected that Knights may benefit most from this situation, though they will still be required to land on a colour opposite to their start.

Cube rotations are limited thus:

• A players home face is the one that faces them, regardless of the composition of the colours of the locations on it.
• No rotation make take a location coloured as part of a players original home face, into their opponents home face.
  • Note that it's technically possible for players to coordinate their turns of the cube such that all their home-tinted locations move into no-mans-land, and then rotate so they are adjacent to each other. This does not impact what is their home face, which only ever has four pieces rotated from it.
• A player may "undo" the rotation made by the previous player, after which the original player may not redo it again.

Further rules

• Border crossings:
  • No piece may cross the border from their own coloured home face, to no-mans-land, and then across a second border to the opponent's coloured home face, in a single move. This negates the ability of a first-move attack directly into the opposition home territory. In regular chess, it's impossible to move to an opponents two home rows any faster than 3 moves (Queen, Bishop, Knight, with Rook and Pawn requiring four moves). The one-border-limit here creates a limit of 2 moves minimum for every piece.
• Fog of War
  • the opponent's home face (16 locations) is a fog of war. Suggestion is that if a player has a piece in no man's land on one side, then the fog is lifted for the opponent's edge. This is easy to visualise since edge and corner pieces are a single location with multiple orientations, so the fig is lifted by reorienting the pieces into visibility. This is not a move to do so.
  • The center four locations remain unavoidable fog of war. In any physical game, check into those locations must be done by trust. In a computer implementation, the algorithm can handle that.

End game

Forcing checkmate may be difficult given the cube rotation possibility. Playtesting will be required to determine if this is a viable winning condition, or if an alternate is required. Some thoughts to consider:

• Restrict cube rotation from being used to escape check
• Perhaps require the king to be in no-mans-land to

Origin

This game came about from a photo of chess pieces on a pair of 3x3 rubiks cubes together.