3D Great Shatranj

This game is an attempt to present a simple, playable 3D chess variant which avoids or at least mitigates the worst of the problems of higher dimensional chess. It is the offspring of 2 of my previous games, Great Shatranj and Hyperchess, and my first straight up, no gimmicks, standard-type 3D chess variant. Like Hyperchess, the key to my design decisions is restriction.

Along opposite edges, the Guard, King, High Priestess, and Minister, with corners empty. In front of them, the Warmachines, kNights, and Elephants.

Above the pieces, pawns, on the 2nd and 5th boards.

Note this game is played "sideways" compared to most games on this site. This is done for ease of visualization. Promotion squares are now on the far right and left edges of the board.

Knights trace out their moves as 1,2 sliders. They have 2 paths to each destination square, and they can be blocked, just like any slider.

Let the leaping pieces stay in one big square and move little square to little square, or stay in one little square and move from big square to big square. This allows Parton's Sphinx cheat, with slightly different pieces: the 'bishops' move diagonally on the 'level' they're on, but orthogonally between levels. The elephants and towers can leap over an adjacent piece to their destination square, even when changing levels. This means the elephant may jump over 1 level orthogonally.

Note the knight is the only piece that may change both its position and level in a single turn.

The pawns are "forward-sideways only" wazirs, each a 3D wazir missing its "back down 1 level" and "backwards on a level" moves. So it has 4 of its 6 possible moves. It can move orthogonally "forward" or "sideways" on the board it's on, or it can move 1 board closer to the opponent's back rank. Pawns capture as they move, 1 square orthogonally forward or sideways. They cannot capture diagonally.

Note in this setup, white pawns all move up, down, and from left to right only. White pawns can never move toward the left. Conversely, black pawns move up and down and right to left. Black pawns can never move right.

Setup

The board consists of 6 individual 6x6 boards laid out left to right, for easier viewing. This represents a 3 dimensional 6x6x6 cube. There are 36 squares in each of the 6 boards. These squares are called Little squares, and the 6 boards are called Big squares. For some pieces, movement from Big square to Big square is the same as their movement from Little square to Little square. For other pieces, the movement through Big squares is different than the standard 2D movement of the piece [notably in bishop analogs].

Pieces

King. Moves 1 square in any direction, including up and down. A king may move to [up to] 10 positions in a turn.

Guard. Moves exactly as the king, but is non-royal.

Minister. A combination piece that moves as warmachine or knight.

High Priestess. A combination piece that moves as elephant or knight.

Warmachine. This piece is a combination of wazir and dabbabah. It steps 1 or leaps 2 squares orthogonally, jumping over any piece next to it. It moves the same on Big squares as it does on Little squares.

Elephant. The elephant is a combination of ferz and alfil, stepping 1 or leaping 2 squares diagonally, from Little square to Little square . It is the diagonal analog of the warmachine, on a 2D plane, that is, within 1 Big square. However, it moves from Big square to Big square orthogonally, stepping 1 or leaping 2 Big squares to end in the same little square 1 or 2 Big squares [2D boards] over. Please see the Notes section for a further discussion.

kNight. The knight in this game is a multipath slider. It does not leap. Instead it slides 1 square orthogonally, the turns 90 degrees and slides 2 more squares, or it slides 2 squares orthogonally, turns 90 degrees, then slides 1 more square. Please see the Notes section for a further discussion.

Pawn. Pawns in this game move and capture as directional 3D wazirs. They have 4 of the 6 possible orthogonal moves. A pawn may not move "backwards". That means it can never move to a Big square closer to the one where its king started the game. Nor may it move closer to its own back rows of Little squares.

Rules

The Held King Rule:

A king may hold the other player's king in one big square. When a player moves the king into the same big square as the opposing player's king, the opposing player's king is "held". The opposing player's king keeps its moves on the little squares, but may not move out of the big square both kings are in.

Only the opposing player's king is held. The player who created the hold may freely move the king out of the big square the enemy king is held in, even to get out of check, or to give a discovered check. This breaks the hold. Otherwise, both kings stay in the same big square until one of them is checkmated.

The held king only needs to be checkmated in the big square it's in, it can't leave. The holding king, to be mated, must have all its allowed big square destinations guarded also.

The formerly held king may immediately follow the other king from the big square, reversing the hold.

Abdul-Rahman Sibahi proposed an extension of the held king rule to occupying the same little squares. If a king can legally move onto the same little square as the opposing king, on any big square anywhere, the opposing king may move freely from big square to big square, but may not move off the little square it is on until the hold is broken. I do not know if this is enough to facilitate mate in the game, but it has to help.

The Held King Rule is more effective the larger the board is. Why larger? Because it’s easier to get onto a particular square, big or little, when there are more of them available. Ideally, you’d play on a board of minimum side 6 or larger. A 4 dimensional 6x6x6x6 with its 1296 positions might be a little unwieldy, but a 6x6x6, with 216 locations, is a nice size on which to try the Held King rule for 3D.

Notes

Diagonal Movement

I do not use diagonal movement between 2D boards, or "Big squares". There are a number of reasons for this, learned from my experiences with 4D design. This cheat, and I acknowledge that in some senses it is a cheat, eliminates all the problems associated with higher than 2D diagonal movements. It also maintains the ratio of the values of the orthogonal and diagonal pieces vis-a-vis 2D values far better than using diagonals in the 3rd [or higher] dimension. It makes defense more manageable, and thus reduces the number of pieces required on the board for a good game.

Look at the moves from the point of view of the piece moving. Each different direction a piece can move is represented by a ray from the piece to the destination point. A wazir or rook, in 2D, can move in 4 directions orthogonally. A ferz or bishop can move in 4 directions diagonally, in 2D. When we move to 3D, the wazir/rook moves "up" and "down" also, for a total of 6 directions. The ferz/bishop gets 8 more directions, for a total of 12. Thus all diagonal pieces become about double in power compared to the orthogonal ones. And the elephants in this game leap. That makes them pretty unstoppable, without some limitations.

the Sliding Knight

The knight in this game does not jump, for the same reasons the elephant moves between Big squares orthogonally instead of diagonally. Its power is greatly amplified by adding dimensions. So making it a slider is a balancing mechanism. This rule I am somewhat concerned about. I may also try allowing the knight its leap within any Big square, but make it a lame 2+1 slider when it moves from one Big square to another one. Note, however, that the knight is the only piece that may change its position on both Big squares and Little squares during the same move/turn with the current set of rules. That makes it rather powerful.

the Neutral Pawn Move

Aka: the "this-is-not-a-backwards-pawn-move”; a blatant attempt to put more defense into the game. One unusual feature of this game is that the pawns are already "passed". It requires both players to deliberately bring the pawns into contact.

Allow the pawns to “drop back” one big square while simultaneously moving forward one little square. For example, on its first move, the king's pawn could move to the little square directly in front of the king, if the king's elephant has moved from that setup square.

This special move takes the place of the FIDE pawn's initial double step. It may only be made on the pawn's first move, and it is non-capturing.