Complete Official Rules
The formal and complete ruleset of Void Chess, intended as a definitive reference.
Article 1 — The Board and Starting Position
1.1. Void Chess is played on a square board of 81 squares arranged in a 9-column by 9-row grid. Columns are labelled a through i from left to right. Rows are numbered 1 through 9 from White's side.
1.2. The board is oriented so that each player has a light-coloured square in the near-right corner.
1.3. At the start of the game, every square on the board is in the Normal state. There are no unstable tiles or void tiles.
1.4. Each player begins with 16 pieces: 1 King, 1 Queen, 1 Minister, 2 Rooks, 2 Knights, 2 Bishops, and 9 Pawns.
1.5. White's back rank (row 1), from a1 to i1, is arranged as: Rook, Knight, Bishop, Queen, King, Bishop, Minister, Knight, Rook. White's 9 Pawns occupy the entirety of row 2.
1.6. Black's back rank (row 9), from a9 to i9, mirrors White's arrangement. Black's 9 Pawns occupy the entirety of row 8.
1.7. White makes the first move. Players alternate turns thereafter. A player must make exactly one move per turn; passing is not permitted.
Article 2 — Tile States
2.1. Each square on the board exists in one of three states: Normal, Unstable, or Void.
2.2. Normal tiles function as ordinary chess squares. Any piece may occupy or move through a normal tile, subject to standard movement rules.
2.3. Unstable tiles are created when a capture occurs (see Article 5). An unstable tile is visually marked in red. Pieces may occupy and move through unstable tiles, but any piece remaining on an unstable tile at the end of that piece's team's turn is subject to destruction by the Void Janitor (see Article 6), with the sole exception of the Minister.
2.4. Void tiles are permanent gaps in the board. No piece may move to, move through, or occupy a void tile, with the sole exception of the Minister. Void tiles are impassable barriers for all movement and attack calculations.
2.5. When a piece leaves an unstable tile (moves away from it), that tile immediately becomes a void tile.
Article 3 — Movement of Standard Pieces
All standard chess pieces move according to orthodox chess rules, with the additional constraint that void tiles are impassable.
3.1. King — Moves exactly one square in any direction (horizontally, vertically, or diagonally). The King may not move to a square that is attacked by an opponent's piece, that is a void tile, or that would result in the King being in check.
3.2. Queen — Moves any number of squares in a straight line horizontally, vertically, or diagonally. The Queen may not pass through or land on void tiles, and may not pass through occupied squares.
3.3. Rook — Moves any number of squares in a straight line horizontally or vertically. The Rook may not pass through or land on void tiles, and may not pass through occupied squares.
3.4. Bishop — Moves any number of squares in a straight line diagonally. The Bishop may not pass through or land on void tiles, and may not pass through occupied squares.
3.5. Knight — Moves in an L-shape: two squares in one direction and one square perpendicular, or one square in one direction and two squares perpendicular. The Knight may jump over occupied squares and void tiles, but may not land on a void tile or a square occupied by a friendly piece.
3.6. Pawn — Moves one square forward toward the opponent's back rank. From its starting position, a Pawn may optionally move two squares forward in a single move, provided both squares are empty and not void. A Pawn may not move forward onto a void tile. Pawns capture one square diagonally forward. Pawns may not capture onto a void tile.
Article 4 — The Minister
4.1. The Minister is a new piece unique to Void Chess. It begins the game on g1 (White) and g9 (Black), between the second Bishop and the second Knight.
4.2. Movement. The Minister moves in a two-step sequence within a single turn:
- Step 1: The Minister moves exactly one square in any of the eight directions (horizontally, vertically, or diagonally). The destination square must be either empty or occupied by an enemy piece (a capture). The destination square may be a void tile or an unstable tile.
- Step 2 (conditional): If and only if Step 1 landed on an empty square (no capture was made), the Minister may then move one additional square in any of the eight directions. The Minister may change direction between Step 1 and Step 2. The Step 2 destination may not be the Minister's original square (the square it occupied before Step 1). Step 2 is optional; the Minister may choose to stop after Step 1.
4.3. If the Minister captures an enemy piece on Step 1, the move ends immediately. There is no Step 2.
4.4. On Step 2, the Minister may land on an empty square or capture an enemy piece.
4.5. On an open board with no obstructions, the Minister can reach up to 24 distinct squares from its position (all squares within a 5x5 area centred on the Minister, excluding its own square).
4.6. Healing. When the Minister moves onto an unstable tile or a void tile, that tile is immediately restored to Normal state. The Minister is the only piece that may move onto void tiles.
4.7. Void Immunity. The Minister is immune to the Void Janitor. The Minister is never destroyed by remaining on an unstable tile.
4.8. Blocking. The Minister requires at least one adjacent square (Step 1 destination) to be either empty or occupied by an enemy piece. If all eight adjacent squares are occupied by friendly pieces, the Minister has no legal moves.
Article 5 — Captures and the Creation of Unstable Tiles
5.1. When any piece captures an opponent's piece, the square on which the capture took place becomes an unstable tile. If the square was already unstable (due to a previous capture on the same square), it remains unstable. If the square is a void tile, it remains void — this situation can only arise with the Minister, as it is the only piece that can occupy a void tile.
5.2. If the Minister makes the capture, the tile is healed to Normal state instead of becoming unstable (see Article 4.6). The healing effect overrides the unstable creation.
5.3. En passant captures create an unstable tile on the square where the capturing pawn lands (the en passant target square), following standard capture rules. The captured pawn is removed from its square.
5.4. The piece that just made the capture is safe on the unstable tile for that turn. It will not be destroyed immediately. See Article 6 for what happens next.
Article 6 — The Void Janitor
6.1. The Void Janitor is an automatic process that executes at the end of every turn, after the moving player's piece has completed its move and all tile state changes from that move have been applied.
6.2. The Void Janitor examines every unstable tile on the board and applies the following rules:
- 6.2.1. Safe square exemption: The square that the moving piece just arrived on is exempt from the Void Janitor for this turn. The piece that just moved is always safe, regardless of whether it is on an unstable tile.
- 6.2.2. Friendly pieces on unstable tiles: Any piece belonging to the team that just moved that is currently sitting on an unstable tile (other than the safe square) is destroyed. The piece is removed from the board and that tile becomes a void tile. The Minister is exempt and is never destroyed (see Article 4.7).
- 6.2.3. Opponent's pieces: The Void Janitor does not affect the opponent's pieces. Only pieces belonging to the team that just moved are subject to destruction.
6.3. The Void Janitor may destroy multiple pieces in a single execution if multiple friendly pieces are on different unstable tiles.
6.4. If the King is destroyed by the Void Janitor, that player loses the game (see Article 9.2).
Article 6A — The Life Cycle of an Unstable Tile
The following describes the complete sequence of events from capture to void creation.
6A.1. Creation. A capture occurs on a square. That square becomes unstable. The capturing piece sits on it, safe for this turn (safe square exemption).
6A.2. Escaping. If, on a subsequent turn, the piece on the unstable tile moves away to a different square, the unstable tile immediately becomes a void tile. The piece survives. This happens at the moment the piece leaves, before any other processing.
6A.3. Destruction. If the piece does not move away — that is, the player moves a different piece instead — the Void Janitor will destroy the piece at the end of that turn (because it is a friendly piece still sitting on an unstable tile and it is not on the safe square). The piece is removed from the board and the tile becomes a void tile.
6A.4. Opponent's turn in between. After the capture, the opponent takes their turn. During the opponent's turn, the Void Janitor only affects the opponent's own pieces. The capturing piece (belonging to the other team) is not affected. The piece remains alive on the unstable tile through the opponent's turn. It is only at risk when its own team moves again.
6A.5. Recaptures on the same tile. If the opponent recaptures on the same unstable tile (capturing the piece sitting there), the tile remains unstable because a new capture has occurred on it. The opponent's piece is now sitting on the unstable tile, safe for this turn. The cycle restarts — the new piece must escape or be destroyed on a future turn. As long as captures keep happening on the same square, it stays unstable and never becomes void. The tile only becomes void when a piece finally leaves it or is destroyed on it.
6A.6. Summary. The complete sequence is: Capture → Tile becomes Unstable → Piece is safe this turn → On a future turn, piece escapes (tile becomes Void, piece lives) or piece stays and is destroyed (tile becomes Void, piece dies). Recaptures on the same tile reset this cycle.
Article 6B — Example: Capture, Escape, and Destruction
White's Rook captures Black's Knight on square e5.
| Move | What happens | Tile e5 state | White Rook status |
|---|
| Move 1 (White) |
White Rook captures Black Knight on e5. |
Becomes Unstable |
On e5 — safe this turn (just moved here) |
| Move 2 (Black) |
Black makes any move (not a recapture on e5). |
Still Unstable |
On e5 — still alive (janitor only affects Black's pieces on Black's turn) |
| Move 3 is White's turn. White must decide: |
Option A: White moves the Rook away from e5
| Result: The Rook moves to a safe square. The moment it leaves, e5 immediately becomes a Void tile. The Rook survives. |
Option B: White moves a different piece
| Result: The Rook is still on unstable e5 and is not on the safe square. The Void Janitor destroys the Rook. Tile e5 becomes a Void tile. The Rook is lost. |
White must weigh the value of saving the Rook against the value of making a different move. Sometimes sacrificing a piece to the void is the right strategic choice.
Article 6C — Example: Recaptures on the Same Tile
Repeated captures on the same square keep it unstable and delay void creation.
| Move | What happens | Tile e5 state | Piece on e5 |
|---|
| Move 1 (White) |
White Rook captures Black Knight on e5. |
Becomes Unstable |
White Rook (safe this turn) |
| Move 2 (Black) |
Black Bishop recaptures White Rook on e5. |
Stays Unstable (new capture resets the cycle) |
Black Bishop (safe this turn) |
| Move 3 (White) |
White Queen recaptures Black Bishop on e5. |
Stays Unstable (another capture resets again) |
White Queen (safe this turn) |
| Move 4 (Black) |
Black has no more pieces to recapture. Black makes a different move. |
Still Unstable |
White Queen (still alive — janitor doesn't affect White's pieces on Black's turn) |
| Move 5 (White) |
White moves the Queen away from e5. |
Becomes Void |
Queen survives on its new square |
Throughout three consecutive captures on e5, the tile remained unstable and never became void. The void was only created when the last piece finally left. If White had moved a different piece on Move 5 instead, the Queen would have been destroyed and e5 would have become void at that point.
Article 7 — Special Rules for the King
7.1. Check. A King is in check when it is attacked by one or more of the opponent's pieces. A player whose King is in check must resolve the check on that turn by moving the King, blocking the attack, or capturing the attacking piece.
7.2. King on an unstable tile. If a player's King is on an unstable tile at the start of that player's turn, the player must move the King. No other piece may be moved. The King must move to a legal square that removes it from the unstable tile.
7.3. If the King is on an unstable tile and has no legal move to escape, the King will be destroyed by the Void Janitor at the end of the turn, resulting in a loss for that player.
7.4. The King may not move onto a void tile.
Article 8 — Castling, En Passant, and Pawn Promotion
8.1. Castling. Castling is permitted under the following conditions, consistent with standard chess rules adapted for the 9x9 board:
- The King and the involved Rook must not have previously moved.
- All squares between the King and the Rook must be empty and must not be void tiles.
- The King must not currently be in check.
- The King must not pass through or land on a square that is attacked by an opponent's piece.
- The King moves two squares toward the Rook. The Rook moves to the square the King passed through.
Rooks are positioned at columns a and i. Kingside castling moves the King from e to g; queenside castling moves the King from e to c.
8.2. En passant. En passant capture is permitted under standard chess rules. When a Pawn advances two squares from its starting position and lands beside an opponent's Pawn, the opponent may capture it as if it had moved only one square. This capture must be made on the immediately following turn or the right is lost.
8.3. Pawn promotion. When a Pawn reaches the opponent's back rank (row 9 for White, row 1 for Black), it must be promoted. The player chooses one of the following piece types: Queen, Rook, Bishop, Knight, or Minister. Promotion to King is not permitted.
Article 9 — End of the Game
9.1. Checkmate. If a player's King is in check and that player has no legal move to remove the check, the game ends. The player whose King is checkmated loses. The opponent wins.
9.2. King destroyed by void. If a player's King is destroyed by the Void Janitor (because it was on an unstable tile and could not or did not move away), the game ends. That player loses. The opponent wins.
9.3. King trapped by void. If a player's King is not in check, but every legal move available to that player would result in the King being exposed to destruction by the Void Janitor (after simulating the move and the subsequent janitor execution, the King would be attacked), the game ends. That player loses. The opponent wins. This is distinct from stalemate because the player does have pseudo-legal moves, but all of them lead to the King's destruction via the void system.
9.4. Stalemate. If a player's King is not in check and the player has no legal move whatsoever (not caused by void trapping as described in 9.3, but by a genuine absence of any possible move), the game is a draw.
9.5. Threefold repetition. If the same board position occurs three times with the same player to move, the same castling rights, the same en passant possibilities, and the same tile states, the game is a draw.
9.6. Thirty-move rule. If 30 consecutive full moves (60 half-moves) are completed by both players without any pawn move or any capture, the game is a draw. This is reduced from the standard 50-move rule because the board contracts due to void tiles, and stagnant positions are reached more quickly.
9.7. Insufficient material. If only the two Kings remain on the board and no other pieces exist, the game is a draw. No sequence of legal moves can produce checkmate.
9.8. Void Fortress. If a King is completely enclosed within a region bounded by void tiles (determined by an eight-directional flood fill from the King's position), and all of the following conditions are met, the game is an immediate draw:
- No opponent piece exists within the enclosed region.
- No opponent piece can legally move into the enclosed region.
- No Minister of either colour exists anywhere on the board.
- No Pawn of either colour has a void-free path to its promotion rank (meaning no Pawn can potentially promote to a Minister that could break the fortress).
This rule prevents indefinite games where a King is permanently isolated by voids and no progress is possible.
Article 10 — Move Legality and the Void Janitor Simulation
10.1. A move is legal if and only if, after the move is executed and the Void Janitor is simulated, the moving player's King is not in check and has not been destroyed.
10.2. The game enforces move legality by simulating each candidate move, including all resulting tile state changes and Void Janitor effects, before determining whether the King is safe. Moves that leave the King in check or exposed to destruction after janitor execution are illegal and cannot be played.
10.3. When computing whether a square is attacked (for check, castling, and king safety), the opponent's pseudo-legal moves are used. Void tiles block sliding pieces and prevent Knight landings, as described in Article 3.
Article 11 — Notation
11.1. Void Chess uses standard algebraic notation extended for the 9x9 board. Files are a through i; ranks are 1 through 9.
11.2. Piece letters are: K (King), Q (Queen), R (Rook), B (Bishop), N (Knight), M (Minister). Pawn moves omit the piece letter.
11.3. Captures are denoted with x. Check is denoted with +. Checkmate is denoted with #. Castling kingside is O-O; castling queenside is O-O-O.
11.4. Pawn promotion is written as the move followed by = and the piece letter, e.g. e9=M for promotion to Minister.
