How to Play Relative Chess
The Core Idea
Relative Chess is played like standard chess, but with one twist: when you move a piece, it stays where it is and all the other pieces shift in the opposite direction. The result is relatively the same as a normal chess move, but the board itself moves around.
The Boards
The game is played on two boards:
- The enlarged outer board (dark squares) — a larger grid (default 16×16, configurable) that sets the absolute boundaries of the game.
- The inner conventional board (light/brown squares with gold border) — the standard 8×8 chess board, which shifts around within the outer board as moves are made.
How Movement Works
Click a piece, then click a target square. Instead of the piece moving to that square:
- The piece you selected stays exactly where it is.
- Every other piece on the board shifts in the opposite direction by the same amount.
- The inner board boundary also shifts with the other pieces.
For example, if you tell a knight to move 2 up and 1 right, the knight stays put and everything else moves 2 down and 1 left.
Recentering: Aristotelian vs Leibnizian
Relative Chess has two modes that control whether the inner board drifts freely or stays centred:
- Leibnizian (recentering off) — The game is inspired by the notion of Leibniz shifts, according to which a motion of the entire universe is no motion at all. Thus we may reconceive a piece's movement as the opposite motion of the rest of the universe (i.e. all the other pieces and the inner board). No recentering happens — the inner board drifts freely based on the moves played.
- Aristotelian (recentering on, default) — To make the game more pleasant to play, after each move the board recenters by one square in the vertical and horizontal directions back toward the centre of the outer board. This is inspired by Aristotle's notion of natural motion. All pieces shift along with the recentering.
Captures
Captures work just like normal chess in relative terms. If the square you target contains an enemy piece, that piece is captured (removed from the board).
Death by Edge
When other pieces are shifted, some may be pushed off the edge of the outer board. Any piece that falls off the outer board is immediately captured — regardless of colour. This is called death by edge.
Board Boundary Rule
A move is illegal if it would push the inner 8×8 board past the edge of the outer board. This limits how far pieces can move in any given direction, depending on where the inner board currently sits.
Leave Inner Board Setting
- Yes — Pieces can be pushed outside the inner board onto the outer board. They survive there but risk death by edge on future moves.
- Sides only — Pieces can leave the inner board from the left or right sides, but cannot leave from the top or bottom (such moves are illegal).
- No — Pieces cannot leave the inner board at all (any move that would push a piece outside it is illegal).
Special Moves
- Castling — Works as in standard chess. The king moves 2 squares toward a rook. The rook is repositioned to the other side of the king. Neither piece may have moved, the path must be clear, and the king cannot be in or pass through check.
- En passant — Supported, using relative positions.
- Pawn promotion — When a pawn reaches the back rank of the inner board, a popup lets you choose to promote to a queen, rook, bishop, or knight.
Check, Checkmate & Stalemate
These work exactly as in standard chess, using the relative positions of pieces. The board boundary constraint means some escape moves may be illegal — making checkmate easier near the edges.
AI Opponent
You can play against an AI that plays either Black or White. Three difficulty levels are available (Easy, Medium, Hard), which control how many moves ahead the AI searches.
Chess Clocks
Optional time controls are available: Bullet (1+0), Blitz (3+2), Rapid (10+5), and Classical (30+20). The clock starts when the game begins, switches after each move, and adds the increment to the moving player's time. Running out of time loses the game.
Undo, History & Review
- Undo Last Move — Click the button or press Ctrl+Z (Cmd+Z on Mac) to take back your last move. Against the AI, this undoes both your move and the AI's response.
- History browsing — Press Left/Right arrow keys during a game to step through past moves with animated transitions. Press Escape to return to the live game. The clock pauses while browsing.
- Save & Review — Download the current game as a JSON file, or upload a saved game to replay it move by move.
Controls
- Click a piece to select it (legal moves shown as dots).
- Click a highlighted square to make the move.
- Click a different friendly piece to reselect.
- Click an empty/invalid square to deselect.
Keyboard Shortcuts
- Ctrl/Cmd+Z — Undo last move
- Left Arrow — Step back through move history
- Right Arrow — Step forward through move history
- Escape — Return to live game from history