Tournament ruleset
Ultimate Tic-Tac-Toe, played properly
The exact ruleset the Grid Gambit server enforces - every forced move, every closed-board edge case, every time forfeit. It's also everything you need to run your own offline tournament: read the rules, scroll down, start the ten-minute per-player clock.
10-minute per-player countdown
Chess-clock style. Each player has ten minutes total. Tap your clock after every move. If your clock hits zero, your opponent wins on time.
1. Overview
Ultimate Tic-Tac-Toe is played on a 3×3 grid of 3×3 tic-tac-toe boards. Each small board is a local board; the full arrangement of nine local boards is the global board. Two players, X and O, alternate turns. X plays first.
2. Objective
Win the game by claiming three local boards in a row on the global board - horizontally, vertically, or diagonally. A local board is claimed by winning that board in normal tic-tac-toe.
3. Starting the Game
The first player may place their mark in any empty cell on any local board.
4. Forced Board Rule
After the first move, the cell position just played determines which local board the opponent must play in next. If a player marks the center cell of their current local board, the opponent must play in the center local board of the global board. Mark the bottom-right cell and the opponent is sent to the bottom-right local board. This rule applies on every turn unless the target board is closed.
5. Winning a Local Board
A player wins a local board by making three in a row within that local board - horizontal, vertical, or diagonal. Once a local board is won, it is immediately claimed, closed, and no further moves may be played in it. Tournament directors should mark won local boards clearly for X or O.
6. Drawn Local Boards
A local board that becomes full without either player making three in a row is a drawn local board. It is closed and claimed by neither player. Drawn local boards do not count for either player on the global board.
7. Closed Board Rule
A local board is closed if it is already won or completely full. If a player is sent to a closed local board, that player gets a free move: they may play any empty cell on any open local board.
8. End of Game
The game ends immediately when a player claims three local boards in a row on the global board. If all local boards are closed and neither player has made a global three-in-a-row, the game is a draw.
9. Clock and Time Forfeit
Each player receives a ten-minute countdown at the start of the match. The clock of the player to move runs during their thinking time and is stopped by completing a legal move. A player whose clock reaches zero forfeits the game on time, unless the opposing side has insufficient material to win - in Ultimate Tic-Tac-Toe that exception never applies, so a flagged player always loses.
Examples
- Forced board. X starts by playing the top-left board, center cell. O must now play in the center local board.
- Free move from a closed board. O plays a cell that sends X to the top-right local board. That board is already won. X may play any empty cell on any open local board.
- Double win. O completes a line inside a local board, claiming it. That board is O's third in a row on the global board - O wins the match immediately.
- Closed draw. The last open local board fills without a line. No player has three claimed local boards in a row. The game is a draw.
Edge Cases and Rulings
- Can a player choose any board after the first move?
- No. A player must play in the local board indicated by the opponent's previous cell, unless the target board is closed.
- Can moves still be played inside a won local board?
- No. Under tournament rules, won local boards close immediately.
- Does a drawn local board count toward the global line?
- No. It belongs to neither player.
- If nobody gets three in a row, does the player with more local boards win?
- No. The result is a draw unless a player completes a global three-in-a-row.
Quick Reference
- First move: anywhere.
- Later moves: follow the send rule.
- Won local board: claimed and closed.
- Full unwon local board: drawn and closed.
- Sent to a closed board: play anywhere legal.
- Win condition: three claimed local boards in a row.
- No global line when all boards close: draw.
- Clock hits zero: time forfeit.