如何玩井字棋

Tic-Tac-Toe is played on a 3x3 grid. Two players take turns placing their marks — X or O — in empty cells.

The goal is simple: be the first to get three of your marks in a row, column, or diagonal. X always moves first.

Players alternate turns. X goes first, then O, then X again, and so on.

Here X has opened in the center, O responded in the top-right corner, and X has taken the top-left corner. Each mark is permanent — once placed it cannot be moved.

A player wins by completing a line of three marks. This example shows X winning with a horizontal line across the top row (cells 0, 1, 2).

There are three possible horizontal wins: the top row, the middle row, and the bottom row.

Lines can also run vertically (down a column) or diagonally (corner to corner).

This example shows O winning with a diagonal from the top-left corner (cell 0) through the center (cell 4) to the bottom-right corner (cell 8). There are two diagonals and three columns that can win.

If all nine cells are filled and neither player has three in a row, the game ends in a draw (also called a "cat's game").

With optimal play from both sides, Tic-Tac-Toe always ends in a draw — making strategy especially important against imperfect opponents.

The center cell is the most valuable square on the board. It is part of four possible winning lines (both diagonals, the middle row, and the middle column) — more than any other cell.

Corner cells come next (each belongs to three winning lines), while edge cells are weakest (only two lines each). Opening in the center gives X the best chance to create a fork — a position that threatens two winning lines at once.

Ultimate Tic-Tac-Toe is played on 9 sub-boards arranged in a 3×3 grid. Each sub-board is a standard 3×3 Tic-Tac-Toe game.

Your cell choice determines which sub-board your opponent must play in next. For example, if you play in cell 4 (center) of any sub-board, your opponent must play in sub-board 4 (center). Win three sub-boards in a row to win the game!