How is it different from ordinary tic-tac-toe?

The ordinary rules are here too, but you can also choose vanishing tic-tac-toe, where marks disappear, and a 5×5 version where you line up four.

Is there a sure way to win?

In classic tic-tac-toe, if both players play their best, the game is a draw. A sure win appears only when your opponent makes a mistake in the first few moves. The Advanced CPU plays the classic rules perfectly, so it never loses.

What rules does random match use?

In random match, players who chose the same rules are paired. In a room match, the room creator chooses the rules.

Asobi Lounge / Games / Tic-Tac-Toe

Tic-Tac-Toe rules and how to think about winning

The classic game where players take turns marking O and X, and you win by lining up your marks in a straight line vertically, horizontally or diagonally. Besides the familiar 3×3 rules, you can play "vanishing tic-tac-toe" (消えるまるばつ), where each player has at most three marks and the oldest disappears, and a 5×5 version where you line up four.

Also known as: Noughts and Crosses, Marubatsu
Players: 2 players (1 against the CPU)
Price: free
Runs in the browser (no install)

Play now

The game screen is in Japanese.

Games against the CPU and solo modes work right away without signing in. Online play (random matches and private rooms) and saving stats or leaderboard scores require signing in with a Google account. To play with a friend, your friend also needs to create an account and register as your friend.

Tic-Tac-Toe modes

Random match (ランダムマッチ): play online against someone who chose the same rules
Room match (ルーム対戦): play a friend using a room ID (the room creator chooses the rules)
Play against the CPU (CPU対戦): four levels from Novice to Advanced
Two players (ふたりで対戦): take turns on one screen

Basic rules of Tic-Tac-Toe

The first player is O and the second is X, and you take turns marking empty squares.
Classic tic-tac-toe: on a 3×3 grid, the first to line up three vertically, horizontally or diagonally wins. If the board fills up, it is a draw.
Vanishing tic-tac-toe: each player can have at most three marks. When you place your fourth, your oldest mark disappears. The board never fills up, so if there is no result in 100 moves, it is a draw.
Four in a row on 5×5: on a 5×5 board, the first to line up four wins. If the board fills up, it is a draw.

How to play on Asobi Lounge

Click (tap) the square you want to mark. The square with the last mark turns pale gold.
In vanishing tic-tac-toe, the mark that will disappear next is shown faded. It disappears only after the new mark is placed, so you cannot mark its square yet.
Against the CPU you can use Undo (待った) and up to three Hints (ヒント) per game. If you keep playing, your results are counted.
Start a room match by sharing the room ID or with a friend invite.

Why classic tic-tac-toe ends in a draw

Counting every way a 3×3 game can be played until someone wins or the board fills up, there are 255,168 games: 131,184 won by the first player, 77,904 won by the second player and 46,080 draws (counted by computer with the same rules as this site). The first player wins more of these games, but if both players play their best, the game always ends in a draw.

Example: what the first two moves decide

If the first player marks the center and the second player marks an edge (a square on the border that is not a corner), the first player has a sure way to win. If the second player marks a corner instead, they can hold a draw.
If the first player marks a corner, the only reply that lets the second player draw is X in the center. Any other square gives the first player a sure way to win.
The Advanced CPU has read all of these sequences, so it never loses at classic tic-tac-toe. If you want to win, try Intermediate or below, or one of the other two rule sets.

How the CPU levels differ

Novice: plays almost at random. It sometimes misses your lines.
Beginner: never misses a winning move and usually blocks you.
Intermediate: reads a little ahead. It can be weak against double threats.
Advanced: plays classic tic-tac-toe perfectly and never loses. It also reads deeply in the other rule sets.

Tips

The center square is part of four lines, so it is the place to take first.
Create a double threat that aims at two lines at once, and your opponent can block only one.
In vanishing tic-tac-toe, a line that includes your own mark that vanishes next cannot be relied on. Read ahead to the shape after your opponent's faded mark disappears, and you will see holes in their defense.
Hint shows the move the strongest CPU would choose. Use Undo to go back to a lost position and compare the hint with your move to see where you missed a win.

Frequently asked questions

How is it different from ordinary tic-tac-toe?: The ordinary rules are here too, but you can also choose vanishing tic-tac-toe, where marks disappear, and a 5×5 version where you line up four.
Is there a sure way to win?: In classic tic-tac-toe, if both players play their best, the game is a draw. A sure win appears only when your opponent makes a mistake in the first few moves. The Advanced CPU plays the classic rules perfectly, so it never loses.
What rules does random match use?: In random match, players who chose the same rules are paired. In a room match, the room creator chooses the rules.
Is Tic-Tac-Toe free to play?: Yes, it costs nothing. Games against the CPU and solo modes work right away without signing in. Online play (random matches and private rooms) and saving stats or leaderboard scores require signing in with a Google account. To play with a friend, your friend also needs to create an account and register as your friend.