NEGAMAX

Tic-tac-toe against a perfect search

Play X against a search that looks at every possible future board. Turn on its thinking to see the score it gives each open square before it moves.

CONTROLS

◀ ▲ ▼ ▶: Move the cursor (or click a square)
A Z Enter: Place your mark
B X: Show or hide the AI's thinking
START N: New game
SELECT M: Change opponent

OPPONENT

Searches every future board. It cannot lose.

Show the AI's thinking

THIS SESSION

X (you): 0
draws: 0
cpu: 0

All time in this browser: 0 games · X 0% · draw 0% · O 0%

RECENT GAMES

Finished games are recorded here.

HOW THE SEARCH DECIDES

Negamax walks the whole game tree from the current position. A finished game scores 10 minus the number of moves it took, positive for the side that won, so the AI prefers quick wins and drawn-out losses. Tic-tac-toe is small enough to search completely (549,946 nodes in the full tree), so it never needs a heuristic, and with perfect play from both sides every game is a draw.