Tic-tac-toe
Nine little squares. One more good idea.
Your round saves in this browser.
X always opens. Choose O to let the computer begin, or share Two players with X first. Tap an empty square; arrows choose a square, Enter or Space marks it, and 1–9 uses reading order. U/R undo/redo and P pauses. Fresh round. Fresh computer wins: 0.
Your achievements 0 / 8
How to play Tic-tac-toe
Place X and O in the nine squares, taking turns. The first player to put three of their marks in a horizontal, vertical or diagonal line wins. A full board with no winning line is a draw. A winning ninth mark counts as a win before a draw is considered. Occupied squares cannot be changed.
X opens every new round
Choose X · first to open against the computer, or O · second to let the computer place X first. X always opens, including after New or Restart; the starting mark does not alternate automatically. In Two players, share the screen with X first and O second. Difficulty and side controls apply only to computer games.
Three computer choices
Easy picks a legal square at random. Normal takes an immediate win, otherwise blocks an immediate opposing win when one exists, then chooses among legal squares. Perfect searches the complete game tree with memoized results. From a fresh board it cannot be beaten: careful play can earn a draw. If loaded into a position that is already a forced loss, it still chooses the best available response rather than pretending the position is safe.
The computer waits briefly and works in scheduled slices. You cannot place another mark during its turn, while New, Undo and Pause remain available when applicable. Cancelled or outdated replies cannot change a replaced, paused, undone or completed round.
Simple controls and useful Undo
Tap or click an empty square. Use arrows to choose an available square; Home and End move across its row. Enter or Space places a mark, and 1–9 selects squares in reading order. U undoes, R redoes and P pauses. Full screen keeps the board and controls together; Back or Escape restores the page.
Against the computer, Undo removes your last decision and its computer reply if the reply has arrived. An immediate human winning mark or a still-pending reply removes only that human mark. The computer's automatic opening cannot be undone by itself. Local two-player Undo removes one mark. Redo restores the exact saved marks, without asking the computer to change an already saved reply.
Saved rounds, practice and first results
Your round, settings, legal move journal, Undo/Redo, active time and achievements save in this browser when storage is available. The clock starts on the first actual mark, pauses in dialogs or when you leave the tab, and waits for Resume on a saved unfinished round. Pause hides the board and cancels pending computer work. Sound starts off, reduced motion is respected and a visible warning explains when saving is unavailable.
Undo and Restart mark the same attempt as practice. Restart clears the board but preserves its first outcome and assistance. Undoing a loss and later winning cannot replace that original loss. New creates a fresh attempt. Reviewing, redoing, restarting and reloading do not duplicate a result or create extra challenge wins.
Eight small achievements
Earn stars for a first mark, taking the center, winning a first-result computer round, beating Normal without Undo or Restart, drawing against Perfect without Undo or Restart, winning a fresh computer round in three of your marks, winning as O without Undo or Restart, and three different unassisted computer wins. A draw against Perfect is a meaningful result; there is no impossible achievement requiring a win against it. Local two-player games can earn the opening milestones and retain their own first results, while computer challenges require actual computer rounds. Celebrations stay below the board.