Tic-Tac-Toe
Classic X's and O's — or the Sum 15 variant
How to play
- Choose to play against the computer or with someone else on the same device, and also pick the theme: classic (X and O) or numbers (Sum 15).
- Tap an empty space on the board to mark your turn.
- Take turns with your opponent, one mark at a time.
- Try to form a line of three of your marks — horizontal, vertical, or diagonal — and block your opponent's lines.
- Whoever forms a line of three first wins; if the board fills up and no one does, it's a draw.
Two of your marks already lined up, with the third space in that line free (horizontal, vertical, or diagonal), win the game as soon as you play there — it's worth watching whether your opponent is close to completing theirs too.
About this game
Tic-Tac-Toe is a classic almost everyone already knows, so there's no learning curve to get started — and it still has real strategy: predicting the opponent's move and blocking in time.
Beyond the traditional X and O, DIVILLI also offers the "Sum 15" variant: the same nine spaces get numbers from 1 to 9, and whoever collects three numbers that add up to 15 wins — it's the same game underneath, just dressed differently, and a light way to practice mental math.
Frequently Asked Questions
Is the Sum 15 variant a different game from Tic-Tac-Toe?
No — it's the same game underneath: the numbers are arranged so that forming a line of three is always the same as adding up to 15 (a magic square). Only how the board is shown changes.
Is there a strategy to never lose at Tic-Tac-Toe?
Yes — always playing the best possible response, Tic-Tac-Toe never has to end in a loss, only a win or a draw. It's a good game for thinking a few moves ahead.