| Click or tap | Place your mark on any empty square. |
| Start | Clear the board and begin a new round. |
| Mode | Switch between playing the computer and passing the device to a friend. |
Tic Tac Toe fits on a napkin and has been played that way for a very long time. Two players alternate placing their mark on a three by three grid, and the first to line up three in a row wins. It is the first strategy game most people ever learn, usually somewhere around age five, and it is still a perfectly good way to fill two minutes.
It is also one of the few games that has been completely solved. With correct play from both sides the result is always a draw, which sounds like a flaw until you realise that is exactly what makes it useful. Every loss is a mistake you can identify, which is why the game is a standard teaching tool for the idea of a forced win.
Take the centre if it is available. The centre square sits on four of the eight possible lines, more than any other cell, and holding it doubles the number of threats you can build. If you move first and take the centre, you can never be forced to lose.
When you cannot have the centre, take a corner rather than an edge. Corners belong to three lines each; edges belong to only two. Against an opponent who opened in the centre, a corner reply is the reliable way to hold the draw.
The winning idea in this game is the fork: a single move that creates two separate threats at once. Your opponent can only block one of them. Look for placements that complete two partial lines simultaneously, and equally, watch for the moment your opponent is one move away from setting one up.
Blocking is not optional. Before every move, check whether your opponent has two in a row anywhere with the third square open. If they do, that square is your move, whatever else you had planned. Most losses at this game are not clever traps, they are simply not looking.
Yes. Switch to two-player mode and take turns on the same device, one of you as X and the other as O.
It plays solidly and will punish an obvious mistake. Against correct play from you the game should end in a draw, which is the theoretically correct result.
X moves first, which is a genuine advantage. Alternate who takes X between rounds to keep things even.
Because the game is solved. On a three by three board there is not enough space for either side to create a winning threat if the other side defends properly.
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