❌⭕ Tic-Tac-Toe

Tic-tac-toe has been completely analysed: if both players play correctly, every single game ends in a draw. There is no clever opening that wins against someone who knows what they are doing.

That sounds like it ruins the game, and for two experts it does. But it makes tic-tac-toe an unusually clear lesson in what strategy actually is — you cannot win by playing well, you can only win when your opponent errs, so the real skill is spotting the error and punishing it.

A fork is a move that creates two winning threats at once. Your opponent can only block one, so the other wins on your next turn. Every tic-tac-toe victory between competent players comes from a fork.

The classic setup is taking a corner, then a second corner on the same side once your opponent has answered in the centre. Two corners plus an open edge between them often gives two lines at once. Learning to see forks two moves out is genuinely transferable — it is the same pattern as a double threat in checkers or connect four.

The CPU follows a simple priority list: take a winning move if one exists, block your winning move if one exists, otherwise take the centre, otherwise a random corner, otherwise anything.

That makes it solid but not perfect. It will never miss an immediate win or an immediate block, so careless play loses. It also does not look further ahead than one move, which means a well-built fork beats it — a good target if you want to prove you have understood the idea.

For a five-year-old, tic-tac-toe is the first game where thinking ahead visibly beats not thinking ahead. It introduces the idea that your opponent has intentions, that a move can do two jobs at once, and that some positions are lost before the last piece is played.

Pass-and-play mode is on the same screen, so it works as a two-player game on one phone. When it stops being a challenge, Connect Four at cerdikcerdik.com/games/connect-four is the natural next step — same idea of lines and threats, on a board large enough that nobody has memorised it.