⭕Play Tic Tac Toe

Tic Tac Toe is famously a solved game: with perfect play from both sides, every single match is a draw. That sounds like it should make it boring, and against the Hard opponent here it very nearly does — the computer searches the entire game tree with minimax and simply cannot be beaten.

That makes it a useful game rather than a trivial one. Hard mode is a puzzle with a fixed answer: can you find the line that holds the draw every time? Easy mode plays loosely, which turns the game into practice at spotting forks — positions where you threaten two lines at once and your opponent can only block one.

Under the hood the computer evaluates every reachable position and prefers faster wins and slower losses, which is why it will take an immediate win rather than dragging the game out. There is no randomness in Hard mode at all.

Three hundred and sixty-two thousand eight hundred possible move sequences, twenty-six thousand eight hundred and thirty distinct games, and every one of them ends in a draw when nobody errs. That is the whole appeal.