On the beach, scratching marks in the sand with a stick, my 4-year-old son was already good enough to force a draw in noughts and crosses, also known as tic-tac-toe.

In case there is anyone on the planet unfamiliar with this game, it is played on a 3 × 3 grid, with players taking turns to add their symbol – an X or an O – in one of the spaces. The winner is the first to place three of their symbols in a row horizontally, vertically or diagonally.…