Tic-Tac-Toe

Tic-Tac-Toe (Noughts and Crosses in Britain) is a simple two-player game played on a 3×3 grid. Players alternately place an X or O in an empty cell; the first player to make three in a row horizontally, vertically or diagonally wins. Solved by trivial game-theory: perfect play by both sides always ends in a draw. Its ancient ancestor Terni Lapilli was played in Roman street-tables 2,000 years ago. The universal 'first strategy game' for children worldwide.