Tic-Tac-Toe
The classic. Three in a row wins.
X's turn
How to play
Tic-tac-toe is probably the first strategy game you ever learned. Two players take turns putting their mark in an empty square of a 3×3 grid, and X always goes first. Get three in a row — across, down, or corner to corner — and you win. If the board fills up and nobody has three in a row, it's a draw.
If neither player makes a mistake, the game always ends in a draw. That's why it stops being fun once you've figured it out. But people make mistakes, and the quickest win only takes five moves. All it needs is for the other player to miss a block.