Six-Tac-Toe is played on a 4x6 square grid. One player writes an "X" in a square and the other player then chooses whether to make the odd or even moves.
On a move a player can write either an "X" or an "O" in a square. If they create one or more "tic-tac-toes" - three matching symbols in a line - they must mark them. However, lines of more than three symbols don't count, and a line of three that could be extended is not marked.
Once all the squares are filled the player making the even moves wins if there are at least six tic-tac-toes marked. Otherwise the odd player wins.