4d tic tac toe is an extension of the standard 2 dimensional tic tac toe. The game differs in that the playing field extends to four dimensions rather than two, and the game keeps going until no one can move, the winner being determined by the number of rows each player has.

The following diagram shows how the four dimensional playing space is represented on a two dimensional page.

Represented as vectors , the point a is <1,1,1,1>, while the point b is <1,1,3,2>.

It is a bit hard to see all the rows. To help you the following diagram shows all the rows containing the point <1,1,1,1>.