Play 4-Dimensional Tic Tac Toe here. 4-Dimensional Tic-Tac-Toe takes longer to play than ordinary tictactoe and is much more challenging. Tic tac toe is also known as noughts and crosses or Xs and Os. The game on this site is called tictactoe because it is based on a grid of 3x3 squares. Some games use a 4x4 matrix instead. To play noughts and crosses in three dimensions, make three tic-tac-toe grids and call them Upper Middle and Lower. There will be 27 squares, but the middle square will provide too much benefit. So on this site on both 3-D O's and X's and 4D Tic Tac Toe the middle square is unavailable to either player. In Four dimensional Xs and Os there are 81 squares cut down to 80 as the middle square is unavailable. Playing 4-D tic-tac-toe can help to exercise your pattern recognition and short term memory skills. The activity of thinking ahead and pattern recognition tasks can help train your brain and helps to counteract the ageing process or improve learning.