Abstract: A layout which is practically useful for playing tic-tac-toe (TTT) in four dimensions is disclosed. The layout consists of an array of tiles, each tile containing a 5×5 array of substantially square cells, where the tiles are arrayed in a 5×5 pattern. For ease of visual interpretation, the tiles are preferably separated by approximately the width of a cell. The layout is implemented physically or as an electronic program coupled to a display. The rules are analogous to classical TTT; two variants are described.