A nd game (or nk game) is a generalization of the combinatorial game tic-tac-toe to higher dimensions.[1][2][3] It is a game played on a nd hypercube with 2 players.[1][2][4][5] If one player creates a line of length n of their symbol (X or O) they win the game. However, if all nd spaces are filled then the game is a draw.[4] Tic-tac-toe is the game where n equals 3 and d equals 2 (3, 2).[4] Qubic is the (4, 3) game.[4] The (n > 0, 0) or (1, 1) games are trivially won by the first player as there is only one space (n0 = 1 and 11 = 1). A game with d = 1 and n > 1 cannot be won if both players are playing well as an opponent's piece will block the one-dimensional line.[5]