Ultimate Tic-Tac-Toe is an interesting and strategic variation of Tic-Tac-Toe. It consists of a large Tic-Tac-Toe board, where each space contains a small Tic-Tac-Toe board. Your goal is to get three in a row in the large game. To win a space in the large game, you must win the small game in that space.
Here is the catch: when you move in a space on a small board, the other players next move must be in the corresponding space on the large board. For example, if you move in the middle board top-left corner, your opponent's next move must be in the top-left board (see screenshot). If you send your opponent to a board that has already been won, then they get to move wherever they want.