Ultimate tic-tac-toe

Ultimate Tic-Tac-Toe is a complex variant of the traditional game of Tic-Tac-Toe. Here's how it works: ### Setup: - The game is played on a 3x3 grid, but instead of just marking Xs and Os, each cell of this grid contains its own 3x3 Tic-Tac-Toe board. - Thus, the overall game consists of 9 smaller Tic-Tac-Toe boards (one for each cell of the large grid).