Ponder This Challenge - October 2026 - The Ultimate Ultimate Tic-Tac-Toe Game

The well-known game of Ultimate Tic-Tac-Toe is played on a 9×99\times 9 board (with the rows and columns numbered by 0,1,…,80,1,\ldots,8), conceptually divided into nine 3×33\times 3 small boards. The players are denoted by "X" and "O" and take turns, starting with X.