Ultimate Tic-Tac-Toe takes the classic game of Tic-Tac-Toe and adds an extra layer to it. Each square of the 3×3 game board contains another smaller 3×3 game board. Where you make your move in a square of any small board, you send the opponent in the respective square of the big board. 3 in a row in a small board wins the small board, 3 small boards in a row win the game.
My reason for making the game was to learn more about multiplayer and networking. I ended up writing all the multiplayer server code from scratch in PHP. Not my first choice if I was to do it again, but I learned a lot.