Create an app for a two player Tic-Tac-Toe game.
At first just get the game working, do not let the computer determine the winner.

You will need to Change Between Two Players

This can be done using 9 buttons or 9 image Sprites. The code is similar, but only use one of the two methods.

use the code tip ButtonsAsParameters to simplify your code OR use the code tip ImageSprites as Parameters to simplify your code.
use the code tip List Processing to simplify your code.

You will need to modify the code you have to include a List of Buttons to simplify your code.

How to determine the winner?  Class discussion.