U3L3-Tic-Tac-Toe

11-8-21: Ideas for improvement

1. Click on a square that has already been selected, do not change costumes.
2. Add some color, costumes
3. Detect wins and losses
4. Create a computer player

11-17: Fix bug so that you cannot play in a square that has already been played.

11-19: Added functions to detect wins and ties, and a variable to stop the game.

Look for repetitive code, and find applications for abstraction.