heh, TIC tac toe
One of the first example made with TIC. Kept simple for learning purpose.
The AI is just a move ahead you, so you can beat it.
If you wanto to see under the hood, hit ESC to reach the prompt of a virtual computer. Then use Alt+1 to move to code editor. Alt+2 for the sprite editor and so on. There's a small ester egg right inside the code if you find it you can Run the modified game using Ctrl+R
See more at https://nesbox.itch.io/tic and join the fun.