That was really fun! Spent quite some time playing, it's such a chill game! The animations and minimal design work really well with it. AI difficulty curve seems to be done really well too. Never played this rendition of tic-tac-toe so it was cool to see it.
If you'd like feedback, here are two tiny things :)
A restart button might be helpful especially when you know you made a wrong move. The wall of text for instructions is a bit overwhelming -I'll be honest I didn't read it (learned through trial and error). Little bite-size instructions to click through might work well.
If I still commuted, I would definitely be playing this on the train haha Great work all around!