Check an extension of this version that allows you to play against the computer: https://codepen.io/alvaromontoro/pen/BexWOw. And all in CSS!
Visit a collection of other CSS games that I have developed.
This is SO clever! The original developers of CSS would NEVER have dreamed that one day someone would be able to play a fully functional tic tac toe match using it.
Pure Brilliance! that's it!
Need to know how to enable it? Go here.