In 1993, Kevin Crowley and Robert S. Siegler devised a strategy for playing a perfect game of Tic Tac Toe. This project is a JavaScript implementation of that strategy. You can play—and try to beat it—in this nice web interface.
Note: This game uses many modern technologies, such as calc and viewport units in CSS and classList in JavaScript. Therefore, you should run it in a modern browser that supports CSS3 and ES5. Unless, you don’t want to play. In which case, feel free to use IE6 😊