An implementation of Ultimate Tic Tac Toe with AI to play against. Hosted at https://jhocevar.github.io/ultimateTTT/
The Computer player is implemented using a Monte Carlo Tree Search algorithm that finds the best move by simulating games and building out the game tree.
Because it all runs in the frontend javascript, the number of simulations run is much lower than the Java version I created first, however, it still appears to be pleanty.
The app also allows you to play the AI against itself, or a 'dumb player' who always chooses a move at random and view the games as they play out.