XO Arena is a new Tic Tac Toe game in which you can play against another person or an AI. It has three levels of difficulty (easy, medium, hard) for the AI. The game allows players to keep track of their scores, switch from one game mode to the next, and play on any device because of responsive design. I learned how to manage the state of the game, accept user input, and create a basic AI using JavaScript logic and the minimax strategy. Overall, it was a lot of hard work, but it was also a great deal of fun, and I was able to gain a better understanding of how actual games are built.