Have you ever played Tic-tac-toe, the famous simple game that most of us played when they were young? OXO is an online slot game developed by Tom Horn Gaming that is based on this popular game. One of the things that are unique about this game is the black and white visuals. In addition, this game has just 3 reels and 5 paylines. Instead of paying for matching symbols, this game is paying for specific combinations. There’s a special prize too for those who will manage to spin all reels empty. OXO is by far one of the simplest Online Slots we’ve ever seen.