Circu.io is one of the simplest io games that you can understand how to complete your task as soon as you see the instruction at the starting screen. The mission is to be the first player who dominates the top spot on the leaderboard. What you need to implement is pretty easy. When the tiny red circle exists on the playing field, you have to move the mouse cursor and click on it quickly in order to make that item disappear. It is also the most important key that allows you to win the challenge. From that result, you can earn the next level and rank up. In Circu.io, you will have the chance to compete against plenty of other opponents. Do not let them overtake you! In case you act too slow, the object will become larger and make you lose. Obviously, the difficulty does not stop that. Get ready to check your eyes and your hand right now! Good luck!