The game is actually called "Balls" but is commonly refereed to as the circle game. It is called balls because the original objective of the game was to get someone to look at your balls. To play , you create a circle with your thumb and index finger ( like the ASL sign for the letter F) and you place it somewhere below your waist, preferably closer to your balls. Then you try to get someone to look at the circle. If they look at the circle, you get to say, "Hey man, why are you looking at my balls?" and punch them. But they do have a chance to not get punched. If they can put their finger in the circle and pull it back out before you close the circle on their finger, they don't get punched. If you do catch their finger, you get to say " Hey man, why are you trying to touch my balls?" and you punch them twice.
The game has no time limit and can even be played over the span of your life. kind of like the Slug Bug Game