A billiard ball game written in java. This is inspired by the game I played when i was in high school. I was curious about the ball trajectories as the momentum equation can only solve the collision of two balls. After i learning the partial form of the momentum equation and angular momentum equation, the mechanism came into my head. Afterwards, i program this game to dispell my doubts. Furthermore, i shared this program for the guys who also have the same doubts. Contact me (sgy-421205643@163.com) if any question.