You assume that you are playing "bumper pool" on a square "pool table". You assume that you begin my shooting the ball upward and to the right from the lower left-hand corner. (This can be drawn on a piece of paper.) The ball bounces off the sides of the table as it would on a perfect pool table.
I will spend most of the time asking, and then answering, the question: Where should you aim so that the ball takes 21 bounces before dropping in the upper left-hand corner pocket?