Racquetball is a racquet sport played with a hollow rubber ball in an indoor or outdoor court. Joe Sobek is credited with inventing racquetball in 1950, adding a stringed racquet to the game to increase velocity and control. Unlike most racquet sports, such as tennis and badminton, there is no net to hit the ball over, and unlike squash no tin to hit the ball above. Also, the court’s walls, floor, and ceiling are legal playing surfaces, with only the upper part of the back wall (above 12 feet) being out-of-bounds. Matches are typically best of 3 game series, with the first 2 games to 15 and the 3rd game to 11.