You have been challenged, or maybe you challenged someone to play racquetball.
To serve, press the red button. You got to move the player to the place where the shadow of the ball at about the level of your feet. Rackets will automatically swing. When you serve, the ball must hit the front wall before it hits the floor. Then your opponent can hit the ball before it hits the floor, or it can let it bounce, but you can jump only once. He can not jump twice. You serve each time, until you miss. If you serve and your opponent misses, you get one point. You can only get points on rounds, where you serve. The first player in the twenty-one points wins.