With BallStrike and a front-facing PC camera--a camera facing you--stand seven feet (two meters) from the camera, and BallStrike will put balls of different colors in your room. Move around to destroy the balls, and destroy as many as you can within the alloted time. Some balls reward you with more points than others; you get some points for destroying red balls, more for destroying blue balls, and even more for destroying green balls. Avoid black balls: those are bombs. As you are moving your body to take out red, green, and blue balls while avoiding black balls, you are exercising. A calorie counter estimates how many calories you have burned.