The RoboGyro Light Ball is really one of the neatest new items we have seen in a long time. The ball has an inner unit that gyrates and rotates 360 degrees. In your hand, this means the super-bright green and blue LEDs form wild spinning light patterns in every direction as the inner unit rotates in the ball (don't worry, the ball will stay still when cupped in your hand). Set the ball on the ground though, and it becomes like one of those robotic vacuums, darting off in every which direction, roaming all over the floor by itself until it hits a corner, then zips back out in another direction. The ball even has its own inner music mode, which when set on, makes the ball perform its amazing light show as it roams the floor in sync with its own music! (The music mode can also be muted.) The ball's action is both sound and touch sensitive. It will turn itself off automatically if left alone, but a simple handclap or touch will get things rolling again. Each RoboGyro ball even comes with a sticker sheet to customize the look of your ball. Uses 3 replaceable AA batteries (not included). The ball is about 4" diameter. Some easy assembly is required.