The CDI 22ER9012 Roller Controller is a controller for the Philips CD-i. It was designed after extensive studies by CTW and was build by Kun Ring Enterprises. However the working principle is simple. Depending on which way you role, two rods with radars function as input devices (see video). Simple but effective.

The Roller Controller is specifically made for little children. The ergonomic design makes it easy  to  use  with  one or two hands. By simply rotating the ball, you move  the  cursor  across  the  CD-I  display screen to point at any desired feature, then select the feature by  pressing  one  of  the  action buttons.

The controller is also often used by adults to play Full Motion Video games wherein you have to point and shoot, like Solar Crusade. This is because the Roller Controller makes aiming much easier than many of the more regular CD-i controllers.