The Mechanical Mouse
What can be said about a mouse with a ball? It did the job back in the day, and can still be found hanging out on retail shelves next to optical designs. The technology was simple: use a large, rubber ball to move two rollers mounted within the device. In turn, these rollers (one registering movement on the X axis and one on the Y) caused two disc-like encoder wheels to operate and disrupt optical beams. Electrical signals generated from the disruption were processed by the device drivers, converting them to movement onscreen.
The drawback to this method was that the ball picked up gunk from the user's desk, whether it was food, dust, or whatever else was on the surface. A mouse pad would help reduce the filth, however the gunk would eventually collect on the two rollers, causing the mouse to act sluggish. This was a pain when it came to gaming, especially when playing first-person shooters where mouse-look movement was critical. Typically, users had to remove the ball and clean the rollers by scraping off the hardened gunk. We can't say we really miss the mechanical mouse. However, it was definitely better than playing with a joystick or gamepad.