Have you ever had to use a trackball? 🖲

The trackball has been around for perhaps as long as the mouse - after all, it does the same thing by the same method, measuring displacement in two directions by the ball rotating two slotted discs at right angles to each other, past photo-electric sensors.

It was and as far as know still is, particularly used in larger and better forms than those on lap-tops, for maritime, military and some industrial applications where a mouse would obviously be impracticable.