What mechanism does a mechanical mouse use to sense movement?

A mechanical mouse uses a ball as its primary mechanism to sense movement. The ball is positioned on the underside of the mouse and rolls in response to movement across a surface. As the ball turns, it drives two wheels inside the mouse—one that detects horizontal movement and another for vertical movement. These wheels alter the position of a cursor on a computer screen based on the direction and speed of movement detected by the mouse.

The ball allows for both x-axis and y-axis movement detection, translating physical movement into digital signals that the computer interprets to control the cursor. This design was prevalent before the advent of optical and laser mice, which use different technologies to achieve similar functions without a physical rolling component.