To transmit a complete motion sequence to the computer, the joystick needs to measure its position on two axes: the X-axis (from left to right) and the Y-axis (from top to bottom). As in basic geometry, the X-Y coordinate system precisely indicates the joystick's location.
In a standard joystick design, a gamepad moves a narrow rod mounted on two rotatable slotted axes. Moving the joystick back and forth rotates the Y-axis from one side to the other. Moving it left and right rotates the X-axis. Moving the joystick diagonally rotates both axes simultaneously. When you release the joystick, several springs return it to its central position.
A joystick control system only needs to monitor the position of each axis to determine the joystick's position. Traditional analog joysticks achieve this using two voltage dividers or variable resistors.
