Product Principle:

When a small circle is tangent internally to a larger circle and rolls along the circumference of the larger circle, if the diameter of the small circle is exactly half the diameter of the larger circle, then the trajectory of any point on the edge of the small circle will be a straight line passing through the center of the larger circle. Therefore, by rotating the handle, the small circle performs pure rolling within the larger circle, causing a point on the small circle to move back and forth in a straight line.

Gameplay Points:

Gently rotate the handle at a steady speed and observe the pure rolling of the small circle within the larger circle, where a point on the small circle moves back and forth in a straight line.