A small circle rolling inside a large circle traces a star-shaped pattern
Like a Spirograph toy, when a small circle rolls without slipping inside a larger circle, the curve traced by a point on the small circle is called a hypocycloid. The pattern changes completely depending on the ratio of the two radii.
Formula: When the large circle has radius R and the small circle has radius r, if R/r is an integer n, a star shape with n points is completed. If R/r is not an integer, the pattern never closes and keeps drawing new lines.