A memory of a small toy given by Xiang Shan's parents flashed through his mind.
The spirograph, also known as the Spirograph in English, is a once-popular drawing toy. This toy prototype was invented by a Polish mathematician in the late 19th century and was introduced to the mainland in 1976. A circular or annular frame with internal teeth and one or more small gears with external teeth and small holes that can roll inside the outer ring. When using it, the outer ring is fixed on the desktop, the gear is placed inside the outer ring and meshed with it, a pen is inserted into one of the holes on the gear, and the gear is pushed to roll within the outer ring. Through the engagement and movement of different gears, anyone can easily create complex and beautiful curves like blooming flowers.
One winter, Xiang Shan's father took him to a street stall and bought him a set.
