Spirograph! What fun!
A Spirograph is a geometric drawing toy that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. It was developed by British engineer Denys Fisher and first sold in 1965.
"Spirograph" has also been used to describe a variety of software applications that display similar curves. It has also been applied to the class of curves that can be produced with the drawing equipment, and therefore may be regarded as a synonym of hypotrochoid. The name has been a registered trademark of Hasbro, Inc., since it bought the Denys Fisher company.
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