Spirograph — drawing rosettes with gear ratios

Spirograph reproduces the classic plastic toy in a browser. A small wheel rolls inside a bigger one, and a pen at offset distance d traces a rosette curve called a hypotrochoid. Three sliders let you tweak the gear sizes and the offset; the curve redraws live as you move them.

How to play

The pen is always running at the center of the canvas. By default it leaves only a faint sketch that fully vanishes after about two seconds — so you can tune R, r, d, pick an ink color, or hit Shuffle for a fresh random shape, all without committing anything. When the rosette feels right, hit DRAW to commit ink to the permanent trail in the chosen color. Hit it again to stop. PNG saves the result, Reset clears everything.

Why it's satisfying

The original Spirograph (Denys Fisher, 1965) sold tens of millions of copies because the math is genuinely magical — three numbers, infinite curves. The browser version removes the only annoying part: the pencil never slips out of the hole.

About

Spirograph is part of Alcy, thirty free contemplative micro-games in your browser. For more pattern art: Kaleidoscope, Bloom, Loop Maker.