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Spirograph

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About

Spirograph traces hypotrochoids — the looping curves a pen makes through a gear rolling inside a ring. Three sliders (ring R, gear r, pen offset d) reshape the figure live; randomize to stumble onto a nice one.

How it works

It plots the parametric hypotrochoid x=(R−r)cos t + d cos((R−r)/r·t), y=(R−r)sin t − d sin((R−r)/r·t) onto a canvas. The number of loops before the curve closes comes from r / gcd(R, r). No images, no backend.

Metadata
title
Spirograph
description
A browser spirograph — drag three sliders and watch hypotrochoid curves bloom on a canvas. Randomize for endless patterns.
canonical
https://kaspirius.com/spirograph
updated
Last updated
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TechArticle

Same as Article, flagged as technical/developer reference material.

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  "@type": "TechArticle",
  "headline": "Spirograph — toy",
  "description": "A browser spirograph — drag three sliders and watch hypotrochoid curves bloom on a canvas. Randomize for endless patterns.",
  "url": "https://kaspirius.com/spirograph",
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  "datePublished": "2026-06-18",
  "dateModified": "2026-06-18",
  "author": {
    "@type": "Person",
    "name": "kaspirius",
    "url": "https://kaspirius.com"
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  "publisher": {
    "@type": "Organization",
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    "url": "https://kaspirius.com"
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