Generative Geometry

Spirograph

A hypotrochoid spirograph traced progressively on canvas with a shifting hue; each cycle completes then resets with new random radii and color.

canvasmedium complexitymoderate motionclick

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Live demo — the real component, running in a sandbox. One self-contained HTML file, zero dependencies. Open it on the canvas →

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When to use it

Dark-mode hero backgrounds, generative art showcases, math/geometry-themed pages needing ambient motion.

When not to

Light-background layouts (background hardcoded dark navy). Contexts needing static or text-legible overlays.

Working with an AI agent

Every component ships agent-ready metadata. An example instruction for this one:

Change the hue rotation speed from 30 to 60 in the strokeStyle line, increase lineWidth from 1.8 to 2.5, and set the starting hue to a fixed value like 200 for a consistent blue palette. Theme: dark tokens live in :root, the light variant in :root[data-theme="light"]; ?theme=light or a {type:'forever:theme'} postMessage switches at runtime.

Safe to edit

hue shift speed (prog*30 multiplier)
line width (1.8)
trace span per frame (0.10+boost)
trail fade (--gg04-fade alpha 0.028: lower = longer trail)
mount pre-roll (90 frames drawn before first paint)
radius scale factor (s*0.42)
inner radius range (0.18+random*0.28)
pen distance range (0.4+random*0.5)
theme tokens (:root dark defaults + [data-theme=light] overrides)

Keep intact

GCD-based cycle calculation (ensures clean closure)
DPR-aware canvas sizing
visibilitychange pause
reduced-motion static fallback
theme hook (?theme= bootstrap + forever:theme message listener + theme tokens)

Known limitations

Background color hardcoded in CSS and fillRect — must change both to alter backdrop
pointerdown boost is subtle; no visual feedback on click
cyc computed from rounded R/r may produce very long cycles for certain random values

spirographhypotrochoidgenerativecanvasgeometryloopcolor-shift

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Moiré InterferenceThree drifting concentric ring sets in cyan, pink, and green blend additively to create shifting moiré patterns. Pointer steers one ring center.