[csswg-drafts] Proposal: Scroll-Reactive Rainbow Background using CSS Houdini Paint Worklet (#12966)

mtechamit has just created a new issue for https://github.com/w3c/csswg-drafts:

== Proposal: Scroll-Reactive Rainbow Background using CSS Houdini Paint Worklet ==
Proposal: Scroll-Reactive Rainbow Background using CSS Houdini Paint Worklet

A creative experiment showcasing a  "scroll-reactive rainbow background" built entirely using the "CSS Houdini Paint Worklet API".

As the user scrolls, the hue value rotates smoothly from 0° to 360°, creating a dynamic neon-like rainbow background — without using any heavy JavaScript animations.

Demo
Live Demo:https://mtechamit.github.io/rainbow-houdini/

Worklet Source: 
https://github.com/mtechamit/rainbow-houdini
https://mtechamit.github.io/rainbow-houdini/rainbow-scroll.js

---

Key Features
- **Scroll-based color animation:** Hue changes relative to scroll position.  
- **Smooth easing:** Transitions are fluid and GPU-friendly.  
- **Pure Houdini rendering:** All drawing logic handled in the Paint Worklet.  
- **Minimal JS:** Only one CSS custom property (`--scroll-pos`) is updated.  
- **Works in Chrome/Edge** using PaintWorklet API.



 Why This Matters
This project highlights the potential of **CSS Houdini Paint API** for interactive and reactive visual effects.  
It suggests a possible future direction for native **scroll-linked color or gradient animations** directly in CSS — without external JS or worklets.

Possible Extensions
-Allow hue rotation or animation timelines to be defined directly in CSS (e.g., via `animation-timeline: scroll()` or a new `scroll-hue()` function).  
- Extend Paint API to have built-in hooks for scroll progress.  
- Could serve as an official educational example for **Houdini Paint API** in CSS specifications.


Suggested Tags
CSS, Houdini, PaintWorklet, Proposal, Scroll-linked Animation



Thank you for reviewing this experimental proposal — feedback and discussion are very welcome!

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12966 using your GitHub account


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Received on Friday, 17 October 2025 06:35:07 UTC