# Matrix Rain — Design Spec
**Date:** 2026-05-11
**Repo:** repo-html-structure (`packages.danix.xyz`)
## Goal
Add the matrix rain canvas animation to the `_header.html` of the Slackware package repository, matching the implementation in `danix2-hugo-theme` as closely as possible for brand consistency.
## Architecture
### New file: `.assets/matrix-rain.js`
Served from `$PKGREPO/.assets/matrix-rain.js` (i.e. `https://packages.danix.xyz/.assets/matrix-rain.js`).
Source: `danix2-hugo-theme/assets/js/matrix-rain.js` with minimal adaptations (see below). No logic changes — rendering engine, trail model, CSS var integration, font-ready wait, debounced resize, MutationObserver for theme switching all carried over verbatim.
**Adaptations from danix2 version:**
| danix2 | This repo |
|--------|-----------|
| Canvas = `#matrix-rain`, full window width/height | Canvas appended to `.site-header`, width = 65% of header width, height = header height |
| No fade overlay | Gradient fade `
` over left 75% of canvas (matches cgit approach) |
| `canvas.width = window.innerWidth` | `canvas.width = Math.floor(header.offsetWidth * 0.65)` |
| `canvas.height = window.innerHeight` | `canvas.height = header.offsetHeight` |
| Resize: `resizeCanvas()` uses `window.innerWidth/Height` | Resize: recalculate from `header.offsetWidth/Height` |
| Canvas positioned full-screen fixed | Canvas `position:absolute; top:0; right:0; height:100%; pointer-events:none; z-index:0` |
Everything else (character set, trail rendering, color sampling, `hexToRgba`, `sampleColors`, `MutationObserver`, `document.fonts.ready`, debounced resize) is identical.
### CSS variable addition: `--accent2`
Add to `:root` in the `CSS=` heredoc in `gen_web_hook.sh`:
```css
--accent2: #4ec97b;
```
This matches the existing `--green` value and aligns the var name with danix2-hugo-theme.
The script references `--accent2` (green rain) and `--accent` (purple rain) — both already present in this repo's palette.
### Header structure change (in `gen_web_hook.sh` → `write_header()`)
Add `position: relative` to `.site-header` so the absolutely-positioned canvas is contained within it.
Add `` to the `` of every generated `_header.html`.
The canvas and fade `
` are injected by the JS itself (matching cgit pattern) — no HTML changes needed beyond the `