Marcos Paulo
79920c9e6c
Three strands of work on the chapter surface, all reading from the same constraint: this site ships no runtime dependencies, so every effect below is native CSS or an .astro component. Motion (src/styles/motion.css, DrawRule.astro). A scroll-driven layer of reveals, hero parallax, section depth, and a hairline that paints itself along its path, scrubbed by `animation-timeline: view()` — 0KB against lottie-web's ~60KB gzipped on the main thread. Every scrubbed rule sits inside `prefers-reduced-motion: no-preference` and `@supports`, so a Firefox reader or an opted-out one gets the complete static page rather than one with holes in it. Ranges key to `cover 40%`-`cover 75%` where the motion is meant to be watched: `view()` ranges key to first visibility, which on a 2600px page is long before anyone is reading the section. `.agents/skills/motion/references/scroll-driven.md` records the technique and the two ways `pathLength` normalisation was broken while building it. Diagrams (StepFlow.astro, WorktreeMap.astro). The `.steps` stack on /skills/, /models/, and /agents/ becomes a numbered flow with connectors, and /agents/ grows the worktree map it was describing in prose — reusing the `trees` collection rather than a second set of strings. The map's static variant is gated one class deeper than full-guide's page styles, so the interactive copy renders byte-identical. Connectors are pseudo-elements, not SVG: a stretched path desynchronises its own dash pattern, and a straight line does not need one. Mermaid was considered and rejected at ~1MB of runtime. Retrieval practice (/rules/, /skills/). A "check yourself" section of native `<details>` question/answer pairs plus a citation row, both bilingual through the existing `data-copy` toggle, and both JavaScript-free. Two audit blind spots surfaced and are closed rather than worked around: `build.inlineStylesheets: 'never'`, because Astro inlined sheets under ~4kB and audit-ui.mjs reads its colour and size baseline from dist/_astro/*.css; and `--columns` declared in the grid components, because an element-level custom property is not a declaration the audit can resolve. legacy/styles/skills.css is renamed and imported for its side effect. Inside a *page*, `?url` resolves to that page's own CSS chunk whatever file it names, so the link pointed at the wrong asset and the sheet was emitted but never loaded — the package preview had been rendering unstyled and overflowing since the Astro cutover. verify.mjs gains 5 assertions for the recall sections and their Portuguese copy: 89 now, against the 84 baseline. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
84 lines
2.7 KiB
Markdown
84 lines
2.7 KiB
Markdown
---
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name: motion
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description:
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Add or review animation on the ai-for-dummies site — transitions, state
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changes, view transitions. Use when any element moves, fades, or transforms,
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or when auditing existing motion for performance and reduced-motion support.
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---
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# Motion
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This is an editorial-print design. Motion is punctuation. Read
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[`../../rules/animation.md`](../../rules/animation.md) — it is binding; this is
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the procedure.
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## Decide it should move
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Answer out loud: **what does this motion tell the user that the static state
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does not?** Valid answers: something changed, attention needs directing to what
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changed, a layout shift needs smoothing. "It feels more polished" is not an
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answer — on this design it reads as generic.
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If there is no answer, ship it static. That is a legitimate, common outcome.
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## Build it
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```css
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.panel {
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transition:
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opacity 180ms cubic-bezier(0.2, 0, 0, 1),
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transform 180ms cubic-bezier(0.2, 0, 0, 1);
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}
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.panel[data-state='entering'] {
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opacity: 0;
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transform: translateY(6px);
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}
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```
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- **`transform` and `opacity` only.** Animating `width`/`height`/`top`/`left`
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forces layout every frame and shows up as a failed INP (budget: 200ms).
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- 150–250ms for UI feedback; up to 400ms for a page transition.
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- One thing moves at a time. No staggered card cascades.
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- `will-change` only immediately before animating, removed after.
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- No animation library. This site's thesis is having no runtime dependencies.
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- Scroll-scrubbed motion (reveals, parallax, depth, line draw) has its own rules
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— ranges, feature gates, the `linear` exception, SVG line drawing. Read
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[`references/scroll-driven.md`](references/scroll-driven.md) before touching
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`src/styles/motion.css`.
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## Reduced motion is not optional
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```css
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@media (prefers-reduced-motion: reduce) {
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* {
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animation-duration: 0.01ms !important;
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animation-iteration-count: 1 !important;
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transition-duration: 0.01ms !important;
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scroll-behavior: auto !important;
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}
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}
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```
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Then **test it**: DevTools → Rendering → Emulate
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`prefers-reduced-motion: reduce`. The end state must still be correct and the UI
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still usable. Reduced, not broken.
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## Page transitions
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Astro's `<ClientRouter />` is the only sanctioned motion dependency. Before
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enabling it, verify:
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- JS disabled → full navigation still works
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- browser back/forward still works
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- the review desk's query-param deep links survive
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- `prefers-reduced-motion` is honoured
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## Audit an existing animation
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```bash
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grep -rn "transition\|animation\|@keyframes\|transform" src/ --include="*.astro" --include="*.css"
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```
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For each hit ask: does it animate a layout property? does it respect reduced
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motion? is there a stated purpose? Three questions, three possible fixes.
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