ai-for-dummies/.agents/skills/motion/SKILL.md

name, description

name	description
motion	Add or review animation on the ai-for-dummies site — transitions, state changes, view transitions. Use when any element moves, fades, or transforms, or when auditing existing motion for performance and reduced-motion support.

Motion

This is an editorial-print design. Motion is punctuation. Read ../../rules/animation.md — it is binding; this is the procedure.

Decide it should move

Answer out loud: what does this motion tell the user that the static state does not? Valid answers: something changed, attention needs directing to what changed, a layout shift needs smoothing. "It feels more polished" is not an answer — on this design it reads as generic.

If there is no answer, ship it static. That is a legitimate, common outcome.

Build it

.panel {
  transition:
    opacity 180ms cubic-bezier(0.2, 0, 0, 1),
    transform 180ms cubic-bezier(0.2, 0, 0, 1);
}
.panel[data-state='entering'] {
  opacity: 0;
  transform: translateY(6px);
}

• transform and opacity only. Animating width/height/top/left forces layout every frame and shows up as a failed INP (budget: 200ms).
• 150–250ms for UI feedback; up to 400ms for a page transition.
• One thing moves at a time. No staggered card cascades.
• will-change only immediately before animating, removed after.
• No animation library. This site's thesis is having no runtime dependencies.

Reduced motion is not optional

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

Then test it: DevTools → Rendering → Emulate prefers-reduced-motion: reduce. The end state must still be correct and the UI still usable. Reduced, not broken.

Page transitions

Astro's <ClientRouter /> is the only sanctioned motion dependency. Before enabling it, verify:

• JS disabled → full navigation still works
• browser back/forward still works
• the review desk's query-param deep links survive
• prefers-reduced-motion is honoured

Audit an existing animation

grep -rn "transition\|animation\|@keyframes\|transform" src/ --include="*.astro" --include="*.css"

For each hit ask: does it animate a layout property? does it respect reduced motion? is there a stated purpose? Three questions, three possible fixes.