Components
Every duration, distance and easing below comes from a token. Nothing here hard-codes a number, which is why one change to theme.ts retimes a whole site.
Turn on reduced motion in your OS and reload: everything still arrives, and nothing travels. That is the rule, and it is not configurable.
Scroll this panel ↓
Slides in from the right, once. Jump down the panel and all three enter together — the stagger is what stops that reading as one block.
Slides in from the right, once. Jump down the panel and all three enter together — the stagger is what stops that reading as one block.
Slides in from the right, once. Jump down the panel and all three enter together — the stagger is what stops that reading as one block.
Rises 20px and fades as the page becomes visible.
npm run build
Emphasis is a filled chip that settles.
Travels 2px. More reads as the card coming loose.
The panel snaps open. Only the marker rotates.
The panel snaps open. Only the marker rotates.
Continuous motion tied to the scroll wheel is the strongest trigger for vestibular symptoms there is, so these are gated on the media query directly and stop entirely — no site-wide policy, no per-element opt-out.
The bar above tracks how far through this panel you are, and reaches 100% exactly as the last line reaches the bottom.
It is driven by one scroll listener, throttled with requestAnimationFrame so a trackpad flick writes once per frame rather than dozens of times per frame.
Every layout read happens before every write. Interleaving them forces the browser to recompute layout mid-frame, which is what turns a progress bar from free into a jank source.
The travel is the content height minus one viewport height. That subtraction is the part everyone leaves out.
Without it, the bar tops out around 80% on a long document and never fills — which reads as broken rather than as a design choice.
It is clamped at both ends, because rubber-band scrolling on iOS reports a negative position at the top and an over-height one at the bottom.
A ResizeObserver watches the panel too. Height changes without a scroll — images loading, a font swapping, a filter hiding rows — would otherwise leave the bar stale until the next move.
The bar is aria-hidden. It restates what the scrollbar already carries natively and more precisely, so it earns its place visually rather than semantically.
Announcing "thirty-seven percent" to a screen reader would be noise on top of a control that user already has.
On a real page this shares its listener with the scroll-to-top button and anything else that needs scroll position.
Two listeners each doing their own rAF throttle means two callbacks, two layout reads and two chances to force a synchronous reflow on every frame of every scroll.
On the one page type where scrolling smoothly is the entire product, that is not a trade worth making.
Keep scrolling — there is a little more, so the bar has somewhere left to go.
That is the end. The bar should be full.
Worth a look when CSS genuinely will not do it. The bar for adding a dependency is high — demo3 draws a rotating wireframe sphere in about 120 lines of vanilla canvas, against the 331 KB of libraries the design it follows uses for the same effect.