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Jakubantalik / transitions.dev

transitions-dev

Production-ready CSS transitions for web apps. Use when implementing notification badges, dropdowns, modals, panel reveals, page transitions, card resizes, number pop-ins, text swaps, icon swaps, success checks, avatar group hovers, error state shakes, search/input clear, skeleton loaders, shimmer text, sliding tabs, tooltips, staggered text reveals, card hover tilt, plus-to-menu morph, accordions, toasts, like buttons, learn-more hovers, checkbox checks, spinning counters, toggles, AI thinking states, reasoning streams, streaming text, matrix dot loaders, or banner stacking. Triggers on "add a transition", "animate the dropdown", "make the modal open smoothly", "swap icon", "page slide", "stagger animation", "open / close transition", "make it animate", "fade between", "success animation", "form error", "shake on invalid", "hover lift", "avatar stack hover", "clear the search", "skeleton loader", "loading shimmer", "shimmer text", "sliding tabs", "segmented control", "tooltip", "reveal text", "tilt card", "3D hover tilt", "cursor glare", "plus to menu", "FAB morph", "accordion", "collapsible", "expand / collapse", "disclosure", "toast", "snackbar", "like button", "heart animation", "learn more arrow", "checkbox", "check animation", "spinning counter", "odometer", "slot machine digits", "toggle", "switch", "thinking states", "AI status line", "agent reasoning", "reasoning stream", "streaming text", "stream words in", "matrix loader", "dot loader", "banner stack", "stacked toasts". Also "motion tokens", "scan for ad-hoc transitions", "replace hardcoded durations with motion tokens", "tokenize my animations", and the commands transitions reveal, transitions review, transitions apply, transitions refine.

View sourceMotionInteraction

Install

npx skills add https://github.com/Jakubantalik/transitions.dev --skill transitions-dev

Tabs sliding

When to use

A segmented control / tab bar where the active pill slides between options — view switchers, filter segments, small mutually-exclusive button sets. JS writes the active tab's offsetLeft / offsetWidth onto the pill; CSS owns the tween.

HTML usage

html
<div class="t-tabs" role="tablist">  <span class="t-tabs-pill" aria-hidden="true"></span>  <button class="t-tab" role="tab" aria-selected="true">Plan</button>  <button class="t-tab" role="tab" aria-selected="false">Debug</button>  <button class="t-tab" role="tab" aria-selected="false">Ask</button></div>

Wire-up: On click, flip aria-selected on each tab and write the active tab's offsetLeft / offsetWidth onto the pill: pill.style.transform = translateX(${tab.offsetLeft}px); pill.style.width = ${tab.offsetWidth}px; On first paint and resize, write the same values WITHOUT a transition (suspend with transition: none, force a reflow, restore) so the pill snaps to position before any animation can run.

Tunable variables

VariableDefaultNotes
--tabs-dur250mssourced from --p16-dur
--tabs-easecubic-bezier(0.22, 1, 0.36, 1)sourced from --p16-ease
--tabs-text-mutedrgba(15, 15, 15, 0.8)sourced from --p16-text-muted
--tabs-text-active#0f0f0fsourced from --p16-text-active
--tabs-bar-bg#f1f1f1sourced from --p16-bar-bg
--tabs-pill-bg#ffffffsourced from --p16-pill-bg

The :root defaults below match the live tuning on transitions.dev. Drop them into your global stylesheet once — every transition in this skill reads from semantic names like these, so multiple transitions can share a single :root block.

css
:root {  --tabs-dur: 250ms;  --tabs-ease: cubic-bezier(0.22, 1, 0.36, 1);  --tabs-text-muted: rgba(15, 15, 15, 0.8);  --tabs-text-active: #0f0f0f;  --tabs-bar-bg: #f1f1f1;  --tabs-pill-bg: #ffffff;}

CSS

css
/* The bar is just a flex container with padding for the pill   to sit inside. Tabs sit on z-index: 1, the pill on z-index: 0,   so labels read above the pill background. */.t-tabs {  position: relative;  display: inline-flex;  align-items: center;  gap: 3px;  padding: 3px;  border-radius: 48px;  background: var(--tabs-bar-bg);}.t-tab {  position: relative;  appearance: none;  border: 0;  background: transparent;  height: 30px;  padding: 4px 12px;  color: var(--tabs-text-muted);  cursor: pointer;  border-radius: 48px;  z-index: 1;  transition: color var(--tabs-dur) var(--tabs-ease);}.t-tab:not([aria-selected="true"]):hover,.t-tab[aria-selected="true"] {  color: var(--tabs-text-active);}
/* The pill: width + transform are written inline by JS so   the transition tweens between the previous and next   measured positions. */.t-tabs-pill {  position: absolute;  top: 3px;  left: 0;  height: 30px;  width: 0;  background: var(--tabs-pill-bg);  border-radius: 48px;  transform: translateX(0);  transition:    transform var(--tabs-dur) var(--tabs-ease),    width     var(--tabs-dur) var(--tabs-ease);  will-change: transform, width;  z-index: 0;  pointer-events: none;}
@media (prefers-reduced-motion: reduce) {  .t-tabs-pill, .t-tab { transition: none !important; }}

The @media (prefers-reduced-motion: reduce) guard at the bottom of the snippet is required — keep it. It zeroes the transition for users who have asked for less motion at the OS level.

JavaScript orchestration

js
const bar = document.querySelector(".t-tabs");const pill = bar.querySelector(".t-tabs-pill");const tabs = [...bar.querySelectorAll(".t-tab")];
function moveTo(tab, animate) {  if (!animate) {    const prev = pill.style.transition;    pill.style.transition = "none";    pill.style.transform = `translateX(${tab.offsetLeft}px)`;    pill.style.width = `${tab.offsetWidth}px`;    void pill.offsetWidth;    pill.style.transition = prev;  } else {    pill.style.transform = `translateX(${tab.offsetLeft}px)`;    pill.style.width = `${tab.offsetWidth}px`;  }}const active = () =>  tabs.find((t) => t.getAttribute("aria-selected") === "true") || tabs[0];
tabs.forEach((tab) => {  tab.addEventListener("click", () => {    tabs.forEach((t) =>      t.setAttribute("aria-selected", t === tab ? "true" : "false")    );    moveTo(tab, true);  });});requestAnimationFrame(() => moveTo(active(), false));window.addEventListener("resize", () => moveTo(active(), false));