motion-ui

SKILL.md

Motion System v4.2

Production-ready UI motion system for React / Next.js.

Focused on performance, accessibility, and usability — not decoration.

When to Use

Use this motion system when motion:

Guides attention (e.g., onboarding, key actions)

Communicates state (loading, success, error, transitions)

Preserves spatial continuity (layout changes, navigation)

Appropriate Scenarios

Interactive components (buttons, modals, menus)

State transitions (loading → loaded, open → closed)

Navigation and layout continuity (shared elements, crossfade)

Considerations

Accessibility: Always support reduced motion

Device adaptation: Adjust for low-end devices

Performance trade-offs: Prefer responsiveness over visual smoothness

Avoid Using Motion When

It is purely decorative

It reduces usability or clarity

It impacts performance negatively

How It Works

Core Principle

Motion must:

Guide attention

Communicate state

Preserve spatial continuity

If it does none → remove it.

Installation

npm install motion

Version

motion/react - default for current Motion for React projects (package: motion)

framer-motion - legacy import path for projects that still depend on Framer Motion

Do not mix. Mixing causes conflicting internal schedulers and broken AnimatePresence contexts — components from one package will not coordinate exit animations with components from the other.

To check which version your project uses:

cat package.json | grep -E '"motion"|"framer-motion"'

Always import from one source consistently:

// Correct (modern)
import { motion, AnimatePresence } from "motion/react"

// Correct (legacy)
import { motion, AnimatePresence } from "framer-motion"

// Never mix both in the same project

Motion Tokens

// motionTokens.ts
export const motionTokens = {
  duration: {
    fast: 0.18,
    normal: 0.35,
    slow: 0.6
  },
  // Use these as the `ease` value inside a `transition` object:
  // transition={{ duration: motionTokens.duration.normal, ease: motionTokens.easing.smooth }}
  easing: {
    smooth: [0.22, 1, 0.36, 1] as [number, number, number, number],
    sharp:  [0.4,  0, 0.2, 1] as [number, number, number, number]
  },
  distance: {
    sm: 8,
    md: 16,
    lg: 24
  }
}

Usage example:

import { motionTokens } from "@/lib/motionTokens"

<motion.div
  initial={{ opacity: 0, y: motionTokens.distance.md }}
  animate={{ opacity: 1, y: 0 }}
  transition={{
    duration: motionTokens.duration.normal,
    ease: motionTokens.easing.smooth
  }}
/>

Performance Rules

Safe

transform

opacity

Avoid

width / height

top / left

Rule: responsiveness > smoothness

Device Adaptation

The heuristic combines CPU core count and available memory for a more reliable signal. deviceMemory is available on Chrome/Android; the fallback covers Safari and Firefox.

const isLowEnd =
  typeof navigator !== "undefined" && (
    // Low memory (Chrome/Android only; undefined elsewhere → treat as capable)
    (navigator.deviceMemory !== undefined && navigator.deviceMemory <= 2) ||
    // Few cores AND no memory API (covers Safari/Firefox on weak hardware)
    (navigator.deviceMemory === undefined && navigator.hardwareConcurrency <= 4)
  )

const duration = isLowEnd ? 0.2 : 0.4

Accessibility

JS (useReducedMotion)

import { motion, useReducedMotion } from "motion/react"

export function FadeIn() {
  const reduce = useReducedMotion()

  return (
    <motion.div
      initial={{ opacity: 0, y: reduce ? 0 : 24 }}
      animate={{ opacity: 1, y: 0 }}
    />
  )
}

CSS

@media (prefers-reduced-motion: reduce) {
  .motion-safe-transition {
    transition: opacity 0.2s;
  }

  .motion-reduce-transform {
    transform: none !important;
  }
}

Tailwind

<div class="motion-safe:animate-fade motion-reduce:opacity-100"></div>

Architecture & Patterns

Core Patterns

Scenario
Pattern

Hover feedback
whileHover

Tap / press feedback
whileTap

Reveal on scroll
whileInView

Scroll-linked value
useScroll + useTransform

Conditional mount/unmount
AnimatePresence

Small layout shifts (single element, < ~300px change)
layout prop

Large layout shifts or full-page reflows
Avoid layout; use CSS transitions or page-level routing instead

Complex, imperative sequences
useAnimate

Why avoid layout on large containers? Framer's layout animation uses transform to reconcile positions, but on elements that span the full viewport or trigger deep reflow, the measurement cost causes visible jank and CLS. Prefer CSS Grid/Flexbox transitions or coordinate with layoutId on specific child elements only.

Layout & Transitions

Shared element transitions → layoutId (must be unique per mounted instance)

Enter / exit transitions → AnimatePresence (see mode guidance below)

AnimatePresence mode

Always specify mode explicitly — the default ("sync") runs enter and exit simultaneously, which causes visual overlap in most UI patterns.

mode
When to use

"wait"
Exit completes before enter starts. Use for modals, toasts, page transitions.

"sync" (default)
Enter and exit overlap. Use only when overlap is intentional (e.g., crossfade carousels).

"popLayout"
Exiting element is popped out of flow immediately; remaining items animate to fill. Use for lists, tabs, dismissible cards.

// Modal — always use "wait"
<AnimatePresence mode="wait">
  {open && <Modal key="modal" />}
</AnimatePresence>

// Dismissible list item — use "popLayout"
<AnimatePresence mode="popLayout">
  {items.map(item => <Card key={item.id} />)}
</AnimatePresence>

Advanced Patterns (Concepts)

Parallax (scroll-linked transforms)

Scroll storytelling (sticky sections)

3D tilt (pointer-based transforms)

Crossfade (shared layoutId)

Progressive reveal (clip-path)

Skeleton loading (looped opacity)

Micro-interactions (hover/tap feedback)

Spring system (physics-based motion)

Modal Essentials

Focus trap

Escape close

Scroll lock

ARIA roles

Use AnimatePresence mode="wait" so exit animation completes before the next modal enters

Full Example

import React, { useEffect, useRef, useState } from "react"
import { motion, AnimatePresence } from "motion/react"

function useFocusTrap(ref: React.RefObject<HTMLDivElement | null>, active: boolean) {
  useEffect(() => {
    if (!active || !ref.current) return
    const el = ref.current
    const focusable = el.querySelectorAll<HTMLElement>(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    )
    const first = focusable[0]
    const last  = focusable[focusable.length - 1]

    function handleKey(e: KeyboardEvent) {
      if (e.key !== "Tab") return
      if (e.shiftKey && document.activeElement === first) {
        e.preventDefault()
        last?.focus()
      } else if (!e.shiftKey && document.activeElement === last) {
        e.preventDefault()
        first?.focus()
      }
    }

    el.addEventListener("keydown", handleKey)
    first?.focus()
    return () => el.removeEventListener("keydown", handleKey)
  }, [active, ref])
}

function useScrollLock(active: boolean) {
  useEffect(() => {
    if (!active) return
    const prev = document.body.style.overflow
    document.body.style.overflow = "hidden"
    return () => { document.body.style.overflow = prev }
  }, [active])
}

function Modal({ open, closeModal }: { open: boolean; closeModal: () => void }) {
  const ref = useRef<HTMLDivElement>(null)

  useFocusTrap(ref, open)
  useScrollLock(open)

  useEffect(() => {
    function onKey(e: KeyboardEvent) {
      if (e.key === "Escape") closeModal()
    }
    if (open) window.addEventListener("keydown", onKey)
    return () => window.removeEventListener("keydown", onKey)
  }, [open, closeModal])

  return (
    // mode="wait" ensures exit animation finishes before any new modal enters
    <AnimatePresence mode="wait">
      {open && (
        <motion.div
          role="dialog"
          aria-modal="true"
          aria-labelledby="modal-title"
          initial={{ opacity: 0 }}
          animate={{ opacity: 1 }}
          exit={{ opacity: 0 }}
          transition={{ duration: 0.2 }}
          className="fixed inset-0 flex items-center justify-center bg-black/40"
        >
          <motion.div
            ref={ref}
            initial={{ scale: 0.95, opacity: 0 }}
            animate={{ scale: 1,    opacity: 1 }}
            exit={{    scale: 0.95, opacity: 0 }}
            transition={{ duration: 0.2, ease: [0.22, 1, 0.36, 1] }}
            className="bg-white p-6 rounded"
          >
            <h2 id="modal-title">Dialog Title</h2>
            <button onClick={closeModal}>Close</button>
          </motion.div>
        </motion.div>
      )}
    </AnimatePresence>
  )
}

export function Example() {
  const [open, setOpen] = useState(false)

  return (
    <>
      <button onClick={() => setOpen(true)}>Open</button>
      <Modal open={open} closeModal={() => setOpen(false)} />
    </>
  )
}

SSR Safety

Match initial states between server and client renders

Avoid implicit animation origins (always set initial explicitly)

Wrap motion components in "use client" in Next.js App Router

Debugging

Check:

Wrong import (mixing motion/react and framer-motion)

Missing "use client" directive in Next.js App Router

Missing key prop on AnimatePresence children

Hydration mismatch (initial state differs between SSR and client)

layout prop misuse on large containers causing reflow jank

State-driven animation not triggering (check dependency arrays)

QA

No CLS

Keyboard works

Focus trapped in modals

ARIA roles correct (role="dialog", aria-modal="true")

Reduced motion respected (useReducedMotion + CSS media query)

No hydration warnings in Next.js

Animations stop cleanly on unmount (no memory leaks)

AnimatePresence mode set explicitly on all usage sites

Anti-Patterns

Animating layout properties (width, height, top, left)

Infinite animations without purpose (always ask: what state does this communicate?)

Over-staggering lists (keep staggerChildren ≤ 0.1s; beyond that it feels slow)

Ignoring reduced motion preferences

Using layout on large or full-viewport containers

Omitting mode on AnimatePresence (default "sync" causes visual overlap)

Using motion purely for decoration

Philosophy

Motion is interaction design.

Final Rule

If motion does not improve UX → remove it.

Examples

Button Interaction

import { motion } from "motion/react"

export function Button() {
  return (
    <motion.button
      whileHover={{ scale: 1.02 }}
      whileTap={{ scale: 0.97 }}
      transition={{ duration: 0.15, ease: [0.4, 0, 0.2, 1] }}
    >
      Click me
    </motion.button>
  )
}

Reduced Motion Example

import { motion, useReducedMotion } from "motion/react"

export function FadeIn() {
  const reduce = useReducedMotion()

  return (
    <motion.div
      initial={{ opacity: 0, y: reduce ? 0 : 24 }}
      animate={{ opacity: 1, y: 0 }}
      transition={{ duration: reduce ? 0.1 : 0.35, ease: [0.22, 1, 0.36, 1] }}
    />
  )
}

Stagger List

import { motion } from "motion/react"

const container = {
  hidden: {},
  visible: {
    transition: { staggerChildren: 0.08 } // keep ≤ 0.1s to avoid sluggishness
  }
}

const item = {
  hidden:  { opacity: 0, y: 10 },
  visible: { opacity: 1, y: 0,  transition: { duration: 0.3, ease: [0.22, 1, 0.36, 1] } }
}

export function List() {
  return (
    <motion.ul variants={container} initial="hidden" animate="visible">
      {[1, 2, 3].map(i => (
        <motion.li key={i} variants={item}>Item {i}</motion.li>
      ))}
    </motion.ul>
  )
}

Modal with AnimatePresence

import { motion, AnimatePresence } from "motion/react"

export function Modal({ open }: { open: boolean }) {
  return (
    <AnimatePresence mode="wait">
      {open && (
        <motion.div
          initial={{ opacity: 0, scale: 0.95 }}
          animate={{ opacity: 1, scale: 1    }}
          exit={{    opacity: 0, scale: 0.95 }}
          transition={{ duration: 0.2, ease: [0.22, 1, 0.36, 1] }}
        />
      )}
    </AnimatePresence>
  )
}

Scroll Parallax

import { useScroll, useTransform, motion } from "motion/react"

export function Parallax() {
  const { scrollYProgress } = useScroll()
  const y = useTransform(scrollYProgress, [0, 1], [0, -80])

  return <motion.div style={{ y }} />
}

Skeleton Loading

import { motion } from "motion/react"

export function Skeleton() {
  return (
    <motion.div
      className="bg-gray-200 h-6 w-full rounded"
      animate={{ opacity: [0.5, 1, 0.5] }}
      transition={{
        duration: 1.5,       // comfortable pulse — was missing, caused fast flash
        repeat: Infinity,
        ease: "easeInOut"
      }}
    />
  )
}

Shared Layout (Crossfade)

import { motion } from "motion/react"

// layoutId must be unique per mounted instance.
// If multiple instances can exist simultaneously, append a unique id:
// layoutId={`shared-${item.id}`}
export function Shared() {
  return <motion.div layoutId="shared" />
}