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+---
+name: motion-foundations
+description: Motion tokens, spring presets, performance rules, device adaptation, accessibility enforcement, and SSR safety for React / Next.js using motion/react. Foundation layer — all other motion skills depend on this.
+version: 1.0
+tags: [motion, animation, performance, accessibility]
+category: frontend
+author: jeff
+---
+
+# Motion Foundations
+
+The base layer of the motion system. Defines every value, constraint, and
+rule that downstream skills (`motion-patterns`, `motion-advanced`) inherit.
+Load this skill before any animation work begins.
+
+## When to Activate
+
+- Starting any animated component from scratch
+- Setting up tokens, spring presets, or easing values
+- Implementing `prefers-reduced-motion` support
+- Debugging hydration mismatches from animation initial states
+- Evaluating whether an animation should exist at all
+
+## Outputs
+
+This skill produces:
+
+- A shared `motionTokens` object (duration, easing, distance, scale)
+- A shared `springs` preset map (5 named configs)
+- A `shouldAnimate` boolean gate used by all components
+- Accessibility-compliant animation defaults via `useReducedMotion`
+- SSR-safe initial states with zero hydration warnings
+
+## Principles
+
+Motion must do at least one of the following or it must be removed:
+
+- Guide attention
+- Communicate state
+- Preserve spatial continuity
+
+Responsiveness always outranks smoothness. A 60 fps animation that causes
+input delay is worse than no animation.
+
+## Rules
+
+These are non-negotiable. They apply to every component in the system.
+
+1. **Use `motion/react` only.** Never import from `framer-motion`. Never mix the two in the same tree.
+2. **`initial` must match server output.** If the server renders `opacity: 1`, the `initial` prop must also be `opacity: 1`. No exceptions.
+3. **Reduced motion overrides everything.** When `useReducedMotion()` returns `true` or `prefersReduced` is `true`, all transforms are disabled. Opacity-only fades at ≤ 0.2s are the only permitted fallback.
+4. **Never animate layout properties.** `width`, `height`, `top`, `left`, `margin`, `padding` are banned from `animate`. Use `transform` and `opacity` only.
+5. **All token values come from `motionTokens`.** Hardcoded durations and easings in component files are forbidden.
+6. **All spring configs come from the `springs` map.** Inline `stiffness`/`damping` values are forbidden.
+7. **`"use client"` is required** on every file that imports from `motion/react`.
+8. **Never read `window` or `navigator` at module level.** Always guard with `typeof window !== "undefined"`.
+
+## Decision Guidance
+
+### Choosing a duration
+
+| Token | Use when |
+| --------- | -------------------------------------------- |
+| `instant` | Tooltip show/hide, focus ring, badge update |
+| `fast` | Button feedback, icon swap, chip toggle |
+| `normal` | Modal open, card expand, page element enter |
+| `slow` | Hero entrance, full-page transition |
+| `crawl` | Deliberate storytelling; use sparingly |
+
+### Choosing a spring
+
+| Preset | Use when |
+| --------- | ------------------------------------------ |
+| `snappy` | Default UI — buttons, chips, nav items |
+| `gentle` | Cards, modals, panels landing softly |
+| `bouncy` | Playful moments — empty states, onboarding |
+| `instant` | Tooltips, popovers, dropdowns |
+| `release` | Drag release — natural physics feel |
+
+### When to disable animation entirely
+
+Disable (set `shouldAnimate = false`) when:
+
+- `prefersReduced` is `true`
+- `isLowEnd` is `true` and the animation is non-essential
+- The element is off-screen and will never enter the viewport
+- The animation is purely decorative with no UX purpose
+
+## Core Concepts
+
+### Token system
+
+```ts
+// lib/motion-tokens.ts
+export const motionTokens = {
+  duration: {
+    instant: 0.08,
+    fast:    0.18,
+    normal:  0.35,
+    slow:    0.6,
+    crawl:   1.0,
+  },
+  easing: {
+    smooth: [0.22, 1, 0.36, 1],
+    sharp:  [0.4, 0, 0.2, 1],
+    bounce: [0.34, 1.56, 0.64, 1],
+    linear: [0, 0, 1, 1],
+  },
+  distance: {
+    xs: 4,
+    sm: 8,
+    md: 16,
+    lg: 24,
+    xl: 48,
+  },
+  scale: {
+    subtle: 0.98,
+    press:  0.95,
+    pop:    1.04,
+  },
+}
+
+export const springs = {
+  snappy:  { type: "spring", stiffness: 300, damping: 30 },
+  gentle:  { type: "spring", stiffness: 120, damping: 14 },
+  bouncy:  { type: "spring", stiffness: 400, damping: 10 },
+  instant: { type: "spring", stiffness: 600, damping: 35 },
+  release: { type: "spring", stiffness: 200, damping: 20, restDelta: 0.001 },
+}
+```
+
+### Runtime flags
+
+```ts
+// lib/motion-config.ts
+export const motionConfig = {
+  isLowEnd:
+    typeof navigator !== "undefined" &&
+    navigator.hardwareConcurrency <= 4,
+
+  prefersReduced:
+    typeof window !== "undefined" &&
+    window.matchMedia("(prefers-reduced-motion: reduce)").matches,
+
+  get shouldAnimate() {
+    return !this.prefersReduced
+  },
+
+  get duration() {
+    return this.isLowEnd || this.prefersReduced
+      ? motionTokens.duration.instant
+      : motionTokens.duration.normal
+  },
+}
+```
+
+### Accessibility
+
+**Priority order (highest to lowest):**
+
+1. `prefers-reduced-motion: reduce` — disables all transforms, limits opacity transitions to ≤ 0.2s
+2. Low-end device detection — reduces duration, removes non-essential animations
+3. Design preference — everything else
+
+Motion must degrade gracefully. It must never disappear abruptly in a way
+that causes layout shift or confuses orientation.
+
+```tsx
+// hooks/use-reduced-motion.tsx
+"use client"
+import { useReducedMotion } from "motion/react"
+
+export function useSafeMotion(fullY: number = 16) {
+  const reduce = useReducedMotion()
+  return {
+    initial: { opacity: 0, y: reduce ? 0 : fullY },
+    animate: { opacity: 1, y: 0 },
+    exit:    { opacity: 0, y: reduce ? 0 : -fullY },
+  }
+}
+```
+
+```css
+/* globals.css */
+@media (prefers-reduced-motion: reduce) {
+  .motion-safe-transition  { transition: opacity 0.15s; }
+  .motion-reduce-transform { transform: none !important; }
+}
+```
+
+```html
+<!-- Tailwind -->
+<div class="motion-safe:animate-fade motion-reduce:opacity-100"></div>
+```
+
+### SSR / hydration safety
+
+**Rule: `initial` must always match what the server renders.**
+
+```tsx
+// WRONG — server renders opacity:1 but initial says 0 → hydration mismatch
+<motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} />
+
+// CORRECT — use AnimatePresence or defer to client mount
+"use client"
+const [mounted, setMounted] = useState(false)
+useEffect(() => setMounted(true), [])
+
+<motion.div
+  initial={{ opacity: mounted ? 0 : 1 }}
+  animate={{ opacity: 1 }}
+/>
+```
+
+## Code Examples
+
+### End-to-end: tokens + springs + accessibility + SSR guard
+
+```tsx
+// components/fade-in-card.tsx
+"use client"
+
+import { useState, useEffect } from "react"
+import { motion } from "motion/react"
+import { motionTokens, springs } from "@/lib/motion-tokens"
+import { useSafeMotion } from "@/hooks/use-reduced-motion"
+import { motionConfig } from "@/lib/motion-config"
+
+interface FadeInCardProps {
+  children: React.ReactNode
+  delay?: number
+}
+
+export function FadeInCard({ children, delay = 0 }: FadeInCardProps) {
+  // SSR guard — initial must match server output (opacity: 1)
+  const [mounted, setMounted] = useState(false)
+  useEffect(() => setMounted(true), [])
+
+  // Accessibility — disables transform when reduced motion is preferred
+  const safeMotion = useSafeMotion(motionTokens.distance.md)
+
+  // Device gate — skip animation on low-end hardware
+  if (!motionConfig.shouldAnimate || !mounted) {
+    return <div>{children}</div>
+  }
+
+  return (
+    <motion.div
+      initial={safeMotion.initial}
+      animate={safeMotion.animate}
+      exit={safeMotion.exit}
+      transition={{
+        ...springs.gentle,
+        delay,
+      }}
+      whileHover={{ scale: motionTokens.scale.pop }}
+      whileTap={{ scale: motionTokens.scale.press }}
+    >
+      {children}
+    </motion.div>
+  )
+}
+```
+
+## Constraints / Non-Goals
+
+This skill does **not** cover:
+
+- UI component patterns (button, modal, stagger) → see `motion-patterns`
+- Drag, gestures, SVG, text animations, custom hooks → see `motion-advanced`
+- CSS-only animations or Tailwind `animate-*` classes without `motion/react`
+- Third-party animation libraries (GSAP, anime.js, etc.)
+- Motion design decisions (when to animate, what to emphasize) — that is a design concern, not a code constraint
+
+## Anti-Patterns
+
+| Anti-pattern | Rule violated | Fix |
+| --------------------------------------- | ------- | ------------------------------- |
+| `import { motion } from "framer-motion"` | Rule 1 | Use `motion/react` |
+| `initial={{ opacity: 0 }}` on SSR component | Rule 2 | Add mount guard |
+| Skipping `useReducedMotion` check | Rule 3 | Use `useSafeMotion` hook |
+| `animate={{ width: "100%" }}` | Rule 4 | Use `scaleX` transform instead |
+| `transition={{ duration: 0.4 }}` inline | Rule 5 | Use `motionTokens.duration.normal` |
+| `{ stiffness: 300, damping: 30 }` inline | Rule 6 | Use `springs.snappy` |
+| Missing `"use client"` directive | Rule 7 | Add to top of file |
+| `navigator.hardwareConcurrency` at module level | Rule 8 | Wrap in `typeof navigator !== "undefined"` |
+
+## Related Skills
+
+- **`motion-patterns`** — consumes tokens and springs defined here to build button, modal, stagger, page transition, and scroll patterns. Does not redefine any values.
+- **`motion-advanced`** — consumes tokens and springs defined here for drag, SVG, text, and gesture patterns. Adds `useAnimate` sequences and custom hooks on top of this foundation.