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fixing-motion-performance

Skill3 starsChanged 5 months agoMITView on GitHub

Audit and fix animation performance issues including layout thrashing, compositor properties, scroll-linked motion, and blur effects. Use when animations stutter, transitions jank, or reviewing CSS/JS animation performance.

We split this skill into the rules it gives an agent

32 rules. 18 are common, 14 are distinctive, and 0 are very specific to this project.

  • 18

    Common

    Most of the 7 edited versions we read keep these.

  • 14

    Distinctive

    This author's own choices. Worth a look.

  • 0

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Common:

    Do not migrate animation libraries unless explicitly requested.

    line 21
  2. Common:

    do not interleave layout reads and writes in the same frame

    line 56
  3. Common:

    do not animate layout continuously on large or meaningful surfaces

    line 57
  4. Common:

    do not drive animation from scrollTop, scrollY, or scroll events

    line 58
  5. Distinctive:

    no requestAnimationFrame loops without a stop condition

    line 59
  6. Common:

    do not mix multiple animation systems that each measure or mutate layout

    line 60
  7. Distinctive:

    default to transform and opacity for motion

    line 64
  8. Common:

    use JS-driven animation only when interaction requires it

    line 65
  9. Common:

    prefer downgrading technique over removing motion entirely

    line 68
  10. Common:

    do not read layout repeatedly during an animation

    line 74
  11. Common:

    prefer FLIP-style transitions for layout-like effects

    line 75
  12. Distinctive:

    prefer approaches that batch measurement and writes

    line 76
  13. Distinctive:

    prefer Scroll or View Timelines for scroll-linked motion when available

    line 80
  14. Distinctive:

    use IntersectionObserver for visibility and pausing

    line 81
  15. Distinctive:

    do not poll scroll position for animation

    line 82
  16. Common:

    do not animate paint-heavy properties on large containers

    line 89
  17. Distinctive:

    do not animate CSS variables for transform, opacity, or position

    line 90
  18. Distinctive:

    do not animate inherited CSS variables

    line 91
  19. Distinctive:

    use will-change temporarily and surgically

    line 97
  20. Common:

    avoid many or large promoted layers

    line 98
  21. Distinctive:

    keep blur animation small (<=8px)

    line 103
  22. Distinctive:

    use blur only for short, one-time effects

    line 104
  23. Distinctive:

    never animate blur continuously

    line 105
  24. Common:

    never animate blur on large surfaces

    line 106
  25. Distinctive:

    prefer opacity and translate before blur

    line 107
  26. Common:

    use view transitions only for navigation-level changes

    line 111
  27. Common:

    avoid view transitions for interaction-heavy UI

    line 112
  28. Common:

    avoid view transitions when interruption or cancellation is required

    line 113
  29. Common:

    treat size changes as potentially layout-triggering

    line 114
  30. Common:

    do not migrate or rewrite animation libraries unless explicitly requested

    line 118
  31. Distinctive:

    never partially migrate APIs or mix styles within the same component

    line 120
  32. Common:

    when reviewing, prefer actionable notes and concrete alternatives over theory

    line 151

“Common” is measured: kept by at least 6 in 10 of the 7 edited versions of this file we could read. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

fixing-motion-performance

Fix animation performance issues.

how to use

  • /fixing-motion-performance Apply these constraints to any UI animation work in this conversation.
  • /fixing-motion-performance <file> Review the file against all rules below and report:
    • violations (quote the exact line or snippet)
    • why it matters (one short sentence)
    • a concrete fix (code-level suggestion)

Do not migrate animation libraries unless explicitly requested. Apply rules within the existing stack.

when to apply

Reference these guidelines when:

  • adding or changing UI animations (CSS, WAAPI, Motion, rAF, GSAP)
  • refactoring janky interactions or transitions
  • implementing scroll-linked motion or reveal-on-scroll
  • animating layout, filters, masks, gradients, or CSS variables
  • reviewing components that use will-change, transforms, or measurement

rendering steps glossary

  • composite: transform, opacity
  • paint: color, borders, gradients, masks, images, filters
  • layout: size, position, flow, grid, flex

rule categories by priority

prioritycategoryimpact
1never patternscritical
2choose the mechanismcritical
3measurementhigh
4scrollhigh
5paintmedium-high
6layersmedium
7blur and filtersmedium
8view transitionslow
9tool boundariescritical

quick reference

1. never patterns (critical)

  • do not interleave layout reads and writes in the same frame
  • do not animate layout continuously on large or meaningful surfaces
  • do not drive animation from scrollTop, scrollY, or scroll events
  • no requestAnimationFrame loops without a stop condition
  • do not mix multiple animation systems that each measure or mutate layout

2. choose the mechanism (critical)

  • default to transform and opacity for motion
  • use JS-driven animation only when interaction requires it
  • paint or layout animation is acceptable only on small, isolated surfaces
  • one-shot effects are acceptable more often than continuous motion
  • prefer downgrading technique over removing motion entirely

3. measurement (high)

  • measure once, then animate via transform or opacity
  • batch all DOM reads before writes
  • do not read layout repeatedly during an animation
  • prefer FLIP-style transitions for layout-like effects
  • prefer approaches that batch measurement and writes

4. scroll (high)

  • prefer Scroll or View Timelines for scroll-linked motion when available
  • use IntersectionObserver for visibility and pausing
  • do not poll scroll position for animation
  • pause or stop animations when off-screen
  • scroll-linked motion must not trigger continuous layout or paint on large surfaces

5. paint (medium-high)

  • paint-triggering animation is allowed only on small, isolated elements
  • do not animate paint-heavy properties on large containers
  • do not animate CSS variables for transform, opacity, or position
  • do not animate inherited CSS variables
  • scope animated CSS variables locally and avoid inheritance

6. layers (medium)

  • compositor motion requires layer promotion, never assume it
  • use will-change temporarily and surgically
  • avoid many or large promoted layers
  • validate layer behavior with tooling when performance matters

7. blur and filters (medium)

  • keep blur animation small (<=8px)
  • use blur only for short, one-time effects
  • never animate blur continuously
  • never animate blur on large surfaces
  • prefer opacity and translate before blur

8. view transitions (low)

  • use view transitions only for navigation-level changes
  • avoid view transitions for interaction-heavy UI
  • avoid view transitions when interruption or cancellation is required
  • treat size changes as potentially layout-triggering

9. tool boundaries (critical)

  • do not migrate or rewrite animation libraries unless explicitly requested
  • apply these rules within the existing animation system
  • never partially migrate APIs or mix styles within the same component

common fixes

/* layout thrashing: animate transform instead of width */
/* before */ .panel { transition: width 0.3s; }
/* after */  .panel { transition: transform 0.3s; }

/* scroll-linked: use scroll-timeline instead of JS */
/* before */ window.addEventListener('scroll', () => el.style.opacity = scrollY / 500)
/* after */  .reveal { animation: fade-in linear; animation-timeline: view(); }
// measurement: batch reads before writes (FLIP)
// before — layout thrash
el.style.left = el.getBoundingClientRect().left + 10 + 'px';
// after — measure once, animate via transform
const first = el.getBoundingClientRect();
el.classList.add('moved');
const last = el.getBoundingClientRect();
el.style.transform = `translateX(${first.left - last.left}px)`;
requestAnimationFrame(() => { el.style.transition = 'transform 0.3s'; el.style.transform = ''; });

review guidance

  • enforce critical rules first (never patterns, tool boundaries)
  • choose the least expensive rendering work that matches the intent
  • for any non-default choice, state the constraint that justifies it (surface size, duration, or interaction requirement)
  • when reviewing, prefer actionable notes and concrete alternatives over theory

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Trending

Surging: 1 new project took it in the last 4 weeks, none the 4 weeks before.thin data

Week of Aug 30: 0 new projectsWeek of Sep 6: 0 new projectsWeek of Sep 13: 0 new projectsWeek of Sep 20: 0 new projectsWeek of Sep 27: 1 new projectWeek of Oct 4: 0 new projectsWeek of Oct 11: 0 new projectsWeek of Oct 18: 0 new projects
Aug 2026Sep 2026Oct 2026
New projects taking a version of this file each week, over the 8 weeks our latest run read: only 1 in all, so this is a hint, not a trend.
  • Other versions10 projects use a version of this.

    Word for word · 3

    1. ibelick/ui-skills★ 10k100% same
    2. master5d/claude-design-skills★ 26100% same
    3. ClaireAll/skills★ 2100% same

    Edited · 5

    1. nolly-studio/cult-ui★ 6.6k98% same
    2. kapishdima/soundcn★ 86498% same
    3. kumaran-is/claude-code-onboarding★ 3522% same
    4. FelipeAngeli/skills★ 298% same
    5. sanmidable/skills★ 297% same

    Wrote their own version · 2

    1. hsynozdamar-byte/claude-skills-edited★ 4same name
    2. hebertzhu/agent-foundry★ 0same name

    How matches are found. Word for word: the exact same text. Edited: shares passages with this file (“99% same” means 99% of its five-word phrases also appear here; 10% or more counts). Their own version: similar meaning, or, weakest, the same name. We can’t tell which project had it first. Projects are counted among the 200 most-starred candidates, and mentions are links to the repository we found, up to 50 per site, so both counts are a floor.

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