gsap

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Translated

Use when you need to add or debug professional web animations with GSAP (timelines, ScrollTrigger, stagger, transforms) in HTML/CSS/JS/React. Includes patterns for smooth motion, performance, and common pitfalls.

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Sourcemengto/skills

Added on2026-02-23

NPX Install

npx skill4agent add mengto/skills gsap

SKILL.md Content

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GSAP (GreenSock) — Web Animation Skill

When to use

High-quality UI/motion design: entrances, micro-interactions, page transitions
Timeline-based sequences (vs. scattered CSS transitions)
Scroll-driven storytelling (with ScrollTrigger)
Complex easing, staggering, orchestration across many elements

Key concepts & APIs

Tweens:

```
gsap.to(targets, vars)
```
```
gsap.from(targets, vars)
```
```
gsap.fromTo(targets, fromVars, toVars)
```

Timelines:

const tl = gsap.timeline({ defaults, repeat, yoyo, paused })

Chain:

tl.to(...).from(...).addLabel('x').add(() => ...)

Position parameter: absolute
```
1.2
```
, relative
```
"+=0.5"
```
, overlap
```
"-=0.3"
```
, label
```
"intro"
```

Eases:

ease: "power2.out"

,

"expo.inOut"

,

"elastic.out(1, 0.3)"

Staggers:

stagger: 0.05

or

{ each, from: "start|center|end|random", grid }

Performance-friendly properties:
- Prefer transforms (
```
x
```
  ,
```
y
```
  ,
```
scale
```
  ,
```
rotation
```
  ) and opacity (
```
autoAlpha
```
  )

ScrollTrigger (plugin):

```
gsap.registerPlugin(ScrollTrigger)
```

Inline:

gsap.to(".box", { scrollTrigger: ".box", x: 500 })

Advanced:

scrollTrigger: { trigger, start, end, scrub, pin, snap, markers }

Standalone:

ScrollTrigger.create({ trigger, start, end, onUpdate, onToggle })

Common pitfalls (and fixes)

Animating layout properties (top/left/width/height) → jank
- Use transforms, add
```
will-change: transform
```
  , avoid forced reflow.
ScrollTrigger “not firing” due to wrong trigger sizing/overflow containers
- Ensure trigger exists, has height, and check scroll container (nested scrolling needs config).
Not cleaning up in SPA/React
- Use
```
gsap.context()
```
  and revert on unmount; kill triggers (
```
ScrollTrigger.getAll().forEach(t => t.kill())
```
  ) if needed.
FOUC / measuring before fonts/images load
- Initialize after layout is stable; run
```
ScrollTrigger.refresh()
```
  after images load.

Quick recipes

1) Hero entrance (stagger)

js

gsap.from(".hero [data-anim]", {
  y: 24,
  autoAlpha: 0,
  duration: 0.8,
  ease: "power2.out",
  stagger: 0.06,
});

2) Sequenced timeline

js

const tl = gsap.timeline({ defaults: { ease: "power2.out", duration: 0.6 } });
tl.from(".nav", { y: -20, autoAlpha: 0 })
  .from(".hero-title", { y: 30, autoAlpha: 0 }, "-=0.2")
  .from(".hero-cta", { scale: 0.95, autoAlpha: 0 }, "-=0.2");

3) Scroll-scrub pinned section

js

gsap.registerPlugin(ScrollTrigger);

gsap.timeline({
  scrollTrigger: {
    trigger: ".story",
    start: "top top",
    end: "+=800",
    scrub: 1,
    pin: true,
  },
}).to(".story .panel", { xPercent: -200 });

What to ask the user (if requirements unclear)

Is this a static site or SPA (React/Next/Vue)? Any page transitions?
Do we need scroll-driven sections (pin/scrub/snap)?
Performance constraints (mobile support, reduced motion)?