gsap-animate

# 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 }`

## Common pitfalls (and fixes)
- Animating layout properties (top/left/width/height) → jank → Use transforms
- ScrollTrigger "not firing" → Ensure trigger has height, check scroll container
- Not cleaning up in SPA/React → Use `gsap.context()` and revert on unmount
- FOUC → Initialize after layout is stable; `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 });
```

## Tips for AI Agents
- Ask whether this is a static site or SPA (React/Next/Vue) for cleanup patterns.
- Confirm if scroll-driven sections are needed (pin/scrub/snap).
- Always consider `prefers-reduced-motion` for accessibility.