gsap

# GSAP ## Single-voice craft (do NOT parallelize) Writing a GSAP animation is one coherent authoring act with a single motion sensibility — timing, easing, and choreography must come from one hand. **Do NOT fan out to sub-agents** or split a single composition across parallel workers (their easing/duration choices will clash and the motion DNA will feel incoherent). Author the whole tween/timeline yourself, in order. **Craft moves (apply in this order):** 1. **Choreograph before coding.** Name the beats (entrance → emphasis → exit), assign each a `duration` + `ease`, and decide overlaps via the position parameter (`"<"`, `">"`, `"-=0.2"`) — not manual `delay`. One timeline, readable top-to-bottom. 2. **Stay on the compositor.** Animate only `x/y/scale/rotation/autoAlpha`; never `width/height/top/left` when a transform achieves the same look. Set shared rhythm once via `gsap.defaults()` or the timeline `defaults`. 3. **Respect motion accessibility.** Wrap motion in `gsap.matchMedia()` with a `prefers-reduced-motion: reduce` branch that drops `duration` to 0 — every shipped animation, no exception. **Worked example — accessible staggered entrance with a controllable timeline:** ```javascript const tl = gsap.timeline({ paused: true, defaults: { ease: "power2.out", duration: 0.6 } }); gsap.matchMedia().add("(prefers-reduced-motion: reduce)", () => { tl.from(".card", { autoAlpha: 0, y: 24, stagger: 0.08 }); return () => tl.set(".card", { autoAlpha: 1, y: 0 }); // reduced-motion: snap, no movement }); tl.play(); ``` ### Output contract Return **runnable GSAP code** (tween or timeline) using camelCase props + transform aliases, with: every animated element accounted for, a single coherent easing/duration system, a `matchMedia` reduced-motion branch, and stored return values when playback is controlled. State which beats map to which lines. ### Verify before done 1. **API is real** — every method/property/ease used appears in this reference (or `references/effects.md`); never invent a GSAP API. If unsure it exists, say so rather than guess (no-hallucination). 2. **Compositor-safe** — no layout properties animated where a transform suffices. 3. **Reduced-motion** — a `prefers-reduced-motion` path exists and zeroes movement. 4. **Cleanup** — off-screen/disposed tweens are killed; tweens are not created before the DOM exists. ## Core Tween Methods - **gsap.to(targets, vars)** — animate from current state to `vars`. Most common. - **gsap.from(targets, vars)** — animate from `vars` to current state (entrances). - **gsap.fromTo(targets, fromVars, toVars)** — explicit start and end. - **gsap.set(targets, vars)** — apply immediately (duration 0). Always use **camelCase** property names (e.g. `backgroundColor`, `rotationX`). ## Common vars - **duration** — seconds (default 0.5). - **delay** — seconds before start. - **ease** — `"power1.out"` (default), `"power3.inOut"`, `"back.out(1.7)"`, `"elastic.out(1, 0.3)"`, `"none"`. - **stagger** — number `0.1` or object: `{ amount: 0.3, from: "center" }`, `{ each: 0.1, from: "random" }`. - **overwrite** — `false` (default), `true`, or `"auto"`. - **repeat** — number or `-1` for infinite. **yoyo** — alternates direction with repeat. - **onComplete**, **onStart**, **onUpdate** — callbacks. - **immediateRender** — default `true` for from()/fromTo(). Set `false` on later tweens targeting the same property+element to avoid overwrite. ## Transforms and CSS Prefer GSAP's **transform aliases** over raw `transform` string: | GSAP property | Equivalent | | --------------------------- | ------------------- | | `x`, `y`, `z` | translateX/Y/Z (px) | | `xPercent`, `yPercent` | translateX/Y in % | | `scale`, `scaleX`, `scaleY` | scale | | `rotation` | rotate (deg) | | `rotationX`, `rotationY` | 3D rotate | | `skewX`, `skewY` | skew | | `transformOrigin` | transform-origin | - **autoAlpha** — prefer over `opacity`. At 0: also sets `visibility: hidden`. - **CSS variables** — `"--hue": 180`. - **svgOrigin** _(SVG only)_ — global SVG coordinate space origin. Don't combine with `transformOrigin`. - **Directional rotation** — `"360_cw"`, `"-170_short"`, `"90_ccw"`. - **clearProps** — `"all"` or comma-separated; removes inline styles on complete. - **Relative values** — `"+=20"`, `"-=10"`, `"*=2"`. ## Function-Based Values ```javascript gsap.to(".item", { x: (i, target, targets) => i * 50, stagger: 0.1, }); ``` ## Easing Built-in eases: `power1`–`power4`, `back`, `bounce`, `circ`, `elastic`, `expo`, `sine`. Each has `.in`, `.out`, `.inOut`. ## Defaults ```javascript gsap.defaults({ duration: 0.6, ease: "power2.out" }); ``` ## Controlling Tweens ```javascript const tween = gsap.to(".box", { x: 100 }); tween.pause(); tween.play(); tween.reverse(); tween.kill(); tween.progress(0.5); tween.time(0.2); ``` ## gsap.matchMedia() (Responsive + Accessibility) Runs setup only when a media query matches; auto-reverts when it stops matching. ```javascript let mm = gsap.matchMedia(); mm.add( { isDesktop: "(min-width: 800px)", reduceMotion: "(prefers-reduced-motion: reduce)", }, (context) => { const { isDesktop, reduceMotion } = context.conditions; gsap.to(".box", { rotation: isDesktop ? 360 : 180, duration: reduceMotion ? 0 : 2, }); }, ); ``` --- ## Timelines ### Creating a Timeline ```javascript const tl = gsap.timeline({ defaults: { duration: 0.5, ease: "power2.out" } }); tl.to(".a", { x: 100 }).to(".b", { y: 50 }).to(".c", { opacity: 0 }); ``` ### Position Parameter Third argument controls placement: - **Absolute**: `1` — at 1s - **Relative**: `"+=0.5"` — after end; `"-=0.2"` — before end - **Label**: `"intro"`, `"intro+=0.3"` - **Alignment**: `"<"` — same start as previous; `">"` — after previous ends; `"<0.2"` — 0.2s after previous starts ```javascript tl.to(".a", { x: 100 }, 0); tl.to(".b", { y: 50 }, "<"); // same start as .a tl.to(".c", { opacity: 0 }, "<0.2"); // 0.2s after .b starts ``` ### Labels ```javascript tl.addLabel("intro", 0); tl.to(".a", { x: 100 }, "intro"); tl.addLabel("outro", "+=0.5"); tl.play("outro"); tl.tweenFromTo("intro", "outro"); ``` ### Timeline Options - **paused: true** — create paused; call `.play()` to start. - **repeat**, **yoyo** — apply to whole timeline. - **defaults** — vars merged into every child tween. ### Nesting Timelines ```javascript const master = gsap.timeline(); const child = gsap.timeline(); child.to(".a", { x: 100 }).to(".b", { y: 50 }); master.add(child, 0); ``` ### Playback Control `tl.play()`, `tl.pause()`, `tl.reverse()`, `tl.restart()`, `tl.time(2)`, `tl.progress(0.5)`, `tl.kill()`. --- ## Performance ### Prefer Transform and Opacity Animating `x`, `y`, `scale`, `rotation`, `opacity` stays on the compositor. Avoid `width`, `height`, `top`, `left` when transforms achieve the same effect. ### will-change ```css will-change: transform; ``` Only on elements that actually animate. ### gsap.quickTo() for Frequent Updates ```javascript let xTo = gsap.quickTo("#id", "x", { duration: 0.4, ease: "power3" }), yTo = gsap.quickTo("#id", "y", { duration: 0.4, ease: "power3" }); container.addEventListener("mousemove", (e) => { xTo(e.pageX); yTo(e.pageY); }); ``` ### Stagger > Many Tweens Use `stagger` instead of separate tweens with manual delays. ### Cleanup Pause or kill off-screen animations. --- ## References (loaded on demand) - **[references/effects.md](references/effects.md)** — Drop-in effects: typewriter text, audio visualizer. Read when needing ready-made effect patterns for HyperFrames. ## Best Practices - Use camelCase property names; prefer transform aliases and autoAlpha. - Prefer timelines over chaining with delay; use the position parameter. - Add labels with `addLabel()` for readable sequencing. - Pass defaults into timeline constructor. - Store tween/timeline return value when controlling playback. ## Do Not - Animate layout properties (width/height/top/left) when transforms suffice. - Use both svgOrigin and transformOrigin on the same SVG element. - Chain animations with delay when a timeline can sequence them. - Create tweens before the DOM exists. - Skip cleanup — always kill tweens when no longer needed.