> ## Documentation Index
> Fetch the complete documentation index at: https://hyperframes.heygen.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Spring Stack Shuffle

> A stack of 3 to 5 slotted cards reshuffles on cues: the back card throws over the top and lands at the front with real mass, the rest compress and resettle; cues that land mid-flight redirect the moving cards with velocity preserved.

export const InstallCommand = ({command}) => {
  const [copied, setCopied] = React.useState(false);
  const copy = async () => {
    try {
      if (navigator.clipboard && window.isSecureContext) {
        await navigator.clipboard.writeText(command);
      } else {
        const previous = document.activeElement;
        const scratch = document.createElement("textarea");
        scratch.value = command;
        scratch.setAttribute("readonly", "");
        scratch.style.position = "fixed";
        scratch.style.opacity = "0";
        document.body.appendChild(scratch);
        scratch.select();
        document.execCommand("copy");
        document.body.removeChild(scratch);
        previous?.focus?.();
      }
      setCopied(true);
      setTimeout(() => setCopied(false), 2000);
    } catch {}
  };
  return <div className="hf-install-command not-prose my-4 flex items-stretch overflow-hidden rounded-xl border border-zinc-200 bg-zinc-50 dark:border-zinc-800 dark:bg-zinc-900">
      <code className="flex-1 overflow-x-auto whitespace-nowrap border-r border-zinc-200 px-4 py-3 font-mono text-sm text-zinc-800 dark:border-zinc-800 dark:text-zinc-100">
        {command}
      </code>
      <button type="button" onClick={copy} data-copied={copied ? "true" : "false"} aria-label={`Copy ${command} to the clipboard`} className="hf-install-copy">
        <svg className="hf-install-copy-clipboard" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 18 18" fill="none" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
          <path d="M14.25 5.25H7.25C6.14543 5.25 5.25 6.14543 5.25 7.25V14.25C5.25 15.3546 6.14543 16.25 7.25 16.25H14.25C15.3546 16.25 16.25 15.3546 16.25 14.25V7.25C16.25 6.14543 15.3546 5.25 14.25 5.25Z" />
          <path d="M2.80103 11.998L1.77203 5.07397C1.61003 3.98097 2.36403 2.96397 3.45603 2.80197L10.38 1.77297C11.313 1.63397 12.19 2.16297 12.528 3.00097" />
        </svg>
        <svg className="hf-install-copy-check" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 18 18" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
          <path d="M2.75 9.5L6.5 13.25L15.25 4.5" />
        </svg>
      </button>
      <span className="hf-install-copy-status" role="status" aria-live="polite">
        {copied ? "Copied" : ""}
      </span>
    </div>;
};

<iframe className="w-full aspect-video rounded-xl border-0 bg-zinc-100 dark:bg-zinc-800" title="spring-stack-shuffle preview" loading="lazy" srcDoc={`<!doctype html><html><head><meta charset="utf-8"><style>html,body{margin:0;height:100%;overflow:hidden;background:transparent}hyperframes-player{display:block;width:100%;height:100%}</style><script src="https://cdn.jsdelivr.net/npm/@hyperframes/player@0.7/dist/hyperframes-player.global.js"><\/script></head><body><script>fetch("/public/catalog/components/spring-stack-shuffle.json").then(function(r){return r.json()}).then(function(d){var p=document.createElement("hyperframes-player");p.setAttribute("srcdoc",d.html);p.setAttribute("controls","");p.setAttribute("autoplay","");p.setAttribute("loop","");p.setAttribute("muted","");p.setAttribute("poster","https://static.heygen.ai/hyperframes-oss/docs/images/catalog/components/spring-stack-shuffle.png");document.body.appendChild(p)});<\/script></body></html>`} />

## Install

<InstallCommand command="npx hyperframes add spring-stack-shuffle" />

That writes one file: `compositions/components/spring-stack-shuffle.html`.

## Paste it into your composition

Open `compositions/components/spring-stack-shuffle.html` and copy what is inside into your own composition.

A component has no size or duration of its own. It takes both from the composition
you paste it into.

## Variables

Every one of these has a default, so the piece works untouched. Set the ones you
want to change on the element:

| Variable | Default          | Accepts                   | What it does                                                                                                                                                                                  |
| -------- | ---------------- | ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `cards`  | `4`              | 3 to 5, step 1            | Number of cards in the stack, 3 to 5.                                                                                                                                                         |
| `cues`   | `0.9, 1.7, 1.95` | string                    | Comma-separated seconds from mount start; each cue throws the back card to the front. Cues inside a running throw redirect it mid-flight, velocity preserved. Empty keeps the default rhythm. |
| `accent` | `green`          | `green`, `blue`, `violet` | Active-card ring color from the contract token map.                                                                                                                                           |
| `exit`   | `none`           | `none`, `fade`, `up`      | Optional departure. Default none: the settled stack holds until the frame cuts.                                                                                                               |

Set them with `data-variable-values` on the element that mounts it. These are the
defaults, so this behaves exactly like the preview above until you change one:

```html wrap theme={null}
<div
  data-composition-id="spring-stack-shuffle"
  data-composition-src="compositions/components/spring-stack-shuffle.html"
  data-variable-values='{"cards":4,"cues":"0.9, 1.7, 1.95","accent":"green","exit":"none"}'
></div>
```

## Source

<Accordion title={`spring-stack-shuffle.html`}>
  ```html theme={null}
  <!doctype html>
  <!--
    spring-stack-shuffle: HyperFrames video primitive (product demo / physics)

    A stack of 3 to 5 cards reshuffles on cues: on each cue the card at the
    back of the stack throws over the top and lands at the front with real
    mass (small landing overshoot, the quiet register), while the other cards
    step one slot deeper and give a brief compress-resettle as the flyer
    lands.

    SIGNATURE (law L1, interruptible springs): when a cue fires while a
    previous shuffle is still in flight, every in-flight card REDIRECTS to
    its new slot preserving its instantaneous velocity. No snap-to-zero, no
    pop. The default cue rhythm (0.9, 1.7, 1.95) deliberately fires the third
    cue mid-throw of the second so the redirect is part of the authored
    choreography.

    How the redirect stays deterministic and seek-safe: motion is compiled
    at mount into per-card, per-property segment lists (explicit from/to and
    a pure ease function each). A redirect cuts the covering segment
    analytically (value from the ease, velocity from a fixed finite
    difference), truncates it with a renormalized copy of the same curve, and
    continues with a cubic Hermite ease whose start slope equals the cut
    velocity and whose end slope is zero. Nothing simulates: every emitted
    tween is a fromTo with both endpoints authored, so any seek in either
    direction reproduces the same frame.

    Slots (see README.md for a worked example):
      - [data-slot="card-1"] ... [data-slot="card-5"]: card bodies, front to
        back at mount. Replace the children of a slot in your installed copy.
        Defaults: numbered token skeleton cards. Direct img/video children
        cover the card area.

    Variables (declared in data-composition-variables below):
      - cards (number 3..5, default 4): how many cards are in the stack.
      - cues (string, default "0.9, 1.7, 1.95"): comma-separated seconds,
        relative to mount start; each cue fires one shuffle. Cues closer
        together than a throw (0.85s) interrupt the flight and exercise the
        L1 redirect. Empty keeps the authored default rhythm.
      - accent (green | blue | violet, default green): active-card ring via
        the contract token map.
      - exit (none | fade | up, default none): frame roots own transitions;
        holds end films.

    Envelope, fixed IN and OUT with elastic HOLD only (never time-scaled):
      IN    = staggered card entrances, back to front, done by ~0.8s
      CUES  = clamped into [0.85, D - OUT - 0.9] so every throw lands before
              any exit begins
      HOLD  = still after the last landing bump settles
      OUT   = 0s for exit none, otherwise 0.45s

    Mount contract: MOUNTABLE SUB-COMPOSITION. The runtime clones only
    <template> contents; #root fills the host box (inset:0, container-type:
    size), has no data-width/data-height, and registers one paused timeline
    under the literal "spring-stack-shuffle" key. Stack geometry is measured
    in px from the mounted root once (cq-unit transform tweens are not
    seek-safe); variables come from window.__hyperframes.getVariables().
  -->
  <html
    lang="en"
    data-composition-id="spring-stack-shuffle"
    data-composition-duration="4"
    data-composition-variables='[
      { "id": "cards", "type": "number", "role": "content", "label": "Cards", "description": "Number of cards in the stack, 3 to 5.", "default": 4, "min": 3, "max": 5, "step": 1 },
      { "id": "cues", "type": "string", "role": "timing", "label": "Shuffle cues", "description": "Comma-separated seconds from mount start; each cue throws the back card to the front. Cues inside a running throw redirect it mid-flight, velocity preserved. Empty keeps the default rhythm.", "default": "0.9, 1.7, 1.95" },
      { "id": "accent", "type": "enum", "role": "style", "label": "Accent", "description": "Active-card ring color from the contract token map.", "default": "green", "options": [{ "value": "green", "label": "Green" }, { "value": "blue", "label": "Blue" }, { "value": "violet", "label": "Violet" }] },
      { "id": "exit", "type": "enum", "role": "timing", "label": "Exit", "description": "Optional departure. Default none: the settled stack holds until the frame cuts.", "default": "none", "options": [{ "value": "none", "label": "None" }, { "value": "fade", "label": "Fade" }, { "value": "up", "label": "Up" }] }
    ]'
  >
    <head>
      <meta charset="UTF-8" />
      <title>Spring Stack Shuffle</title>
    </head>
    <body>
      <template>
        <div id="root" data-composition-id="spring-stack-shuffle" data-duration="4" data-fps="30">
          <style>
            *,
            *::before,
            *::after {
              box-sizing: border-box;
            }

            #root {
              position: absolute;
              inset: 0;
              overflow: hidden;
              container-type: size;
              isolation: isolate;
              background: var(--bg, #0b0c0e);
              color: var(--fg, #f8fafc);
              font-family: var(--font-body, Inter, system-ui, sans-serif);
              pointer-events: none;
            }

            .sss-clip {
              position: absolute;
              inset: 0;
              overflow: hidden;
            }

            .sss-stage {
              position: absolute;
              inset: 0;
              will-change: transform, opacity;
            }

            .sss-card {
              position: absolute;
              left: 50%;
              top: 58%;
              width: 46cqw;
              height: 42cqh;
              margin-left: -23cqw;
              margin-top: -21cqh;
              border: 0.16cqmin solid var(--border, #343a46);
              border-radius: var(--radius, 2.2cqmin);
              background: var(--surface, #14171c);
              box-shadow: 0 2.2cqh 6cqh color-mix(in srgb, var(--bg, #000000) 55%, transparent);
              overflow: hidden;
              will-change: transform, opacity;
            }

            /* Active-card ring: opacity is timeline-driven so the front card
               reads as the live one across every shuffle. */
            .sss-ring {
              position: absolute;
              inset: 0;
              border: 0.4cqmin solid var(--sss-accent, #71f5a7);
              border-radius: inherit;
              opacity: 0;
              pointer-events: none;
              z-index: 3;
            }

            /* Depth veil: timeline-driven dim; deeper cards sit darker. */
            .sss-veil {
              position: absolute;
              inset: 0;
              background: var(--bg, #0b0c0e);
              border-radius: inherit;
              opacity: 0;
              pointer-events: none;
              z-index: 2;
            }

            .sss-slot {
              position: absolute;
              inset: 0;
              overflow: hidden;
              border-radius: inherit;
            }

            .sss-slot > img,
            .sss-slot > video {
              width: 100%;
              height: 100%;
              object-fit: cover;
            }

            .sss-default {
              position: absolute;
              inset: 0;
              padding: var(--space-3, 3.2cqmin);
              display: flex;
              flex-direction: column;
              gap: var(--space-2, 2cqmin);
            }

            .sss-chip {
              align-self: flex-start;
              padding: 0.9cqmin 1.8cqmin;
              border: 0.14cqmin solid var(--border, #343a46);
              border-radius: 999cqmin;
              color: var(--muted, #94a3b8);
              font-family: var(--font-mono, ui-monospace, "SF Mono", Menlo, Consolas, monospace);
              font-size: min(1.7cqw, 3cqh);
              font-weight: 600;
              letter-spacing: 0.08em;
              line-height: 1;
            }

            .sss-bar {
              width: 46%;
              height: 8%;
              border-radius: 999cqmin;
              background: color-mix(in srgb, var(--fg, #f8fafc) 22%, var(--surface, #14171c));
            }

            .sss-line {
              width: 84%;
              height: 5%;
              border-radius: 999cqmin;
              background: color-mix(in srgb, var(--muted, #94a3b8) 34%, var(--surface, #14171c));
            }

            .sss-line + .sss-line {
              width: 70%;
            }
          </style>

          <div
            id="spring-stack-shuffle-clip"
            class="sss-clip clip"
            data-start="0"
            data-duration="4"
            data-track-index="0"
          >
            <div class="sss-stage">
              <section class="sss-card" aria-label="Card 1">
                <div class="sss-slot" data-slot="card-1">
                  <!-- SLOT "card-1": replace the children of this element with
                       your own content (img, video, or HTML). -->
                  <div class="sss-default" aria-hidden="true">
                    <div class="sss-chip">01</div>
                    <div class="sss-bar"></div>
                    <div class="sss-line"></div>
                    <div class="sss-line"></div>
                  </div>
                </div>
                <div class="sss-veil"></div>
                <div class="sss-ring"></div>
              </section>
              <section class="sss-card" aria-label="Card 2">
                <div class="sss-slot" data-slot="card-2">
                  <!-- SLOT "card-2": replace the children of this element with
                       your own content (img, video, or HTML). -->
                  <div class="sss-default" aria-hidden="true">
                    <div class="sss-chip">02</div>
                    <div class="sss-bar"></div>
                    <div class="sss-line"></div>
                    <div class="sss-line"></div>
                  </div>
                </div>
                <div class="sss-veil"></div>
                <div class="sss-ring"></div>
              </section>
              <section class="sss-card" aria-label="Card 3">
                <div class="sss-slot" data-slot="card-3">
                  <!-- SLOT "card-3": replace the children of this element with
                       your own content (img, video, or HTML). -->
                  <div class="sss-default" aria-hidden="true">
                    <div class="sss-chip">03</div>
                    <div class="sss-bar"></div>
                    <div class="sss-line"></div>
                    <div class="sss-line"></div>
                  </div>
                </div>
                <div class="sss-veil"></div>
                <div class="sss-ring"></div>
              </section>
              <section class="sss-card" aria-label="Card 4">
                <div class="sss-slot" data-slot="card-4">
                  <!-- SLOT "card-4": replace the children of this element with
                       your own content (img, video, or HTML). -->
                  <div class="sss-default" aria-hidden="true">
                    <div class="sss-chip">04</div>
                    <div class="sss-bar"></div>
                    <div class="sss-line"></div>
                    <div class="sss-line"></div>
                  </div>
                </div>
                <div class="sss-veil"></div>
                <div class="sss-ring"></div>
              </section>
              <section class="sss-card" aria-label="Card 5">
                <div class="sss-slot" data-slot="card-5">
                  <!-- SLOT "card-5": replace the children of this element with
                       your own content (img, video, or HTML). -->
                  <div class="sss-default" aria-hidden="true">
                    <div class="sss-chip">05</div>
                    <div class="sss-bar"></div>
                    <div class="sss-line"></div>
                    <div class="sss-line"></div>
                  </div>
                </div>
                <div class="sss-veil"></div>
                <div class="sss-ring"></div>
              </section>
            </div>
          </div>

          <script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
          <script>
            (function () {
              "use strict";

              var root = document.getElementById("root");
              // Literal id: mount flattening strips data-composition-id from
              // the live root before this timeline registers.
              var compositionId = "spring-stack-shuffle";
              var stage = root.querySelector(".sss-stage");
              var vars =
                window.__hyperframes && window.__hyperframes.getVariables
                  ? window.__hyperframes.getVariables()
                  : {};

              var accentColors = {
                green: "var(--brand, #71f5a7)",
                blue: "var(--accent, #61a8ff)",
                violet: "var(--accent-2, #c5a3ff)",
              };
              var accent = Object.prototype.hasOwnProperty.call(accentColors, vars.accent)
                ? vars.accent
                : "green";
              root.style.setProperty("--sss-accent", accentColors[accent]);
              var exit = vars.exit === "fade" || vars.exit === "up" ? vars.exit : "none";

              var cardCountRaw = Number(vars.cards);
              var cardCount = Number.isFinite(cardCountRaw)
                ? Math.max(3, Math.min(5, Math.round(cardCountRaw)))
                : 4;
              var cardEls = Array.prototype.slice.call(root.querySelectorAll(".sss-card"));
              cardEls.slice(cardCount).forEach(function (el) {
                el.remove();
              });
              cardEls = cardEls.slice(0, cardCount);

              // Stack geometry in px measured once from the mounted root:
              // cq-unit transform tweens are not seek-safe, px numbers are.
              var rect = root.getBoundingClientRect();
              var W = Math.max(1, rect.width);
              var H = Math.max(1, rect.height);
              var STEP_Y = -0.055 * H; // deeper cards peek above the front card
              var STEP_S = 0.05;
              var APEX_Y = STEP_Y * (cardCount - 1) - 0.09 * H; // arc above the stack
              var KICK_X = 0.12 * W; // lateral kick during the throw
              var BUMP_Y = 0.012 * H; // stack compress as the flyer lands

              function poseFor(depth) {
                return {
                  y: depth * STEP_Y,
                  s: 1 - depth * STEP_S,
                  veil: Math.min(0.5, depth * 0.15),
                };
              }

              // RETIME RANGE: fixed IN and OUT; HOLD is the only elastic span.
              var THROW = 0.85;
              var RISE = THROW * 0.4;
              var LAND = THROW * 0.6;
              var SHIFT = 0.55;
              var OUT = exit === "none" ? 0 : 0.45;
              var duration = Math.max(0.001, parseFloat(root.dataset.duration || "4"));
              var OUT_START = duration - OUT;
              var CUE_MIN = 0.85;
              var CUE_MAX = Math.max(CUE_MIN, OUT_START - THROW - 0.05);

              var cues = String(
                vars.cues == null || String(vars.cues).trim() === "" ? "0.9, 1.7, 1.95" : vars.cues,
              )
                .split(",")
                .map(function (token) {
                  return Number(token);
                })
                .filter(function (value) {
                  return Number.isFinite(value);
                })
                .map(function (value) {
                  return Math.min(CUE_MAX, Math.max(CUE_MIN, value));
                })
                .sort(function (a, b) {
                  return a - b;
                });

              /* Author-time motion compiler. A track is one (element, property)
                 pair holding non-overlapping segments; every segment is a pure
                 curve with explicit endpoints. cutAt() is the L1 primitive: it
                 evaluates value and velocity at the cut analytically, truncates
                 the covering segment to a renormalized copy of its own curve,
                 and drops everything later. redirect() continues from the cut
                 with a Hermite ease whose start slope IS the cut velocity. */
              function easeFn(ease) {
                return typeof ease === "function" ? ease : gsap.parseEase(ease);
              }

              function makeTrack(el, prop, initial) {
                return { el: el, prop: prop, initial: initial, segs: [] };
              }

              function endValue(track) {
                return track.segs.length > 0 ? track.segs[track.segs.length - 1].to : track.initial;
              }

              function cutAt(track, time) {
                var segs = track.segs;
                while (segs.length > 0 && segs[segs.length - 1].t0 >= time) segs.pop();
                if (segs.length === 0) return { value: track.initial, velocity: 0 };
                var last = segs[segs.length - 1];
                if (last.t1 <= time) return { value: last.to, velocity: 0 };
                var curve = easeFn(last.ease);
                var span = last.t1 - last.t0;
                var f = (time - last.t0) / span;
                var lo = Math.max(0, f - 0.001);
                var hi = Math.min(1, f + 0.001);
                var slope = (curve(hi) - curve(lo)) / (hi - lo);
                var progress = curve(f);
                var value = last.from + (last.to - last.from) * progress;
                var velocity = ((last.to - last.from) * slope) / span;
                last.t1 = time;
                last.to = value;
                if (progress > 1e-6) {
                  last.ease = (function (fullCurve, cutFraction, cutProgress) {
                    return function (u) {
                      return fullCurve(u * cutFraction) / cutProgress;
                    };
                  })(curve, f, progress);
                }
                return { value: value, velocity: velocity };
              }

              // Cubic Hermite: h(0)=0, h(1)=1, h'(0)=m, h'(1)=0. A hot start
              // slope overshoots past the target and eases back, which is the
              // spring read; the clamp keeps it in the quiet register (L2).
              function hermite(m0) {
                var m = Math.max(-4, Math.min(4, m0));
                return function (u) {
                  return u * u * u * (m - 2) + u * u * (3 - 2 * m) + m * u;
                };
              }

              var smooth = hermite(0); // smoothstep: zero slope both ends

              // Landing ease: zero-slope start (ballistic hang at the apex),
              // small overshoot past the target, zero-slope settle. C1 all the
              // way through, pure function of progress.
              function landEase(overshoot) {
                return function (u) {
                  if (u < 0.62) {
                    var a = u / 0.62;
                    return (1 + overshoot) * a * a * (3 - 2 * a);
                  }
                  var b = (u - 0.62) / 0.38;
                  return 1 + overshoot - overshoot * b * b * (3 - 2 * b);
                };
              }

              function addSeg(track, t0, dur, to, ease) {
                track.segs.push({ t0: t0, t1: t0 + dur, from: endValue(track), to: to, ease: ease });
              }

              function redirect(track, time, dur, to) {
                var cut = cutAt(track, time);
                var delta = to - cut.value;
                var ease = Math.abs(delta) < 1e-4 ? smooth : hermite((cut.velocity * dur) / delta);
                track.segs.push({ t0: time, t1: time + dur, from: cut.value, to: to, ease: ease });
              }

              var powerOut = gsap.parseEase("power3.out");
              var cards = cardEls.map(function (el, index) {
                var pose = poseFor(index);
                return {
                  el: el,
                  depth: index,
                  landing: null,
                  x: makeTrack(el, "x", 0),
                  y: makeTrack(el, "y", pose.y + 0.05 * H),
                  s: makeTrack(el, "s", pose.s * 0.985),
                  veil: makeTrack(el.querySelector(".sss-veil"), "veil", pose.veil),
                  ring: makeTrack(el.querySelector(".sss-ring"), "ring", 0),
                };
              });
              var zEvents = [];

              // IN: staggered entrances, back card first, front card last.
              cards.forEach(function (card, index) {
                var pose = poseFor(index);
                var tIn = (cardCount - 1 - index) * 0.07;
                addSeg(card.y, tIn, 0.5, pose.y, powerOut);
                addSeg(card.s, tIn, 0.5, pose.s, powerOut);
                if (index === 0) addSeg(card.ring, 0.45, 0.3, 0.9, smooth);
              });

              // SHUFFLES: one per cue. The back card throws over the top; the
              // rest step one slot deeper. Any card still in flight when a cue
              // fires is cut and redirected, velocity preserved (L1).
              cues.forEach(function (cue) {
                var back = cards.reduce(function (a, b) {
                  return b.depth > a.depth ? b : a;
                });
                cards.forEach(function (card) {
                  if (card.landing && card.landing.t > cue) card.landing.canceled = true;
                  card.landing = null;
                  card.depth = card === back ? 0 : card.depth + 1;
                  zEvents.push({
                    t: cue,
                    el: card.el,
                    z: card === back ? 60 : 40 - card.depth,
                    canceled: false,
                  });
                });

                cards.forEach(function (card) {
                  var pose = poseFor(card.depth);
                  if (card === back) {
                    // Throw arc: velocity-matched rise to a ballistic apex,
                    // then a landing with one small sanctioned overshoot.
                    redirect(card.x, cue, RISE, KICK_X);
                    addSeg(card.x, cue + RISE, LAND, 0, smooth);
                    redirect(card.y, cue, RISE, APEX_Y);
                    addSeg(card.y, cue + RISE, LAND, pose.y, landEase(0.06));
                    redirect(card.s, cue, RISE, 1.05);
                    addSeg(card.s, cue + RISE, LAND, pose.s, landEase(0.04));
                    redirect(card.veil, cue, THROW, pose.veil);
                    redirect(card.ring, cue, THROW, 0.9);
                    var landing = { t: cue + THROW, el: card.el, z: 40, canceled: false };
                    zEvents.push(landing);
                    card.landing = landing;
                  } else {
                    redirect(card.x, cue, SHIFT, 0);
                    redirect(card.y, cue, SHIFT, pose.y);
                    redirect(card.s, cue, SHIFT, pose.s);
                    redirect(card.veil, cue, SHIFT, pose.veil);
                    redirect(card.ring, cue, SHIFT, 0);
                  }
                });

                // Compress-resettle: the stack takes the flyer's weight.
                cards.forEach(function (card) {
                  if (card === back) return;
                  var rest = endValue(card.y);
                  addSeg(card.y, cue + THROW - 0.05, 0.16, rest + BUMP_Y, smooth);
                  addSeg(card.y, cue + THROW + 0.11, 0.22, rest, smooth);
                });
              });

              // EMIT: initial states, then every compiled segment as an
              // explicit fromTo. Segments never overlap per track, both
              // endpoints are authored, eases are pure functions: seek-safe.
              var propFor = {
                x: function (value) {
                  return { x: value };
                },
                y: function (value) {
                  return { y: value };
                },
                s: function (value) {
                  return { scale: value };
                },
                veil: function (value) {
                  return { opacity: value };
                },
                ring: function (value) {
                  return { opacity: value };
                },
              };

              gsap.set(stage, { opacity: 1, y: 0 });
              cards.forEach(function (card, index) {
                gsap.set(card.el, { opacity: 0, zIndex: 40 - index });
              });

              var tl = gsap.timeline({ paused: true });

              cards.forEach(function (card, index) {
                var tIn = (cardCount - 1 - index) * 0.07;
                tl.fromTo(
                  card.el,
                  { opacity: 0 },
                  { opacity: 1, duration: 0.4, ease: "power2.out" },
                  tIn,
                );
                ["x", "y", "s", "veil", "ring"].forEach(function (prop) {
                  var track = card[prop];
                  var toProps = propFor[prop];
                  gsap.set(track.el, toProps(track.initial));
                  track.segs.forEach(function (seg) {
                    var dur = seg.t1 - seg.t0;
                    if (dur < 1 / 120) {
                      tl.set(track.el, toProps(seg.to), seg.t1);
                      return;
                    }
                    var to = toProps(seg.to);
                    to.duration = dur;
                    to.ease = easeFn(seg.ease);
                    tl.fromTo(track.el, toProps(seg.from), to, seg.t0);
                  });
                });
              });

              zEvents.forEach(function (event) {
                if (event.canceled) return;
                tl.set(event.el, { zIndex: event.z }, event.t);
              });

              // HOLD: completely still after the last landing bump.

              // OUT: optional departure; exit none holds until the frame cuts.
              if (exit === "fade") {
                tl.to(stage, { opacity: 0, duration: OUT, ease: "power2.in" }, OUT_START);
              } else if (exit === "up") {
                tl.to(
                  stage,
                  { opacity: 0, y: -0.07 * H, duration: OUT, ease: "power2.in" },
                  OUT_START,
                );
              }

              tl.seek(0);
              window.__timelines = window.__timelines || {};
              window.__timelines[compositionId] = tl;
            })();
          </script>
        </div>
      </template>
    </body>
  </html>
  ```
</Accordion>

Tagged `motion-primitive` `product-demo` `physics` `stack` `interruptible-spring`.

## Related topics

* [Browse the complete Catalog](/catalog)
* [Add assets and Catalog items in Studio](/studio/assets-and-blocks)
* [Build a richer composition](/go-further)


## Related topics

- [Spring Pop](/catalog/components/spring-pop.md)
- [Notification Stack](/catalog/components/notification-stack.md)
- [Keyframe Scrub Stack](/catalog/components/keyframe-scrub-stack.md)
