Skeleton Reveal

<!--
  Skeleton Reveal - transitions.dev-inspired primitive for HyperFrames.

  Paste the markup and CSS into a composition. Use the timeline integration
  note at the bottom as the starting point for deterministic GSAP animation.

  Variables. The script reads each one, falls back to the declared default on
  anything missing or invalid, and writes the result as a custom property the
  CSS below consumes, or straight onto the revealed text. The timeline recipe
  stays untouched: it keeps sweeping the skeleton and cross-fading to the
  content, and these decide what that content says and what both halves look
  like.

    - name (string, default Jane Cooper): the primary line revealed once the
      skeleton fades out. Blank falls back to the default.
    - detail (string, default jane@example.com): the secondary line under the
      name, such as an email or a role. Blank falls back to the default.
    - tone (light | dark, default light): card palette. Light is the paper card
      with grey bars, dark is a near-black card with the matching skeleton bars
      and text, for compositions on a dark stage.

  On every default the result is identical to the original: a white card that
  shimmers, then reveals Jane Cooper and jane@example.com.
-->

<div
  class="hf-transition-skeleton-reveal"
  data-composition-variables='[
    { "id": "name", "type": "string", "role": "content", "label": "Name", "description": "Primary line revealed once the skeleton fades out.", "default": "Jane Cooper" },
    { "id": "detail", "type": "string", "role": "content", "label": "Detail", "description": "Secondary line under the name, such as an email or a role.", "default": "jane@example.com" },
    { "id": "tone", "type": "enum", "role": "style", "label": "Tone", "description": "Card palette. Light is the paper card, dark is a near-black card with the matching skeleton bars and text.", "default": "light", "options": [{ "value": "light", "label": "Light" }, { "value": "dark", "label": "Dark" }] }
  ]'
>
  <div class="skeleton"></div>
  <div class="content"><strong>Jane Cooper</strong><span>jane@example.com</span></div>
</div>

<style>
  .hf-transition-skeleton-reveal {
    position: relative;
    width: 340px;
    height: 76px;
    font-family: Inter, system-ui, sans-serif;
  }
  .hf-transition-skeleton-reveal .skeleton,
  .hf-transition-skeleton-reveal .content {
    position: absolute;
    inset: 0;
    border: 1px solid var(--hf-sr-border, #e4e4e7);
    border-radius: 14px;
    background: var(--hf-sr-surface, #fff);
  }
  .hf-transition-skeleton-reveal .skeleton {
    background: linear-gradient(
      90deg,
      var(--hf-sr-bar, #f4f4f5),
      var(--hf-sr-bar-strong, #e4e4e7),
      var(--hf-sr-bar, #f4f4f5)
    );
    background-size: 240% 100%;
    opacity: 1;
  }
  .hf-transition-skeleton-reveal .content {
    display: grid;
    align-content: center;
    gap: 5px;
    padding: 15px;
    opacity: 0;
    color: var(--hf-sr-ink, #18181b);
  }
  .hf-transition-skeleton-reveal span {
    color: var(--hf-sr-muted, #71717a);
    font-size: 14px;
  }
</style>

<script>
  (function () {
    "use strict";

    var vars =
      window.__hyperframes && window.__hyperframes.getVariables
        ? window.__hyperframes.getVariables()
        : {};

    // Unrecognised overrides return to their declared defaults.
    var tones = {
      light: null,
      dark: {
        "--hf-sr-surface": "#18181b",
        "--hf-sr-border": "#27272a",
        "--hf-sr-bar": "#27272a",
        "--hf-sr-bar-strong": "#3f3f46",
        "--hf-sr-ink": "#fafafa",
        "--hf-sr-muted": "#a1a1aa",
      },
    };
    var defaultName = "Jane Cooper";
    var defaultDetail = "jane@example.com";

    function pick(table, value, fallback) {
      return Object.prototype.hasOwnProperty.call(table, value) ? value : fallback;
    }

    function text(value, fallback) {
      return typeof value === "string" && value.trim() ? value.trim() : fallback;
    }

    var tone = tones[pick(tones, vars.tone, "light")];
    var name = text(vars.name, defaultName);
    var detail = text(vars.detail, defaultDetail);

    var roots = document.querySelectorAll(".hf-transition-skeleton-reveal");
    for (var i = 0; i < roots.length; i += 1) {
      var root = roots[i];
      if (tone) {
        for (var key in tone) root.style.setProperty(key, tone[key]);
      }
      var strong = root.querySelector(".content strong");
      var span = root.querySelector(".content span");
      if (strong) strong.textContent = name;
      if (span) span.textContent = detail;
    }
  })();
</script>

<!--
  Timeline integration:
  tl.to('.hf-transition-skeleton-reveal .skeleton', { backgroundPosition: '100% 0', duration: 0.7, ease: 'none' }, startTime); tl.to('.hf-transition-skeleton-reveal .skeleton', { opacity: 0, duration: 0.22 }, startTime + 0.72); tl.to('.hf-transition-skeleton-reveal .content', { opacity: 1, duration: 0.24 }, startTime + 0.78);
-->