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37 Curtain reveal

Motion · Landing-page structure
Curtain reveal

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motion-curtain-reveal-everything.md

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Prompt

1.1 KB 
Curtain reveal — Curtain section reveal

Build an effect of three full-screen sections stacked in the same place. Each section is a 100vh box with position: sticky; top: 0, and the z-index is smaller for each section further down. Wrap them in an outer section 300vh tall. Compute the outer progress p (0 to 1). The first section lifts 100vh upward while p goes from 0 to 0.5, and the second lifts the same way while p goes from 0.5 to 1, so the next section appears beneath it. The lifting section casts a shadow and shrinks by about 4%. Implement it with plain CSS and JavaScript only, with no library.

Do not drop:
- Keep each section at 100vh inside a 300vh wrapper; changing the heights moves the lift boundaries
- Earlier sections sit in front (smaller z-index further down); reversing that brings the next section forward and the lift disappears
- The lift follows scroll progress p, never a timer
- Under prefers-reduced-motion, stack the sections in flow and stop the lift

A working example (one self-contained HTML file): https://design-vault.pages.dev/designs/motion-curtain-reveal/demo.html

Files

demo.html

9.2 KB

/designs/motion-curtain-reveal/demo.html — One self-contained HTML file. CSS and plain JavaScript only; it fetches nothing.

Show contents 
<!doctype html>
<html lang="ja">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>37 カーテンリビール — Curtain section reveal</title>
<style>
/* dv-motion-base:start */
:root {
  --ground: #FFFFFF;
  --surface: #F3F5F8;
  --ink: #14181F;
  --muted: #5A6472;
  --accent: #1F5FA8;
  --rule: #D8DDE4;
  --accent-soft: color-mix(in srgb, var(--accent) 12%, var(--ground));
  --accent-mid: color-mix(in srgb, var(--accent) 45%, var(--ground));
  --shade: color-mix(in srgb, var(--ink) 14%, transparent);

  --font: "Zen Kaku Gothic New", "Hiragino Sans", "Noto Sans JP", "Yu Gothic", system-ui, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --t-label: 13px;
  --t-body: 16px;
  --t-lead: 20px;
  --t-h2: 32px;
  --t-h1: clamp(40px, 7vw, 72px);

  --s1: 4px;
  --s2: 8px;
  --s3: 16px;
  --s4: 24px;
  --s5: 40px;
  --s6: 64px;
  --s7: 104px;

  --radius: 12px;
  --ease: cubic-bezier(.2, .7, .2, 1);
  --dur: .7s;
  --measure: 1080px;
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--ground);
  color: var(--ink);
  font-family: var(--font);
  font-size: var(--t-body);
  line-height: 1.7;
  font-feature-settings: "palt";
  overflow-x: hidden;
}
h1, h2, h3, p, ul, ol, figure { margin: 0; padding: 0; }
ul, ol { list-style: none; }
.dv-wrap { width: min(100% - 2 * var(--s4), var(--measure)); margin-inline: auto; }
.dv-label {
  min-height: 72vh;
  display: grid;
  align-content: center;
  gap: var(--s3);
  padding-block: var(--s6);
  border-bottom: 1px solid var(--rule);
}
.dv-num { font-family: var(--mono); font-size: var(--t-lead); font-weight: 700; color: var(--accent); letter-spacing: .04em; }
.dv-name { font-size: var(--t-h1); font-weight: 700; line-height: 1.15; letter-spacing: .01em; }
.dv-ai { font-family: var(--mono); font-size: var(--t-lead); color: var(--muted); }
.dv-desc { font-size: var(--t-lead); color: var(--ink); }
.dv-hint { font-size: var(--t-label); color: var(--muted); letter-spacing: .12em; margin-top: var(--s4); }
.dv-stage { padding-block: var(--s7); }
.dv-h2 { font-size: var(--t-h2); font-weight: 700; line-height: 1.3; }
.dv-lead { font-size: var(--t-lead); color: var(--muted); }
.dv-eyebrow { font-family: var(--mono); font-size: var(--t-label); color: var(--accent); letter-spacing: .12em; text-transform: uppercase; }
.dv-card { background: var(--surface); border: 1px solid var(--rule); border-radius: var(--radius); padding: var(--s4); }
.dv-ph {
  border-radius: var(--radius);
  background: linear-gradient(135deg, var(--accent-soft), var(--accent-mid) 60%, var(--accent));
  aspect-ratio: 16 / 9;
}
.dv-ph--alt { background: linear-gradient(200deg, var(--surface), var(--accent-soft) 55%, var(--accent-mid)); }
.dv-ph--ink { background: linear-gradient(160deg, var(--ink), color-mix(in srgb, var(--ink) 55%, var(--accent))); }
.dv-end {
  min-height: 60vh;
  display: grid;
  place-items: center;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-family: var(--mono);
  font-size: var(--t-label);
  letter-spacing: .12em;
}
/* dv-motion-base:end */

/* ---- この演出だけの CSS。色は var(--…) か color-mix() のみ ---- */
.curtain-zone { position: relative; }
.curtain-sec {
  position: relative;
  height: 100vh;
  display: grid;
  align-content: center;
  padding-inline: var(--s3);
  background: var(--ground);
}
.curtain-sec:nth-child(1) { background: var(--surface); }
.curtain-sec:nth-child(2) { background: var(--accent-soft); }
.curtain-sec .dv-wrap { display: grid; gap: var(--s3); }
.curtain-sec .dv-ph { aspect-ratio: auto; height: min(28vh, 240px); }

/* 3 つの区画を同じ位置に重ね、先の区画ほど手前に出す。JS が無いときは縦に並べる。 */
.js .curtain-zone { height: 300vh; }
.js .curtain-sec {
  position: sticky;
  top: 0;
  transform: translate3d(0, calc(var(--q, 0) * -100%), 0) scale(calc(1 - var(--q, 0) * .04));
  transform-origin: 50% 0;
  /* 影は持ち上がっている途中だけ濃く、切れたら消す（--arc は 0→1→0） */
  --arc: calc(var(--q, 0) * (1 - var(--q, 0)) * 4);
  box-shadow: 0 calc(var(--arc) * 32px) calc(var(--arc) * 64px) var(--shade);
  will-change: transform;
}
.js .curtain-sec + .curtain-sec { margin-top: -100vh; }
.js .curtain-sec:nth-child(1) { z-index: 3; }
.js .curtain-sec:nth-child(2) { z-index: 2; }
.js .curtain-sec:nth-child(3) { z-index: 1; }

@media (prefers-reduced-motion: reduce) {
  .js .curtain-zone { height: auto; }
  .js .curtain-sec:nth-child(n) { position: relative; height: auto; padding-block: var(--s7); transform: none; box-shadow: none; margin-top: 0; z-index: auto; }
}
</style>
</head>
<body data-motion-number="37">
<header class="dv-label">
  <div class="dv-wrap">
    <p class="dv-num">37</p>
    <h1 class="dv-name">カーテンリビール</h1>
    <p class="dv-ai">Curtain section reveal</p>
    <p class="dv-desc">前の画面が持ち上がり次が現れる</p>
    <p class="dv-hint">SCROLL ↓</p>
  </div>
</header>

<main class="dv-stage">
  <div class="curtain-zone" data-progress="pin">
    <section class="curtain-sec">
      <div class="dv-wrap">
        <p class="dv-eyebrow">Section 01</p>
        <h2 class="dv-h2">見出しが入ります</h2>
        <p class="dv-lead">本文のダミーです。この画面が持ち上がると、次の画面が現れます。</p>
        <div class="dv-ph"></div>
      </div>
    </section>
    <section class="curtain-sec">
      <div class="dv-wrap">
        <p class="dv-eyebrow">Section 02</p>
        <h2 class="dv-h2">見出しが入ります</h2>
        <p class="dv-lead">本文のダミーです。持ち上がった画面の下から、次の区画が見えてきます。</p>
        <div class="dv-ph dv-ph--alt"></div>
      </div>
    </section>
    <section class="curtain-sec">
      <div class="dv-wrap">
        <p class="dv-eyebrow">Section 03</p>
        <h2 class="dv-h2">見出しが入ります</h2>
        <p class="dv-lead">本文のダミーです。最後の区画は、そのまま残ります。</p>
        <div class="dv-ph dv-ph--ink"></div>
      </div>
    </section>
  </div>
</main>

<footer class="dv-end">END — 37 カーテンリビール</footer>

<script>
/* dv-motion-helpers:start */
const dvReduce = matchMedia('(prefers-reduced-motion: reduce)').matches;
document.documentElement.classList.add('js');

/**
 * 画面に入った要素へ .is-in を付ける。
 * data-reveal="repeat" の要素は画面を出たら外す（何度でも再生）。
 */
function dvReveal(selector = '[data-reveal]', { threshold = 0.2, rootMargin = '0px 0px -8% 0px' } = {}) {
  const els = [...document.querySelectorAll(selector)];
  if (dvReduce || !('IntersectionObserver' in window)) {
    els.forEach((el) => el.classList.add('is-in'));
    return;
  }
  const io = new IntersectionObserver((entries) => {
    for (const e of entries) {
      if (e.isIntersecting) {
        e.target.classList.add('is-in');
        if (e.target.dataset.reveal !== 'repeat') io.unobserve(e.target);
      } else if (e.target.dataset.reveal === 'repeat') {
        e.target.classList.remove('is-in');
      }
    }
  }, { threshold, rootMargin });
  els.forEach((el) => io.observe(el));
}

/**
 * スクロール量を 0〜1 にして、各 [data-progress] 要素の CSS 変数 --p に書く。
 *   data-progress="through" : 要素の上端が画面の下端に来たとき 0、下端が画面の上端を抜けたとき 1
 *   data-progress="pin"     : 要素の上端が画面の上端に来たとき 0、下端が画面の下端に来たとき 1
 *                             （中に position: sticky の箱を持つ、背の高い区画用）
 *   data-progress="page"    : ページ全体のスクロール量
 * onUpdate(el, p) を渡すと、値が変わるたびに呼ばれる。
 */
function dvProgress(onUpdate) {
  const els = [...document.querySelectorAll('[data-progress]')];
  const clamp = (n) => Math.min(1, Math.max(0, n));
  let queued = false;
  const measure = () => {
    queued = false;
    const vh = window.innerHeight;
    for (const el of els) {
      const r = el.getBoundingClientRect();
      let p;
      if (el.dataset.progress === 'pin') p = r.height > vh ? -r.top / (r.height - vh) : 0;
      else if (el.dataset.progress === 'page') {
        const max = document.documentElement.scrollHeight - vh;
        p = max > 0 ? window.scrollY / max : 0;
      } else p = (vh - r.top) / (vh + r.height);
      p = clamp(p);
      el.style.setProperty('--p', p.toFixed(4));
      if (onUpdate) onUpdate(el, p);
    }
  };
  const request = () => {
    if (!queued) { queued = true; requestAnimationFrame(measure); }
  };
  addEventListener('scroll', request, { passive: true });
  addEventListener('resize', request);
  measure();
}
/* dv-motion-helpers:end */

/* ---- この演出だけの JS ---- */
const curtainSecs = [...document.querySelectorAll('.curtain-sec')];
// 区画 1 は p の前半、区画 2 は後半で持ち上がる。区画 3 は最後まで残る。
dvProgress((el, p) => {
  curtainSecs.slice(0, -1).forEach((s, k) => {
    const q = Math.min(1, Math.max(0, p * 2 - k));
    s.style.setProperty('--q', q.toFixed(4));
  });
});
</script>
</body>
</html>

/ai/assets/motion-curtain-reveal.json