01Hero — an intro where background and heading shift at different scroll ratios

<main class="stage" id="stage">
  <div class="hero__bg" aria-hidden="true"></div>
  <div class="hero__head">
    <p class="hero__eyebrow">New</p>
    <h1 class="hero__title">A lightweight landing page</h1>
    <p class="hero__sub">One scroll value moves two layers at different ratios.</p>
    <button class="hero__cta" type="button">Get started</button>
  </div>
</main>

@use "../../../../site/static/demo-tokens" as *;

$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-cream;

@include stage($stage-ink);

@property --sv {
  syntax: "<number>";
  inherits: true;
  initial-value: 0;
}

.stage {
  --sv: 0;
  position: relative;
  overflow: hidden;
  animation: scroll-sim $duration $easing infinite;
}

.hero__bg {
  position: absolute;
  inset: -10% -10% -30% -10%;
  border-radius: $r-card;
  background: linear-gradient(180deg, rgba($color, .28), rgba($color, 0));
  transform: translateY(calc(var(--sv) * -18px));
}

.hero__head {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: $sp-2;
  padding: $sp-8 $sp-6;
  transform: translateY(calc(var(--sv) * -42px));
}

.hero__eyebrow {
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba($color, .16);
  color: $color;
  font-weight: 600;
  font-size: 11px;
  line-height: 1.6;
}

.hero__title {
  margin: 0;
  color: $stage-paper;
  font-weight: 700;
  font-size: clamp(20px, 6vmin, 28px);
  line-height: 1.25;
}

.hero__sub {
  margin: 0;
  max-width: 34ch;
  color: rgba($stage-paper, .78);
  font-weight: 400;
  font-size: 13px;
  line-height: 1.55;
}

.hero__cta {
  margin-top: $sp-2;
  border: 0;
  border-radius: $r-pill;
  padding: $sp-3 $sp-6;
  font-family: inherit;
  font-weight: 600;
  font-size: 13px;
  line-height: 1;
  color: $stage-ink;
  background: $color;
  cursor: pointer;
}

@keyframes scroll-sim {
  0%, 8% { --sv: 0; }
  50% { --sv: 1; }
  92%, 100% { --sv: 0; }
}

@media (max-width: 340px) {
  .hero__head { padding: $sp-3 $sp-4; gap: $sp-1; }
  .hero__sub { max-width: 26ch; }
  .hero__cta { margin-top: 0; padding: $sp-2 $sp-4; }
}

@media (prefers-reduced-motion: reduce) {
  .stage { animation: none; }
  .hero__bg, .hero__head { transform: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

@property --sv {
  syntax: "<number>";
  inherits: true;
  initial-value: 0;
}
.stage {
  --sv: 0;
  position: relative;
  overflow: hidden;
  animation: scroll-sim 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.hero__bg {
  position: absolute;
  inset: -10% -10% -30% -10%;
  border-radius: 16px;
  background: linear-gradient(180deg, rgba(255, 247, 230, 0.28), rgba(255, 247, 230, 0));
  transform: translateY(calc(var(--sv) * -18px));
}

.hero__head {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 8px;
  padding: 32px 24px;
  transform: translateY(calc(var(--sv) * -42px));
}

.hero__eyebrow {
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.16);
  color: #fff7e6;
  font-weight: 600;
  font-size: 11px;
  line-height: 1.6;
}

.hero__title {
  margin: 0;
  color: #ffffff;
  font-weight: 700;
  font-size: clamp(20px, 6vmin, 28px);
  line-height: 1.25;
}

.hero__sub {
  margin: 0;
  max-width: 34ch;
  color: rgba(255, 255, 255, 0.78);
  font-weight: 400;
  font-size: 13px;
  line-height: 1.55;
}

.hero__cta {
  margin-top: 8px;
  border: 0;
  border-radius: 999px;
  padding: 12px 24px;
  font-family: inherit;
  font-weight: 600;
  font-size: 13px;
  line-height: 1;
  color: #17141a;
  background: #fff7e6;
  cursor: pointer;
}

@keyframes scroll-sim {
  0%, 8% {
    --sv: 0;
  }
  50% {
    --sv: 1;
  }
  92%, 100% {
    --sv: 0;
  }
}
@media (max-width: 340px) {
  .hero__head {
    padding: 12px 16px;
    gap: 4px;
  }
  .hero__sub {
    max-width: 26ch;
  }
  .hero__cta {
    margin-top: 0;
    padding: 8px 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage {
    animation: none;
  }
  .hero__bg, .hero__head {
    transform: none;
  }
}

import styles from "./Hero.module.scss";

// 스크롤 값 하나(--sv)를 두 층(배경·헤드)이 서로 다른 비율(-18px, -42px)로 받아 시차 효과를 만든다.
// 계산 겹: 스크롤 값(--sv) -> 두 층 각각의 translateY 비율 보간. 리스너 없음(자동 재생).
export default function Hero() {
  return (
    <main className={styles.stage}>
      <div className={styles.hero__bg} aria-hidden="true" />
      <div className={styles.hero__head}>
        <p className={styles.hero__eyebrow}>신제품</p>
        <h1 className={styles.hero__title}>가벼운 랜딩 페이지</h1>
        <p className={styles.hero__sub}>스크롤 값 하나로 두 층이 서로 다른 비율로 움직입니다.</p>
        <button className={styles.hero__cta} type="button">
          지금 시작하기
        </button>
      </div>
    </main>
  );
}