04Hero shrink parallax

<main class="stage is-demo">
  <div class="heroshrink">
    <h2 class="heroshrink__title">A hero that shrinks</h2>
  </div>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 ──────────────────────────
$scale-to: .55;                                  // 다 스크롤했을 때 남는 크기
$duration: $dur-loop;                            // 데모 왕복 주기
$color: $subject-blue;                           // 제목 색 (paper 무대라 blue)

@include stage($stage-paper);

.heroshrink {
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
}
.heroshrink__title {
  margin: 0;
  color: $color;
  font: 800 clamp(22px, 8vw, 34px)/1.1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  text-align: center;

  // ── 실제 사용 코드: 스크롤하는 동안 작아지고 옅어진다 ──
  @supports (animation-timeline: scroll()) {
    animation: shrink linear both;
    animation-timeline: scroll(root);
  }
  @supports not (animation-timeline: scroll()) { transform: none; opacity: 1; }
}

@keyframes shrink { from { transform: scale(1); opacity: 1; } to { transform: scale(#{$scale-to}); opacity: .25; } }

// ── 데모(.is-demo): 왕복 루프로 흉내 ────────
.stage.is-demo .heroshrink__title { animation: shrink-loop $duration ease-in-out infinite; }
@keyframes shrink-loop {
  0%, 100% { transform: scale(1); opacity: 1; }
  50%      { transform: scale($scale-to); opacity: .25; }
}

@media (prefers-reduced-motion: reduce) {
  .heroshrink__title, .stage.is-demo .heroshrink__title { animation: none !important; transform: none; opacity: 1; }
}

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

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

.heroshrink {
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
}

.heroshrink__title {
  margin: 0;
  color: #2f6df6;
  font: 800 clamp(22px, 8vw, 34px)/1.1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  text-align: center;
}
@supports (animation-timeline: scroll()) {
  .heroshrink__title {
    animation: shrink linear both;
    animation-timeline: scroll(root);
  }
}
@supports not (animation-timeline: scroll()) {
  .heroshrink__title {
    transform: none;
    opacity: 1;
  }
}

@keyframes shrink {
  from {
    transform: scale(1);
    opacity: 1;
  }
  to {
    transform: scale(0.55);
    opacity: 0.25;
  }
}
.stage.is-demo .heroshrink__title {
  animation: shrink-loop 2s ease-in-out infinite;
}

@keyframes shrink-loop {
  0%, 100% {
    transform: scale(1);
    opacity: 1;
  }
  50% {
    transform: scale(0.55);
    opacity: 0.25;
  }
}
@media (prefers-reduced-motion: reduce) {
  .heroshrink__title, .stage.is-demo .heroshrink__title {
    animation: none !important;
    transform: none;
    opacity: 1;
  }
}

import type { CSSProperties, ReactNode } from "react";
import styles from "./HeroShrink.module.scss";

export type HeroShrinkProps = {
  children: ReactNode;
  /** 다 스크롤했을 때 남는 크기 (기본 .55) */
  scaleTo?: number;
  /** 제목 색 */
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--scale-to"?: string; "--color"?: string };

export default function HeroShrink({
  children,
  scaleTo = 0.55,
  color = "#2f6df6",
  className = "",
}: HeroShrinkProps) {
  const vars: Vars = { "--scale-to": `${scaleTo}`, "--color": color };

  return (
    <div className={`${styles.wrap} ${className}`} style={vars}>
      <h2 className={styles.title}>{children}</h2>
    </div>
  );
}