07Parallax layers

<main class="stage is-demo">
  <div class="parallax">
    <div class="parallax__back" aria-hidden="true"></div>
    <div class="parallax__front">
      <h2 class="parallax__title">Depth takes shape</h2>
    </div>
  </div>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 (값은 토큰에서 받는다) ──────
$back-shift: 20px;                               // 뒤 배경 이동량 (0.3배 느낌)
$front-shift: 40px;                              // 앞 내용 이동량 (0.5배 느낌)
$color: $subject-cream;                          // 뒤 배경 원 색 (orange 무대라 cream)

// ── 데모 무대 (zip 에서 지워도 된다) ──────────────────────────
html, body { margin: 0; overflow: hidden; }
.stage {
  position: relative;
  min-height: 100vh;
  margin: 0;
  overflow: hidden;
  background: $stage-orange;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.parallax {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;

  &__back {
    position: absolute;
    inset: -20% -20%;
    background:
      radial-gradient($color 0 60px, transparent 61px) 20% 30%,
      radial-gradient($color 0 40px, transparent 41px) 75% 65%;
    background-repeat: no-repeat;
    opacity: .55;

    // ── 실제 사용 코드: 뒤 배경은 스크롤보다 느리게(0.3배) 움직인다 ──
    @supports (animation-timeline: scroll()) {
      animation: drift-back linear both;
      animation-timeline: scroll(root);
    }
    @supports not (animation-timeline: scroll()) {
      transform: none;
    }
  }

  &__front {
    position: relative;
    z-index: 1;

    // ── 실제 사용 코드: 앞 내용은 뒤보다 빠르게(0.5배) 움직인다 ──
    @supports (animation-timeline: scroll()) {
      animation: drift-front linear both;
      animation-timeline: scroll(root);
    }
    @supports not (animation-timeline: scroll()) {
      transform: none;
    }
  }

  &__title {
    margin: 0;
    padding: 14px 22px;
    border-radius: $r-pill;
    background: $stage-ink;
    color: #fff;
    font-weight: 700;
    font-size: clamp(16px, 5vw, 20px);
    line-height: 1;
    font-family: inherit;
  }
}

@keyframes drift-back  { from { transform: translateY(0); } to { transform: translateY(-#{$back-shift}); } }
@keyframes drift-front { from { transform: translateY(0); } to { transform: translateY(-#{$front-shift}); } }

// ── 데모(.is-demo): 스크롤 대신 2초 왕복 루프로 흉내 ────────
.stage.is-demo .parallax__back {
  animation: drift-back-loop $dur-loop ease-in-out infinite;
}
.stage.is-demo .parallax__front {
  animation: drift-front-loop $dur-loop ease-in-out infinite;
}
@keyframes drift-back-loop {
  0%, 100% { transform: translateY($back-shift); }
  50%      { transform: translateY(-$back-shift); }
}
@keyframes drift-front-loop {
  0%, 100% { transform: translateY($front-shift); }
  50%      { transform: translateY(-$front-shift); }
}

// ── 접근성: 움직임 줄이기 설정이면 층을 그대로 고정 ────────────
@media (prefers-reduced-motion: reduce) {
  .parallax__back, .parallax__front,
  .stage.is-demo .parallax__back, .stage.is-demo .parallax__front {
    animation: none !important;
    transform: none;
  }
}

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

.stage {
  position: relative;
  min-height: 100vh;
  margin: 0;
  overflow: hidden;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.parallax {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
}
.parallax__back {
  position: absolute;
  inset: -20% -20%;
  background: radial-gradient(#fff7e6 0 60px, transparent 61px) 20% 30%, radial-gradient(#fff7e6 0 40px, transparent 41px) 75% 65%;
  background-repeat: no-repeat;
  opacity: 0.55;
}
@supports (animation-timeline: scroll()) {
  .parallax__back {
    animation: drift-back linear both;
    animation-timeline: scroll(root);
  }
}
@supports not (animation-timeline: scroll()) {
  .parallax__back {
    transform: none;
  }
}
.parallax__front {
  position: relative;
  z-index: 1;
}
@supports (animation-timeline: scroll()) {
  .parallax__front {
    animation: drift-front linear both;
    animation-timeline: scroll(root);
  }
}
@supports not (animation-timeline: scroll()) {
  .parallax__front {
    transform: none;
  }
}
.parallax__title {
  margin: 0;
  padding: 14px 22px;
  border-radius: 999px;
  background: #17141a;
  color: #fff;
  font-weight: 700;
  font-size: clamp(16px, 5vw, 20px);
  line-height: 1;
  font-family: inherit;
}

@keyframes drift-back {
  from {
    transform: translateY(0);
  }
  to {
    transform: translateY(-20px);
  }
}
@keyframes drift-front {
  from {
    transform: translateY(0);
  }
  to {
    transform: translateY(-40px);
  }
}
.stage.is-demo .parallax__back {
  animation: drift-back-loop 2s ease-in-out infinite;
}

.stage.is-demo .parallax__front {
  animation: drift-front-loop 2s ease-in-out infinite;
}

@keyframes drift-back-loop {
  0%, 100% {
    transform: translateY(20px);
  }
  50% {
    transform: translateY(-20px);
  }
}
@keyframes drift-front-loop {
  0%, 100% {
    transform: translateY(40px);
  }
  50% {
    transform: translateY(-40px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .parallax__back, .parallax__front,
  .stage.is-demo .parallax__back, .stage.is-demo .parallax__front {
    animation: none !important;
    transform: none;
  }
}

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

export type ParallaxLayersProps = {
  children: ReactNode;
  /** 뒤 배경 이동량 (기본 20px, 0.3배 느낌) */
  backShift?: number;
  /** 앞 내용 이동량 (기본 40px, 0.5배 느낌) */
  frontShift?: number;
  /** 뒤 배경 원 색 */
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--back-shift"?: string; "--front-shift"?: string; "--color"?: string };

export default function ParallaxLayers({
  children,
  backShift = 20,
  frontShift = 40,
  color = "#fff7e6",
  className = "",
}: ParallaxLayersProps) {
  const vars: Vars = {
    "--back-shift": `${backShift}px`,
    "--front-shift": `${frontShift}px`,
    "--color": color,
  };

  return (
    <div className={`${styles.parallax} ${className}`} style={vars}>
      <div className={styles.back} aria-hidden="true" />
      <div className={styles.front}>{children}</div>
    </div>
  );
}