04Masonry stagger fade

<main class="stage">
  <div class="mf-grid is-demo">
    <div class="mf-tile mf-tile--a"></div>
    <div class="mf-tile mf-tile--b"></div>
    <div class="mf-tile mf-tile--c"></div>
    <div class="mf-tile mf-tile--d"></div>
    <div class="mf-tile mf-tile--e"></div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-out;
$stagger: 140ms;

@include stage($stage-paper);

.mf-grid {
  width: min(260px, 78vw);
  columns: 2;
  column-gap: $sp-2;
}

.mf-tile {
  break-inside: avoid;
  margin-bottom: $sp-2;
  border-radius: $r-sm;
  box-shadow: $shadow-press;
  // 진짜 등장 전 상태 — transition 경로와 keyframes 경로가 같은 시작점을 공유한다
  opacity: 0;
  transform: translateY($sp-4);
}

.mf-tile--a { height: 52px; background: radial-gradient(26px circle at 30% 30%, rgba(255,255,255,.6), transparent 60%), linear-gradient(150deg, $subject-blue, $subject-ink); }
.mf-tile--b { height: 36px; background: radial-gradient(22px circle at 70% 60%, rgba(255,255,255,.6), transparent 60%), linear-gradient(150deg, $subject-cream, $subject-blue); }
.mf-tile--c { height: 44px; background: radial-gradient(24px circle at 40% 70%, rgba(255,255,255,.6), transparent 60%), linear-gradient(150deg, $subject-ink, $subject-cream); }
.mf-tile--d { height: 56px; background: radial-gradient(26px circle at 60% 30%, rgba(255,255,255,.6), transparent 60%), linear-gradient(150deg, $subject-blue, $subject-cream); }
.mf-tile--e { height: 32px; background: radial-gradient(18px circle at 50% 50%, rgba(255,255,255,.6), transparent 60%), linear-gradient(150deg, $subject-cream, $subject-ink); }

// 실사용: 진짜 IntersectionObserver 가 뷰포트에 들어올 때 .in 을 붙인다(위 <script>). 타일마다 delay 만 다르다
.mf-tile { transition: opacity 400ms $easing, transform 400ms $easing; }
.mf-tile.in { opacity: 1; transform: translateY(0); }
.mf-tile--a.in { transition-delay: 0; }
.mf-tile--b.in { transition-delay: $stagger; }
.mf-tile--c.in { transition-delay: $stagger * 2; }
.mf-tile--d.in { transition-delay: $stagger * 3; }
.mf-tile--e.in { transition-delay: $stagger * 4; }

// 데모 루프: is-demo 는 transition 경로를 쓰지 않는다 — 같은 순차 등장을 keyframes 로 무한 재생(캡처용)
@keyframes mf-tile-in {
  0%   { opacity: 0; transform: translateY($sp-4); }
  20%  { opacity: 1; transform: translateY(0); }
  100% { opacity: 1; transform: translateY(0); }
}
.mf-grid.is-demo .mf-tile { animation: mf-tile-in $duration $easing infinite; animation-fill-mode: both; }
.mf-grid.is-demo .mf-tile--a { animation-delay: 0ms; }
.mf-grid.is-demo .mf-tile--b { animation-delay: $stagger; }
.mf-grid.is-demo .mf-tile--c { animation-delay: $stagger * 2; }
.mf-grid.is-demo .mf-tile--d { animation-delay: $stagger * 3; }
.mf-grid.is-demo .mf-tile--e { animation-delay: $stagger * 4; }

@media (prefers-reduced-motion: reduce) {
  .mf-tile, .mf-tile.in, .mf-grid.is-demo .mf-tile {
    animation: none !important; transition: none !important; opacity: 1 !important; transform: none !important;
  }
}

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);
}

.mf-grid {
  width: min(260px, 78vw);
  columns: 2;
  column-gap: 8px;
}

.mf-tile {
  break-inside: avoid;
  margin-bottom: 8px;
  border-radius: 8px;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  opacity: 0;
  transform: translateY(16px);
}

.mf-tile--a {
  height: 52px;
  background: radial-gradient(26px circle at 30% 30%, rgba(255, 255, 255, 0.6), transparent 60%), linear-gradient(150deg, #2f6df6, #17141a);
}

.mf-tile--b {
  height: 36px;
  background: radial-gradient(22px circle at 70% 60%, rgba(255, 255, 255, 0.6), transparent 60%), linear-gradient(150deg, #fff7e6, #2f6df6);
}

.mf-tile--c {
  height: 44px;
  background: radial-gradient(24px circle at 40% 70%, rgba(255, 255, 255, 0.6), transparent 60%), linear-gradient(150deg, #17141a, #fff7e6);
}

.mf-tile--d {
  height: 56px;
  background: radial-gradient(26px circle at 60% 30%, rgba(255, 255, 255, 0.6), transparent 60%), linear-gradient(150deg, #2f6df6, #fff7e6);
}

.mf-tile--e {
  height: 32px;
  background: radial-gradient(18px circle at 50% 50%, rgba(255, 255, 255, 0.6), transparent 60%), linear-gradient(150deg, #fff7e6, #17141a);
}

.mf-tile {
  transition: opacity 400ms ease-out, transform 400ms ease-out;
}

.mf-tile.in {
  opacity: 1;
  transform: translateY(0);
}

.mf-tile--a.in {
  transition-delay: 0;
}

.mf-tile--b.in {
  transition-delay: 140ms;
}

.mf-tile--c.in {
  transition-delay: 280ms;
}

.mf-tile--d.in {
  transition-delay: 420ms;
}

.mf-tile--e.in {
  transition-delay: 560ms;
}

@keyframes mf-tile-in {
  0% {
    opacity: 0;
    transform: translateY(16px);
  }
  20% {
    opacity: 1;
    transform: translateY(0);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}
.mf-grid.is-demo .mf-tile {
  animation: mf-tile-in 2s ease-out infinite;
  animation-fill-mode: both;
}

.mf-grid.is-demo .mf-tile--a {
  animation-delay: 0ms;
}

.mf-grid.is-demo .mf-tile--b {
  animation-delay: 140ms;
}

.mf-grid.is-demo .mf-tile--c {
  animation-delay: 280ms;
}

.mf-grid.is-demo .mf-tile--d {
  animation-delay: 420ms;
}

.mf-grid.is-demo .mf-tile--e {
  animation-delay: 560ms;
}

@media (prefers-reduced-motion: reduce) {
  .mf-tile, .mf-tile.in, .mf-grid.is-demo .mf-tile {
    animation: none !important;
    transition: none !important;
    opacity: 1 !important;
    transform: none !important;
  }
}

var tiles = document.querySelectorAll('.mf-tile');
var io = new IntersectionObserver(function (entries) {
  entries.forEach(function (e) { if (e.isIntersecting) { e.target.classList.add('in'); io.unobserve(e.target); } });
}, { threshold: 0.3 });
tiles.forEach(function (t) { io.observe(t); });

import { CSSProperties, useEffect, useRef, useState } from "react";
import styles from "./MasonryFadeStagger.module.scss";

export interface MasonryFadeStaggerProps {
  duration?: string;
  easing?: string;
  stagger?: number;
}

const TILES = ["a", "b", "c", "d", "e"] as const;

export default function MasonryFadeStagger({
  duration = "400ms",
  easing = "ease-out",
  stagger = 140,
}: MasonryFadeStaggerProps) {
  const ref = useRef<HTMLDivElement>(null);
  const [inView, setInView] = useState(false);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const io = new IntersectionObserver(
      (entries) => entries.forEach((e) => e.isIntersecting && setInView(true)),
      { threshold: 0.3 }
    );
    io.observe(el);
    return () => io.disconnect();
  }, []);

  return (
    <div ref={ref} className={styles.grid}>
      {TILES.map((t, i) => {
        const style: CSSProperties = {
          transitionDuration: duration,
          transitionTimingFunction: easing,
          transitionDelay: inView ? `${i * stagger}ms` : "0ms",
        };
        return (
          <div
            key={t}
            className={`${styles.tile} ${styles["tile" + t.toUpperCase()]} ${inView ? styles.in : ""}`}
            style={style}
          />
        );
      })}
    </div>
  );
}