08Tiles reveal via scroll stagger

<main class="stage">
  <div class="ss-grid is-demo">
    <div class="ss-tile"><span class="ss-tile__tag">Design</span></div>
    <div class="ss-tile"><span class="ss-tile__tag">Build</span></div>
    <div class="ss-tile"><span class="ss-tile__tag">Ship</span></div>
    <div class="ss-tile"><span class="ss-tile__tag">Scale</span></div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-out;
$stagger: 160ms;

@include stage($stage-paper);

.ss-grid {
  width: min(320px, 88vw);
  aspect-ratio: 340 / 190;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  grid-template-rows: repeat(2, 1fr);
  gap: $sp-2;
}

.ss-tile {
  border-radius: $r-sm;
  padding: $sp-3;
  box-sizing: border-box;
  color: $subject-ink;
  background: rgba(23, 20, 26, .06);
  font: 600 12px/1 -apple-system, "Segoe UI", sans-serif;
  display: flex;
  align-items: flex-end;
  // 진짜 등장 전 상태 — transition 경로와 keyframes 경로가 같은 시작점을 공유한다
  opacity: 0;
  transform: translateY($sp-4);
}
.ss-tile__tag { opacity: .8; }

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

// 데모 루프: is-demo 는 transition 경로를 쓰지 않는다 — scroll-timeline·view() 대신 keyframes 로 같은 순차 등장을 무한 재생한다(캡처용)
@keyframes ss-tile-in {
  0%   { opacity: 0; transform: translateY($sp-4); }
  30%  { opacity: 1; transform: translateY(0); }
  100% { opacity: 1; transform: translateY(0); }
}
.ss-grid.is-demo .ss-tile {
  animation: ss-tile-in $duration $easing infinite;
  animation-fill-mode: both;
}
.ss-grid.is-demo .ss-tile:nth-child(1) { animation-delay: 0ms; }
.ss-grid.is-demo .ss-tile:nth-child(2) { animation-delay: $stagger; }
.ss-grid.is-demo .ss-tile:nth-child(3) { animation-delay: $stagger * 2; }
.ss-grid.is-demo .ss-tile:nth-child(4) { animation-delay: $stagger * 3; }

@media (prefers-reduced-motion: reduce) {
  .ss-tile, .ss-tile.in,
  .ss-grid.is-demo .ss-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);
}

.ss-grid {
  width: min(320px, 88vw);
  aspect-ratio: 340/190;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  grid-template-rows: repeat(2, 1fr);
  gap: 8px;
}

.ss-tile {
  border-radius: 8px;
  padding: 12px;
  box-sizing: border-box;
  color: #17141a;
  background: rgba(23, 20, 26, 0.06);
  font: 600 12px/1 -apple-system, "Segoe UI", sans-serif;
  display: flex;
  align-items: flex-end;
  opacity: 0;
  transform: translateY(16px);
}

.ss-tile__tag {
  opacity: 0.8;
}

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

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

.ss-tile:nth-child(1).in {
  transition-delay: 0ms;
}

.ss-tile:nth-child(2).in {
  transition-delay: 160ms;
}

.ss-tile:nth-child(3).in {
  transition-delay: 320ms;
}

.ss-tile:nth-child(4).in {
  transition-delay: 480ms;
}

@keyframes ss-tile-in {
  0% {
    opacity: 0;
    transform: translateY(16px);
  }
  30% {
    opacity: 1;
    transform: translateY(0);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}
.ss-grid.is-demo .ss-tile {
  animation: ss-tile-in 2s ease-out infinite;
  animation-fill-mode: both;
}

.ss-grid.is-demo .ss-tile:nth-child(1) {
  animation-delay: 0ms;
}

.ss-grid.is-demo .ss-tile:nth-child(2) {
  animation-delay: 160ms;
}

.ss-grid.is-demo .ss-tile:nth-child(3) {
  animation-delay: 320ms;
}

.ss-grid.is-demo .ss-tile:nth-child(4) {
  animation-delay: 480ms;
}

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

var tiles = document.querySelectorAll('.ss-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 "./ScrollStaggerTiles.module.scss";

type Vars = CSSProperties & {
  "--duration"?: string;
  "--easing"?: string;
  "--stagger"?: string;
};

export interface ScrollStaggerTilesProps {
  duration?: string;
  easing?: string;
  stagger?: string;
}

const LABELS = ["Design", "Build", "Ship", "Scale"];

// 실사용: 진짜 IntersectionObserver 가 그리드 전체가 뷰포트에 들어올 때 in 을 켠다. 타일마다 transition-delay 만 다르다.
// scroll-timeline / view() 는 쓰지 않는다 — 브라우저마다 렌더가 갈린다
export default function ScrollStaggerTiles({
  duration = "2s",
  easing = "ease-out",
  stagger = "160ms",
}: ScrollStaggerTilesProps) {
  const gridRef = useRef<HTMLDivElement>(null);
  const [inView, setInView] = useState(false);

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

  const style: Vars = {
    "--duration": duration,
    "--easing": easing,
    "--stagger": stagger,
  };

  return (
    <div className={styles.grid} style={style} ref={gridRef}>
      {LABELS.map((label, i) => (
        <div
          key={label}
          className={`${styles.tile} ${inView ? styles.in : ""}`}
          style={{ transitionDelay: inView ? `calc(${stagger} * ${i})` : undefined }}
        >
          <span className={styles.tag}>{label}</span>
        </div>
      ))}
    </div>
  );
}