09Shadow build

<main class="stage">
  <h2 class="sh-text is-demo">ARCADE</h2>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-lerp-settle; // 관성 lerp — 쌓이는 층이 목표 두께를 살짝 지나쳤다 정착한다 (2026-09-15 형태 2차 한 겹)
$color: $subject-cream;

@include stage($stage-ink);

.sh-text {
  margin: 0;
  font: 900 clamp(26px, 8vw, 40px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: $color;
  text-shadow: none;
  filter: blur(5px);
}

// 데모 루프: 평평한 글자 뒤로 그림자 층이 겹겹이 쌓이며 입체적인 두께가 생겼다가 다시 평평해진다
// 한 겹: 관성 lerp — $ease-lerp-settle 로 층 두께가 목표를 살짝 지나쳤다 되돌아오며 쌓이고(블록이 얹히듯),
// 같은 구간에서 blur(5px)→0 초점 수렴이 겹쳐 두꺼워질수록 또렷해진다.
@keyframes sh-extrude {
  0%, 15% { text-shadow: none; filter: blur(5px); }
  55%, 85% {
    text-shadow:
      1px 1px 0 $subject-blue,
      2px 2px 0 $subject-blue,
      3px 3px 0 $subject-blue,
      4px 4px 0 $subject-blue,
      5px 5px 8px rgba(0, 0, 0, .35);
    filter: blur(0);
  }
  100% { text-shadow: none; filter: blur(5px); }
}

.sh-text.is-demo { animation: sh-extrude $duration $easing infinite; }

@media (prefers-reduced-motion: reduce) {
  .sh-text,
  .sh-text.is-demo {
    animation: none !important;
    filter: none !important;
    text-shadow:
      1px 1px 0 $subject-blue,
      2px 2px 0 $subject-blue,
      3px 3px 0 $subject-blue,
      4px 4px 0 $subject-blue,
      5px 5px 8px rgba(0, 0, 0, .35) !important;
  }
}

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);
}

.sh-text {
  margin: 0;
  font: 900 clamp(26px, 8vw, 40px)/1.2 -apple-system, "Segoe UI", sans-serif;
  color: #fff7e6;
  text-shadow: none;
  filter: blur(5px);
}

@keyframes sh-extrude {
  0%, 15% {
    text-shadow: none;
    filter: blur(5px);
  }
  55%, 85% {
    text-shadow: 1px 1px 0 #2f6df6, 2px 2px 0 #2f6df6, 3px 3px 0 #2f6df6, 4px 4px 0 #2f6df6, 5px 5px 8px rgba(0, 0, 0, 0.35);
    filter: blur(0);
  }
  100% {
    text-shadow: none;
    filter: blur(5px);
  }
}
.sh-text.is-demo {
  animation: sh-extrude 2s linear(0, 0.051, 0.176, 0.341, 0.518, 0.685, 0.831, 0.947, 1.032, 1.087, 1.117, 1.126, 1.121, 1.105, 1.085, 1.062, 1.041, 1.022, 1.008, 0.997, 1) infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sh-text,
  .sh-text.is-demo {
    animation: none !important;
    filter: none !important;
    text-shadow: 1px 1px 0 #2f6df6, 2px 2px 0 #2f6df6, 3px 3px 0 #2f6df6, 4px 4px 0 #2f6df6, 5px 5px 8px rgba(0, 0, 0, 0.35) !important;
  }
}

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

export interface ShadowBuildProps {
  text?: string;
  duration?: string;
  easing?: string;
}

// 실사용: 뷰포트에 들어오면 평평한 글자 뒤로 그림자 층이 한 번 쌓이며 입체적인 두께가 생긴다.
export default function ShadowBuild({
  text = "ARCADE",
  duration = "500ms",
  easing = "ease-out",
}: ShadowBuildProps) {
  const ref = useRef<HTMLHeadingElement>(null);
  const [inView, setInView] = useState(false);

  useEffect(() => {
    const el = ref.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 = { "--duration": duration, "--easing": easing } as CSSProperties;

  return (
    <h2 className={`${styles.text} ${inView ? styles.in : ""}`} style={style} ref={ref}>
      {text}
    </h2>
  );
}