05Scanline mask sweep

<main class="stage">
  <div class="sl-wrap is-demo">
    <span class="sl-text">SCANNED</span>
    <span class="sl-noise" aria-hidden="true"></span>
    <span class="sl-beam" aria-hidden="true"></span>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-cream;

@include stage($stage-ink);

.sl-wrap {
  position: relative;
  display: inline-block;
  overflow: hidden;
  padding: $sp-2 $sp-3;
}

.sl-text {
  display: block;
  font: 800 clamp(22px, 7vw, 34px)/1.2 "Space Mono", "Courier New", monospace;
  color: $color;
  letter-spacing: .04em;
}

.sl-noise {
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(45deg, rgba(255, 255, 255, .4) 0 2px, transparent 2px 4px);
  mix-blend-mode: screen;
}

.sl-beam {
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  height: 3px;
  background: $stage-yellow;
  box-shadow: 0 0 12px $stage-yellow;
  opacity: 0;
}

// 데모 루프: 노이즈 블록이 글자를 덮고 있다가 스캔라인이 위→아래로 지나가며 걷어낸다
@keyframes sl-clear {
  0%, 8% { clip-path: inset(0 0 0 0); }
  55%, 78% { clip-path: inset(100% 0 0 0); }
  100% { clip-path: inset(0 0 0 0); }
}
@keyframes sl-beam {
  0%, 8% { top: 0; opacity: 1; }
  55% { top: 100%; opacity: 1; }
  63%, 100% { opacity: 0; }
}

.sl-wrap.is-demo .sl-noise { animation: sl-clear $duration $easing infinite; }
.sl-wrap.is-demo .sl-beam { animation: sl-beam $duration $easing infinite; }

@media (prefers-reduced-motion: reduce) {
  .sl-noise, .sl-wrap.is-demo .sl-noise { animation: none !important; clip-path: inset(100% 0 0 0) !important; }
  .sl-beam, .sl-wrap.is-demo .sl-beam { animation: none !important; opacity: 0 !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);
}

.sl-wrap {
  position: relative;
  display: inline-block;
  overflow: hidden;
  padding: 8px 12px;
}

.sl-text {
  display: block;
  font: 800 clamp(22px, 7vw, 34px)/1.2 "Space Mono", "Courier New", monospace;
  color: #fff7e6;
  letter-spacing: 0.04em;
}

.sl-noise {
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(45deg, rgba(255, 255, 255, 0.4) 0 2px, transparent 2px 4px);
  mix-blend-mode: screen;
}

.sl-beam {
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  height: 3px;
  background: #ffd23f;
  box-shadow: 0 0 12px #ffd23f;
  opacity: 0;
}

@keyframes sl-clear {
  0%, 8% {
    clip-path: inset(0 0 0 0);
  }
  55%, 78% {
    clip-path: inset(100% 0 0 0);
  }
  100% {
    clip-path: inset(0 0 0 0);
  }
}
@keyframes sl-beam {
  0%, 8% {
    top: 0;
    opacity: 1;
  }
  55% {
    top: 100%;
    opacity: 1;
  }
  63%, 100% {
    opacity: 0;
  }
}
.sl-wrap.is-demo .sl-noise {
  animation: sl-clear 2s ease-out infinite;
}

.sl-wrap.is-demo .sl-beam {
  animation: sl-beam 2s ease-out infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sl-noise, .sl-wrap.is-demo .sl-noise {
    animation: none !important;
    clip-path: inset(100% 0 0 0) !important;
  }
  .sl-beam, .sl-wrap.is-demo .sl-beam {
    animation: none !important;
    opacity: 0 !important;
  }
}

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

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

// 실사용: 뷰포트에 들어오면 노이즈 블록을 스캔라인이 위→아래로 한 번 훑어 글자를 드러낸다.
export default function ScanlineMaskSweep({
  text = "SCANNED",
  duration = "900ms",
  easing = "ease-out",
}: ScanlineMaskSweepProps) {
  const ref = useRef<HTMLDivElement>(null);
  const [swept, setSwept] = useState(false);

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

  const style = { "--duration": duration, "--easing": easing } as CSSProperties;

  return (
    <div className={styles.wrap} style={style} ref={ref}>
      <span className={styles.text}>{text}</span>
      <span className={`${styles.noise} ${swept ? styles.clear : ""}`} aria-hidden="true" />
      <span className={`${styles.beam} ${swept ? styles.moved : ""}`} aria-hidden="true" />
    </div>
  );
}