09Radar sweep fill

<main class="stage">
  <div class="rs-wrap is-demo">
    <span class="rs-sweep" aria-hidden="true"></span>
    <p class="rs-text">
      <span>D</span><span>E</span><span>T</span><span>E</span><span>C</span><span>T</span><span>E</span><span>D</span>
    </p>
  </div>
</main>

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

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

@include stage($stage-ink);

.rs-wrap {
  position: relative;
  overflow: hidden;
  padding: $sp-6;
  border-radius: $r-card;
}

.rs-sweep {
  position: absolute;
  inset: -60%;
  background: conic-gradient(from 0deg, transparent 0deg, rgba(61, 220, 132, .5) 10deg, transparent 34deg);
  border-radius: $r-pill;
  mix-blend-mode: screen;
}

.rs-text {
  position: relative;
  margin: 0;
  display: flex;
  gap: 0;
  font: 800 clamp(18px, 6vw, 28px)/1.2 "Space Mono", "Courier New", monospace;
  color: $color;
}

.rs-text span { opacity: .16; }

@keyframes rs-rotate { to { transform: rotate(360deg); } }
@keyframes rs-lock {
  0%, 4% { opacity: .16; }
  14%, 88% { opacity: 1; }
  100% { opacity: .16; }
}

.rs-wrap.is-demo .rs-sweep { animation: rs-rotate $duration linear infinite; }

.rs-wrap.is-demo .rs-text span {
  animation: rs-lock $duration $easing infinite;
}
@for $i from 1 through 8 {
  .rs-wrap.is-demo .rs-text span:nth-child(#{$i}) { animation-delay: calc(#{$duration} / 8 * #{$i - 1}); }
}

@media (prefers-reduced-motion: reduce) {
  .rs-sweep,
  .rs-wrap.is-demo .rs-sweep { animation: none !important; opacity: 0 !important; }
  .rs-text span,
  .rs-wrap.is-demo .rs-text span { animation: none !important; opacity: 1 !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);
}

.rs-wrap {
  position: relative;
  overflow: hidden;
  padding: 24px;
  border-radius: 16px;
}

.rs-sweep {
  position: absolute;
  inset: -60%;
  background: conic-gradient(from 0deg, transparent 0deg, rgba(61, 220, 132, 0.5) 10deg, transparent 34deg);
  border-radius: 999px;
  mix-blend-mode: screen;
}

.rs-text {
  position: relative;
  margin: 0;
  display: flex;
  gap: 0;
  font: 800 clamp(18px, 6vw, 28px)/1.2 "Space Mono", "Courier New", monospace;
  color: #fff7e6;
}

.rs-text span {
  opacity: 0.16;
}

@keyframes rs-rotate {
  to {
    transform: rotate(360deg);
  }
}
@keyframes rs-lock {
  0%, 4% {
    opacity: 0.16;
  }
  14%, 88% {
    opacity: 1;
  }
  100% {
    opacity: 0.16;
  }
}
.rs-wrap.is-demo .rs-sweep {
  animation: rs-rotate 2s linear infinite;
}

.rs-wrap.is-demo .rs-text span {
  animation: rs-lock 2s ease-out infinite;
}

.rs-wrap.is-demo .rs-text span:nth-child(1) {
  animation-delay: calc(2s / 8 * 0);
}

.rs-wrap.is-demo .rs-text span:nth-child(2) {
  animation-delay: calc(2s / 8 * 1);
}

.rs-wrap.is-demo .rs-text span:nth-child(3) {
  animation-delay: calc(2s / 8 * 2);
}

.rs-wrap.is-demo .rs-text span:nth-child(4) {
  animation-delay: calc(2s / 8 * 3);
}

.rs-wrap.is-demo .rs-text span:nth-child(5) {
  animation-delay: calc(2s / 8 * 4);
}

.rs-wrap.is-demo .rs-text span:nth-child(6) {
  animation-delay: calc(2s / 8 * 5);
}

.rs-wrap.is-demo .rs-text span:nth-child(7) {
  animation-delay: calc(2s / 8 * 6);
}

.rs-wrap.is-demo .rs-text span:nth-child(8) {
  animation-delay: calc(2s / 8 * 7);
}

@media (prefers-reduced-motion: reduce) {
  .rs-sweep,
  .rs-wrap.is-demo .rs-sweep {
    animation: none !important;
    opacity: 0 !important;
  }
  .rs-text span,
  .rs-wrap.is-demo .rs-text span {
    animation: none !important;
    opacity: 1 !important;
  }
}

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

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

// 실사용: 뷰포트에 들어오면 레이더 스윕이 한 바퀴 돌며 지나간 자리의 글자만 순서대로 선명해진다.
export default function RadarSweepFill({
  text = "DETECTED",
  duration = "1400ms",
  easing = "ease-out",
}: RadarSweepFillProps) {
  const ref = useRef<HTMLDivElement>(null);
  const [locked, setLocked] = useState(0);
  const [sweeping, setSweeping] = useState(false);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    let timer: ReturnType<typeof setInterval> | null = null;
    const io = new IntersectionObserver((entries) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting || timer) return;
        io.unobserve(entry.target);
        const reduced = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
        if (reduced) { setLocked(text.length); return; }
        setSweeping(true);
        let i = 0;
        timer = setInterval(() => {
          i += 1;
          setLocked(i);
          if (i >= text.length && timer) { clearInterval(timer); timer = null; setSweeping(false); }
        }, 160);
      });
    }, { threshold: 0.3 });
    io.observe(el);
    return () => { io.disconnect(); if (timer) clearInterval(timer); };
  }, [text]);

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

  return (
    <div className={styles.wrap} style={style} ref={ref}>
      <span className={`${styles.sweep} ${sweeping ? styles.spin : ""}`} aria-hidden="true" />
      <p className={styles.text}>
        {text.split("").map((ch, i) => (
          <span key={i} style={{ opacity: i < locked ? 1 : 0.16 }}>{ch}</span>
        ))}
      </p>
    </div>
  );
}