02Idle pulse — while waiting for authentication, a circular pulse's radius value grows under a decay function and fades as it grows

<main class="stage">
<div class="pulse-wrap">
<button type="button" class="pulse is-demo" id="pulse" aria-pressed="true">
  <svg class="pulse__icon" viewBox="0 0 120 120" aria-hidden="true">
    <circle class="pulse__ring" data-slot="0" cx="60" cy="60" r="0"></circle>
    <circle class="pulse__ring" data-slot="1" cx="60" cy="60" r="0"></circle>
    <circle class="pulse__ring" data-slot="2" cx="60" cy="60" r="0"></circle>
    <circle class="pulse__ring" data-slot="3" cx="60" cy="60" r="0"></circle>
    <circle class="pulse__core" cx="60" cy="60" r="14"></circle>
    <path class="pulse__mark" d="M52,64 A8 8 0 0 1 68,64" />
  </svg>
  <span class="pulse__label">Waiting for auth</span>
</button>
<p class="pulse__status" id="status">Listening</p>
</div>
</main>

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

// 계산 겹은 index.html 의 tick() 에 있다 — 펄스마다 뜬 뒤 지난 시간(age)에 지수 감쇠식을 걸어
// 반지름·불투명도를 매 프레임 다시 계산한다. 여기는 무대·모양만 맡는다.
@include stage($stage-paper);

.pulse-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.pulse {
  appearance: none;
  border: none;
  background: transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
  cursor: pointer;
  padding: $sp-4;
  border-radius: $r-card;

  &:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 4px; }
}

.pulse__icon {
  width: clamp(120px, 30vw, 160px);
  height: auto;
  overflow: visible;
}

.pulse__ring {
  fill: none;
  stroke: $subject-blue-light;
  stroke-width: 2;
  opacity: 0;
}

.pulse__core {
  fill: $subject-blue-deep;
}

.pulse__mark {
  fill: none;
  stroke: $subject-cream;
  stroke-width: 2;
  stroke-linecap: round;
}

.pulse__label {
  color: $stage-ink;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: .02em;
}

.pulse__status {
  margin: 0;
  color: rgba($stage-ink, .58);
  font-weight: 500;
  font-size: 12px;
  line-height: 1.2;
}

@media (max-width: 340px) {
  .stage { padding: $sp-2; }
  .pulse-wrap { gap: $sp-2; }
  .pulse { padding: $sp-2 $sp-3; gap: $sp-2; }
  .pulse__icon { width: 104px; }
  .pulse__label { font-size: 12px; }
  .pulse__status { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .pulse__ring { transition: none; }
}

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);
}

.pulse-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.pulse {
  appearance: none;
  border: none;
  background: transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  padding: 16px;
  border-radius: 16px;
}
.pulse:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 4px;
}

.pulse__icon {
  width: clamp(120px, 30vw, 160px);
  height: auto;
  overflow: visible;
}

.pulse__ring {
  fill: none;
  stroke: #5b8cf8;
  stroke-width: 2;
  opacity: 0;
}

.pulse__core {
  fill: #0a4fe8;
}

.pulse__mark {
  fill: none;
  stroke: #fff7e6;
  stroke-width: 2;
  stroke-linecap: round;
}

.pulse__label {
  color: #17141a;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: 0.02em;
}

.pulse__status {
  margin: 0;
  color: rgba(23, 20, 26, 0.58);
  font-weight: 500;
  font-size: 12px;
  line-height: 1.2;
}

@media (max-width: 340px) {
  .stage {
    padding: 8px;
  }
  .pulse-wrap {
    gap: 8px;
  }
  .pulse {
    padding: 8px 12px;
    gap: 8px;
  }
  .pulse__icon {
    width: 104px;
  }
  .pulse__label {
    font-size: 12px;
  }
  .pulse__status {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pulse__ring {
    transition: none;
  }
}

(function () {
  // 계산 겹: 감쇠 함수 — 새 펄스가 뜬 뒤 지난 시간(age)에 지수 감쇠식을 걸어
  // 반지름은 PULSE_MAX_R 로 점근하고(1 - e^(-age/TAU)), 밝기는 그 반지름 비율만큼 옅어진다.
  // 트윈(펄스 개수·타이밍)이 아니라 매 프레임 이 식을 다시 계산해서 그린다.
  var PULSE_MAX_R = 40; // 변형 02: PULSE_MAX_R 40 → 70 (펄스 최대 반경)
  var TAU = 260; // 감쇠 시간 상수(ms) — 클수록 천천히 옅어진다
  var LAUNCH_GAP = 550; // 새 펄스를 띄우는 간격(ms)
  var CUTOFF = TAU * 4.4; // 이 age 를 넘으면 슬롯을 반납한다(반지름이 사실상 MAX_R 에 도달)
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('pulse');
  var status = document.getElementById('status');
  var rings = Array.prototype.slice.call(document.querySelectorAll('.pulse__ring'));
  var STRINGS = { listening: 'Listening', paused: 'Paused' };
  var isDemo = true;
  var listening = true;
  var slots = rings.map(function (el) { return { el: el, start: null }; });
  var slotCursor = 0;
  var lastLaunch = 0;

  function spawn(now) {
    var slot = slots[slotCursor % slots.length];
    slotCursor++;
    slot.start = now;
  }

  function tick(now) {
    for (var i = 0; i < slots.length; i++) {
      var slot = slots[i];
      if (slot.start === null) { continue; }
      var age = now - slot.start;
      if (age > CUTOFF) {
        slot.start = null;
        slot.el.style.opacity = '0';
        continue;
      }
      var radius = PULSE_MAX_R * (1 - Math.exp(-age / TAU));
      var opacity = Math.max(0, 1 - radius / PULSE_MAX_R);
      slot.el.setAttribute('r', radius.toFixed(2));
      slot.el.style.opacity = opacity.toFixed(3);
    }
  }

  function human() { if (isDemo) { root.classList.remove('is-demo'); isDemo = false; } }

  function toggle() {
    listening = !listening;
    root.setAttribute('aria-pressed', String(listening));
    status.textContent = listening ? STRINGS.listening : STRINGS.paused;
  }

  root.addEventListener('click', function () { human(); toggle(); });
  root.addEventListener('keydown', function (e) {
    if (e.key === ' ' || e.key === 'Enter') { human(); }
  });

  function loop(ts) {
    var active = listening && (isDemo ? !reduce : true);
    if (active && ts - lastLaunch >= LAUNCH_GAP) {
      lastLaunch = ts;
      spawn(ts);
    }
    tick(ts);
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// RadialPulse — vanilla 판(run/371/demo/02-biometric-scan-radial-pulse/index.html) 의 React 포트.
// 계산 겹(감쇠 함수)은 useEffect 안에 있다: 펄스가 뜬 뒤 지난 시간(age)에 지수 감쇠식을 걸어
// 반지름은 PULSE_MAX_R 로 점근하고, 불투명도는 그 반지름 비율만큼 옅어진다.
import { useEffect, useRef, useState } from "react";
import styles from "./RadialPulse.module.scss";

type Box<T> = { current: T };

const STRINGS: Record<string, string> = { listening: "인증 대기 중", paused: "일시 정지됨" };

export default function RadialPulse() {
  const rootRef = useRef(null) as unknown as Box<HTMLButtonElement>;
  const ringRefs = useRef([]) as unknown as Box<SVGCircleElement[]>;
  const [status, setStatus] = useState(STRINGS.listening);
  const [pressed, setPressed] = useState(true);

  useEffect(() => {
    const PULSE_MAX_R = 40; // 변형 02: PULSE_MAX_R 40 → 70
    const TAU = 260;
    const LAUNCH_GAP = 550;
    const CUTOFF = TAU * 4.4;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const root = rootRef.current;
    const rings = ringRefs.current;
    if (!root || rings.length === 0) return;

    let isDemo = true;
    let listening = true;
    let slotCursor = 0;
    let lastLaunch = 0;
    let rafId = 0;
    const slots = rings.map((el) => ({ el, start: null as number | null }));

    function spawn(now: number) {
      const slot = slots[slotCursor % slots.length];
      slotCursor++;
      slot.start = now;
    }

    function tick() {
      for (let i = 0; i < slots.length; i++) {
        const slot = slots[i];
        if (slot.start === null) continue;
        const age = performance.now() - slot.start;
        if (age > CUTOFF) {
          slot.start = null;
          slot.el.style.opacity = "0";
          continue;
        }
        const radius = PULSE_MAX_R * (1 - Math.exp(-age / TAU));
        const opacity = Math.max(0, 1 - radius / PULSE_MAX_R);
        slot.el.setAttribute("r", radius.toFixed(2));
        slot.el.style.opacity = opacity.toFixed(3);
      }
    }

    function human() { if (isDemo) { root.classList.remove(styles.isDemo); isDemo = false; } }

    function toggle() {
      listening = !listening;
      setPressed(listening);
      setStatus(listening ? STRINGS.listening : STRINGS.paused);
    }

    function onClick() { human(); toggle(); }
    function onKeyDown(e: KeyboardEvent) { if (e.key === " " || e.key === "Enter") human(); }
    root.addEventListener("click", onClick);
    root.addEventListener("keydown", onKeyDown);

    function loop(ts: number) {
      const active = listening && (isDemo ? !reduce : true);
      if (active && ts - lastLaunch >= LAUNCH_GAP) {
        lastLaunch = ts;
        spawn(ts);
      }
      tick();
      rafId = requestAnimationFrame(loop);
    }
    rafId = requestAnimationFrame(loop);

    return () => {
      root.removeEventListener("click", onClick);
      root.removeEventListener("keydown", onKeyDown);
      cancelAnimationFrame(rafId);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.pulseWrap}>
        <button
          type="button"
          className={styles.pulse + " " + styles.isDemo}
          ref={rootRef}
          aria-pressed={pressed}
        >
          <svg className={styles.pulseIcon} viewBox="0 0 120 120" aria-hidden="true">
            {[0, 1, 2, 3].map((i) => (
              <circle
                key={i}
                className={styles.pulseRing}
                cx={60}
                cy={60}
                r={0}
                ref={(el: SVGCircleElement | null) => { if (el) ringRefs.current[i] = el; }}
              />
            ))}
            <circle className={styles.pulseCore} cx={60} cy={60} r={14} />
            <path className={styles.pulseMark} d="M52,64 A8 8 0 0 1 68,64" />
          </svg>
          <span className={styles.pulseLabel}>인증 대기</span>
        </button>
        <p className={styles.pulseStatus}>{status}</p>
      </div>
    </main>
  );
}