06Hologram flicker — a 2D noise value drives a subtle flicker-intensity value on the scan icon

<main class="stage">
<div class="holo-wrap">
<button type="button" class="holo is-demo" id="holo" aria-pressed="true">
  <svg class="holo__icon" viewBox="0 0 120 120" aria-hidden="true">
    <g id="glyph">
      <path class="holo__ridge" d="M20,90 A40 36 0 0 1 100,90"></path>
      <path class="holo__ridge" d="M30,90 A30 27 0 0 1 90,90"></path>
      <path class="holo__ridge" d="M40,90 A20 19 0 0 1 80,90"></path>
    </g>
    <rect class="holo__line" data-i="0" x="14" y="30" width="92" height="2"></rect>
    <rect class="holo__line" data-i="1" x="14" y="50" width="92" height="2"></rect>
    <rect class="holo__line" data-i="2" x="14" y="70" width="92" height="2"></rect>
    <rect class="holo__line" data-i="3" x="14" y="96" width="92" height="2"></rect>
  </svg>
  <span class="holo__label">Hologram auth badge</span>
</button>
<p class="holo__status" id="status">Projecting</p>
</div>
</main>

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

// 계산 겹은 index.html 의 noise() 에 있다 — 서로 다른 주기의 사인 3개를 가중합한 결정적 노이즈로
// 매 프레임 불투명도를 다시 계산한다(Math.random 미사용). 여기는 무대·모양만 맡는다.
@include stage($stage-ink);

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

.holo {
  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-sky; outline-offset: 4px; }
}

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

.holo__ridge {
  fill: none;
  stroke: $subject-sky;
  stroke-width: 2.5;
  stroke-linecap: round;
  filter: drop-shadow(0 0 5px rgba($subject-sky, .8));
}

.holo__line {
  fill: $subject-sky;
  opacity: .6;
}

.holo__label {
  color: $subject-cream;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: .02em;
}

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

@media (max-width: 340px) {
  .stage { padding: $sp-2; }
  .holo-wrap { gap: $sp-2; }
  .holo { padding: $sp-2 $sp-3; gap: $sp-2; }
  .holo__icon { width: 104px; }
  .holo__label { font-size: 12px; }
  .holo__status { font-size: 11px; }
}

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

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);
}

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

.holo {
  appearance: none;
  border: none;
  background: transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  padding: 16px;
  border-radius: 16px;
}
.holo:focus-visible {
  outline: 2px solid #6ec8ff;
  outline-offset: 4px;
}

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

.holo__ridge {
  fill: none;
  stroke: #6ec8ff;
  stroke-width: 2.5;
  stroke-linecap: round;
  filter: drop-shadow(0 0 5px rgba(110, 200, 255, 0.8));
}

.holo__line {
  fill: #6ec8ff;
  opacity: 0.6;
}

.holo__label {
  color: #fff7e6;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.2;
  letter-spacing: 0.02em;
}

.holo__status {
  margin: 0;
  color: rgba(255, 247, 230, 0.58);
  font-weight: 500;
  font-size: 12px;
  line-height: 1.2;
}

@media (max-width: 340px) {
  .stage {
    padding: 8px;
  }
  .holo-wrap {
    gap: 8px;
  }
  .holo {
    padding: 8px 12px;
    gap: 8px;
  }
  .holo__icon {
    width: 104px;
  }
  .holo__label {
    font-size: 12px;
  }
  .holo__status {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .holo__ridge, .holo__line {
    transition: none;
  }
}

(function () {
  // 계산 겹: 결정적 노이즈 플리커 — Math.random 없이 서로 다른 주기의 사인 3개를 가중합해
  // -1~1 노이즈 값을 만들고(노이즈 합성), 매 프레임 그 값으로 불투명도를 계산한다. 스캔 라인마다
  // 위상(phase)을 다르게 줘서 같은 순간에도 줄마다 다른 밝기로 반짝인다.
  var FREQS = [0.013, 0.031, 0.007]; // 세 사인의 각속도(rad/ms) — 서로소에 가깝게 골라 주기성이 안 보이게
  var WEIGHTS = [0.5, 0.32, 0.18];
  var PHASES = [0, 1.7, 3.4];
  var LINE_PHASE_STEP = 0.6; // 스캔 라인 인덱스마다 더하는 위상 차
  var BASE = 0.55, RANGE = 0.42;
  var WSUM = WEIGHTS[0] + WEIGHTS[1] + WEIGHTS[2];
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('holo');
  var glyph = document.getElementById('glyph');
  var lines = Array.prototype.slice.call(document.querySelectorAll('.holo__line'));
  var status = document.getElementById('status');
  var STRINGS = { on: 'Projecting', off: 'Power off' };
  var isDemo = true;
  var active = true;

  function noise(t, phaseOffset) {
    var v = 0;
    for (var i = 0; i < 3; i++) {
      v += WEIGHTS[i] * Math.sin(t * FREQS[i] + PHASES[i] + phaseOffset);
    }
    return v / WSUM;
  }

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

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

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

  function loop(ts) {
    var run = active && (isDemo ? !reduce : true);
    if (run) {
      glyph.style.opacity = (BASE + RANGE * noise(ts, 0)).toFixed(3);
      for (var i = 0; i < lines.length; i++) {
        var v = BASE + RANGE * noise(ts, i * LINE_PHASE_STEP + 1);
        lines[i].style.opacity = Math.max(0, Math.min(1, v)).toFixed(3);
      }
    } else {
      glyph.style.opacity = active ? '1' : '0.08';
      for (var j = 0; j < lines.length; j++) { lines[j].style.opacity = active ? '0.7' : '0'; }
    }
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// HologramFlicker — vanilla 판(run/371/demo/06-biometric-scan-hologram-flicker/index.html) 의 React 포트.
// 계산 겹(결정적 노이즈 플리커)은 useEffect 안에 있다: Math.random 없이 서로 다른 주기의 사인 3개를
// 가중합해 노이즈 값을 만들고, 매 프레임 그 값으로 불투명도를 계산한다.
import { useEffect, useRef, useState } from "react";
import styles from "./HologramFlicker.module.scss";

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

const STRINGS: Record<string, string> = { on: "투사 중", off: "전원 꺼짐" };

export default function HologramFlicker() {
  const rootRef = useRef(null) as unknown as Box<HTMLButtonElement>;
  const glyphRef = useRef(null) as unknown as Box<SVGGElement>;
  const lineRefs = useRef([]) as unknown as Box<SVGRectElement[]>;
  const [status, setStatus] = useState(STRINGS.on);
  const [pressed, setPressed] = useState(true);

  useEffect(() => {
    const FREQS = [0.013, 0.031, 0.007];
    const WEIGHTS = [0.5, 0.32, 0.18];
    const PHASES = [0, 1.7, 3.4];
    const LINE_PHASE_STEP = 0.6;
    const BASE = 0.55, RANGE = 0.42;
    const WSUM = WEIGHTS[0] + WEIGHTS[1] + WEIGHTS[2];
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const root = rootRef.current;
    const glyph = glyphRef.current;
    const lines = lineRefs.current;
    if (!root || !glyph || lines.length === 0) return;

    let isDemo = true;
    let active = true;
    let rafId = 0;

    function noise(t: number, phaseOffset: number) {
      let v = 0;
      for (let i = 0; i < 3; i++) {
        v += WEIGHTS[i] * Math.sin(t * FREQS[i] + PHASES[i] + phaseOffset);
      }
      return v / WSUM;
    }

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

    function toggle() {
      active = !active;
      setPressed(active);
      setStatus(active ? STRINGS.on : STRINGS.off);
    }

    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 run = active && (isDemo ? !reduce : true);
      if (run) {
        glyph.style.opacity = (BASE + RANGE * noise(ts, 0)).toFixed(3);
        for (let i = 0; i < lines.length; i++) {
          const v = BASE + RANGE * noise(ts, i * LINE_PHASE_STEP + 1);
          lines[i].style.opacity = Math.max(0, Math.min(1, v)).toFixed(3);
        }
      } else {
        glyph.style.opacity = active ? "1" : "0.08";
        for (let j = 0; j < lines.length; j++) lines[j].style.opacity = active ? "0.7" : "0";
      }
      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.holoWrap}>
        <button
          type="button"
          className={styles.holo + " " + styles.isDemo}
          ref={rootRef}
          aria-pressed={pressed}
        >
          <svg className={styles.holoIcon} viewBox="0 0 120 120" aria-hidden="true">
            <g ref={glyphRef}>
              <path className={styles.holoRidge} d="M20,90 A40 36 0 0 1 100,90" />
              <path className={styles.holoRidge} d="M30,90 A30 27 0 0 1 90,90" />
              <path className={styles.holoRidge} d="M40,90 A20 19 0 0 1 80,90" />
            </g>
            {[30, 50, 70, 96].map((y, i) => (
              <rect
                key={i}
                className={styles.holoLine}
                x={14}
                y={y}
                width={92}
                height={2}
                ref={(el: SVGRectElement | null) => { if (el) lineRefs.current[i] = el; }}
              />
            ))}
          </svg>
          <span className={styles.holoLabel}>홀로그램 인증표</span>
        </button>
        <p className={styles.holoStatus}>{status}</p>
      </div>
    </main>
  );
}