06Scramble decode

<main class="stage">
  <p class="sd-text" id="sd" aria-live="polite">DECODE</p>
</main>

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

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

@include stage($stage-yellow);

.sd-text {
  margin: 0;
  font: 800 clamp(28px, 9vw, 44px)/1.2 "Space Mono", "Courier New", monospace;
  letter-spacing: .06em;
  color: $color;
}

// 이 데모는 CSS keyframes 가 아니라 짧은 JS(setInterval)로 글자를 무작위로 바꾼다 —
// 그래서 reduced-motion 은 CSS 가 아니라 스크립트 안의 matchMedia 체크로 처리한다 (index.html 참고)
@media (prefers-reduced-motion: reduce) {
  .sd-text { color: $color; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sd-text {
  margin: 0;
  font: 800 clamp(28px, 9vw, 44px)/1.2 "Space Mono", "Courier New", monospace;
  letter-spacing: 0.06em;
  color: #17141a;
}

@media (prefers-reduced-motion: reduce) {
  .sd-text {
    color: #17141a;
  }
}

var target = "DECODE";
  var glyphs = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  var el = document.getElementById("sd");
  var reduced = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  function tick(locked) {
    if (reduced) { el.textContent = target; return; }
    var out = "";
    for (var i = 0; i < target.length; i++) {
      out += i < locked ? target[i] : glyphs[Math.floor(Math.random() * glyphs.length)];
    }
    el.textContent = out;
  }
  var frame = 0;
  setInterval(function () {
    frame++;
    var locked = Math.max(0, Math.floor((frame % 26) / 3) - 2);
    tick(Math.min(locked, target.length));
  }, 60);

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

export interface ScrambleDecodeProps {
  text?: string;
  interval?: number;
}

const GLYPHS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

// 실사용: 뷰포트에 들어오면 무작위 글자가 바뀌다가 왼쪽부터 한 번씩 진짜 글자로 잠긴다. 다 풀리면 멈춘다.
export default function ScrambleDecode({ text = "DECODE", interval = 40 }: ScrambleDecodeProps) {
  const ref = useRef<HTMLParagraphElement>(null);
  const [display, setDisplay] = useState(text);

  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) { setDisplay(text); return; }
        let frame = 0;
        timer = setInterval(() => {
          frame += 1;
          const locked = Math.min(Math.max(0, Math.floor(frame / 3) - 2), text.length);
          let out = "";
          for (let i = 0; i < text.length; i++) {
            out += i < locked ? text[i] : GLYPHS[Math.floor(Math.random() * GLYPHS.length)];
          }
          setDisplay(out);
          if (locked >= text.length && timer) { clearInterval(timer); timer = null; }
        }, interval);
      });
    }, { threshold: 0.3 });
    io.observe(el);
    return () => { io.disconnect(); if (timer) clearInterval(timer); };
  }, [text, interval]);

  return (
    <p ref={ref} className={styles.text} aria-live="polite">{display}</p>
  );
}