03Cipher alphabet cycle

<main class="stage">
  <p class="ca-text" aria-live="polite">
    <span class="ca-c">U</span><span class="ca-c">N</span><span class="ca-c">L</span><span class="ca-c">O</span><span class="ca-c">C</span><span class="ca-c">K</span>
  </p>
</main>

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

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

@include stage($stage-orange);

.ca-text {
  margin: 0;
  display: flex;
  gap: 0;
  font: 800 clamp(24px, 8vw, 38px)/1.2 "Space Mono", "Courier New", monospace;
}

.ca-c {
  display: inline-block;
  min-width: 1ch;
  color: $color;
}

// 이 데모는 CSS keyframes 가 아니라 짧은 JS 로 각 글자를 알파벳 역순으로 되감아 원래 글자를 찾는다 —
// reduced-motion 은 스크립트 안의 matchMedia 체크로 처리한다 (index.html 참고)
@media (prefers-reduced-motion: reduce) {
  .ca-c { color: $color; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.ca-text {
  margin: 0;
  display: flex;
  gap: 0;
  font: 800 clamp(24px, 8vw, 38px)/1.2 "Space Mono", "Courier New", monospace;
}

.ca-c {
  display: inline-block;
  min-width: 1ch;
  color: #fff7e6;
}

@media (prefers-reduced-motion: reduce) {
  .ca-c {
    color: #fff7e6;
  }
}

var target = "UNLOCK";
  var spans = document.querySelectorAll(".ca-c");
  var reduced = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  var offs = [5, 6, 4, 7, 5, 6], cyc = 40;
  var n = 0;
  setInterval(function () {
    n++;
    spans.forEach(function (s, i) {
      var t = reduced ? 0 : (((n - i * 2) % cyc) + cyc) % cyc;
      var left = reduced ? 0 : Math.max(0, offs[i] - Math.floor(t / 2));
      var base = target.charCodeAt(i) - 65;
      s.textContent = String.fromCharCode(65 + (base + left) % 26);
    });
  }, 130);

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

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

// 실사용: 뷰포트에 들어오면 각 글자가 알파벳 몇 칸 뒤에서 한 칸씩 되감기며 원래 글자를 찾아간다. 다 맞으면 멈춘다.
export default function CipherAlphabetCycle({ text = "UNLOCK", interval = 130 }: CipherAlphabetCycleProps) {
  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; }
        const offs = text.split("").map((_, i) => 4 + ((i * 2) % 4));
        let n = 0;
        timer = setInterval(() => {
          n += 1;
          let done = true;
          let out = "";
          for (let i = 0; i < text.length; i++) {
            const left = Math.max(0, offs[i] - Math.floor(Math.max(0, n - i * 2) / 2));
            if (left > 0) done = false;
            const base = text.toUpperCase().charCodeAt(i) - 65;
            out += String.fromCharCode(65 + ((base + left) % 26));
          }
          setDisplay(out);
          if (done && 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>;
}