01Loader Whose Hexahedron Advances a Face Each Time Percent Crosses a Threshold

<main class="stage">
<div class="ld" id="ld">
  <p class="ld__hint">Click or press the space bar to pause or restart</p>
  <div class="ld__field" id="field" role="application" aria-label="Cube face-swap progress test panel" tabindex="0">
    <div class="c3__scene">
      <div class="c3__cube" id="c3cube">
        <div class="c3__face c3__face--front">1</div>
        <div class="c3__face c3__face--right">2</div>
        <div class="c3__face c3__face--back">3</div>
        <div class="c3__face c3__face--left">4</div>
      </div>
    </div>
    <b class="ld__badge" aria-hidden="true"><span class="ld__badgeNum" id="pct">0%</span><span class="ld__badgeUnit">Progress</span></b>
  </div>
</div>
</main>

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

// 정육면체 면 전환 로더 — 진행률(0~1)을 문턱 목록과 비교해 넘은 문턱 수만큼 큐브를 90deg 씩 돌리고,
// 매 프레임 화가 알고리즘(면 법선 각 + 현재 회전각의 cos)으로 z-index 를 다시 매긴다.
// 395(캔버스 rAF 물리)·393(포인터 tilt) 과 다른 축 — CSS perspective/preserve-3d 위에 문턱·깊이정렬 계산을 얹는다.

$duration: $dur-loop;
$easing: linear;
$color: $subject-blue-deep;

@include stage($stage-ink);

.ld {
  display: flex; flex-direction: column; gap: $sp-2;
  width: 100%; max-width: 360px;
}

.ld__hint {
  margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: rgba($subject-cream, .78);
  text-align: center;
}

.ld__field {
  position: relative; height: 208px;
  border-radius: $r-card; overflow: hidden;
  background: $subject-cream;
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  display: grid; place-items: center;
  cursor: pointer;
}
.ld__field:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }

.c3__scene {
  perspective: clamp(280px, 60vw, 420px);
}

.c3__cube {
  position: relative;
  width: 92px; height: 92px;
  transform-style: preserve-3d;
}

.c3__face {
  position: absolute; inset: 0;
  display: grid; place-items: center;
  border-radius: $r-sm;
  font-weight: 700; font-size: 26px; line-height: 1;
  color: $subject-cream;
  background: $color;
  backface-visibility: hidden;
  box-shadow: $shadow-press;
}
.c3__face--front { transform: translateZ(46px); }
.c3__face--right { transform: rotateY(90deg) translateZ(46px); background: darken($color, 8%); }
.c3__face--back  { transform: rotateY(180deg) translateZ(46px); }
.c3__face--left  { transform: rotateY(-90deg) translateZ(46px); background: darken($color, 8%); }

.ld__badge {
  position: absolute; right: $sp-2; top: $sp-2;
  display: flex; align-items: baseline; gap: $sp-1;
  padding: $sp-1 $sp-2; border-radius: $r-pill;
  background: rgba($subject-ink, .78);
  color: $subject-cream; font-weight: 700; font-size: 11px;
}
.ld__badgeNum { font-size: 13px; color: $stage-yellow; }
.ld__badgeUnit { font-weight: 700; }

@media (max-width: 340px) {
  .ld { gap: $sp-1; }
  .ld__field { height: 124px; }
  .c3__cube { width: 64px; height: 64px; }
  .c3__face--front, .c3__face--back { transform: translateZ(32px); }
  .c3__face--right { transform: rotateY(90deg) translateZ(32px); background: darken($color, 8%); }
  .c3__face--left { transform: rotateY(-90deg) translateZ(32px); background: darken($color, 8%); }
  .c3__face--back { transform: rotateY(180deg) translateZ(32px); }
  .ld__badge { font-size: 10px; padding: 0 $sp-1; }
  .ld__badgeNum { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field { cursor: default !important; }
  .ld.is-still .ld__badge { opacity: .92 !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);
}

.ld {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 360px;
}

.ld__hint {
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: rgba(255, 247, 230, 0.78);
  text-align: center;
}

.ld__field {
  position: relative;
  height: 208px;
  border-radius: 16px;
  overflow: hidden;
  background: #fff7e6;
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  display: grid;
  place-items: center;
  cursor: pointer;
}

.ld__field:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.c3__scene {
  perspective: clamp(280px, 60vw, 420px);
}

.c3__cube {
  position: relative;
  width: 92px;
  height: 92px;
  transform-style: preserve-3d;
}

.c3__face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: 8px;
  font-weight: 700;
  font-size: 26px;
  line-height: 1;
  color: #fff7e6;
  background: #0a4fe8;
  backface-visibility: hidden;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}

.c3__face--front {
  transform: translateZ(46px);
}

.c3__face--right {
  transform: rotateY(90deg) translateZ(46px);
  background: rgb(3.2604116027%, 25.757251661%, 75.6415491817%);
}

.c3__face--back {
  transform: rotateY(180deg) translateZ(46px);
}

.c3__face--left {
  transform: rotateY(-90deg) translateZ(46px);
  background: rgb(3.2604116027%, 25.757251661%, 75.6415491817%);
}

.ld__badge {
  position: absolute;
  right: 8px;
  top: 8px;
  display: flex;
  align-items: baseline;
  gap: 4px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff7e6;
  font-weight: 700;
  font-size: 11px;
}

.ld__badgeNum {
  font-size: 13px;
  color: #ffd23f;
}

.ld__badgeUnit {
  font-weight: 700;
}

@media (max-width: 340px) {
  .ld {
    gap: 4px;
  }
  .ld__field {
    height: 124px;
  }
  .c3__cube {
    width: 64px;
    height: 64px;
  }
  .c3__face--front, .c3__face--back {
    transform: translateZ(32px);
  }
  .c3__face--right {
    transform: rotateY(90deg) translateZ(32px);
    background: rgb(3.2604116027%, 25.757251661%, 75.6415491817%);
  }
  .c3__face--left {
    transform: rotateY(-90deg) translateZ(32px);
    background: rgb(3.2604116027%, 25.757251661%, 75.6415491817%);
  }
  .c3__face--back {
    transform: rotateY(180deg) translateZ(32px);
  }
  .ld__badge {
    font-size: 10px;
    padding: 0 4px;
  }
  .ld__badgeNum {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field {
    cursor: default !important;
  }
  .ld.is-still .ld__badge {
    opacity: 0.92 !important;
  }
}

(function () {
'use strict';
var root = document.getElementById('ld');
var field = document.getElementById('field');
var pctEl = document.getElementById('pct');
var cube = document.getElementById('c3cube');
var faces = Array.prototype.slice.call(cube.querySelectorAll('.c3__face'));
var NORMALS = [0, 90, 180, 270]; // front·right·back·left 면 법선 각

var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
var LOOP = 2;          // 로더 한 바퀴(초) — 캡처 창(2초)의 약수라 gif 가 끊기지 않는다
var REDUCE_P = 0.7;
var FACE_THRESHOLD = 25; // 면 하나를 넘길 진행률 문턱(%) — 변형 01 대상
var t0 = 0, raf = 0, paused = false, lastP = 0;

// 화가 알고리즘 — 각 면의 (법선각 + 현재 회전각) 코사인을 깊이로 써서 뒤에서 앞 순서로 z-index 를 매긴다.
function depthSort(rotY) {
  var withDepth = faces.map(function (el, i) {
    return { el: el, depth: Math.cos((NORMALS[i] + rotY) * Math.PI / 180) };
  });
  withDepth.sort(function (a, b) { return a.depth - b.depth; });
  withDepth.forEach(function (o, idx) { o.el.style.zIndex = String(idx); });
}

function render(p) {
  lastP = p;
  var pct = Math.round(p * 100);
  var idx = Math.min(faces.length - 1, Math.floor(pct / FACE_THRESHOLD));
  var rotY = idx * 90;
  cube.style.transform = 'rotateY(' + rotY + 'deg)';
  depthSort(rotY);
  pctEl.textContent = pct + '%';
}

function frame(now) {
  if (!paused) { var t = (now - t0) / 1000; render((t % LOOP) / LOOP); }
  raf = requestAnimationFrame(frame);
}
function togglePause() {
  paused = !paused;
  root.classList.toggle('is-paused', paused);
  render(reduce ? REDUCE_P : lastP);
}
function restart() {
  t0 = performance.now();
  render(reduce ? REDUCE_P : 0);
}

field.addEventListener('click', function () { togglePause(); });
field.addEventListener('keydown', function (e) {
  if (e.key === ' ' || e.key === 'Enter') { e.preventDefault(); togglePause(); }
  else if (e.key === 'r' || e.key === 'R') { e.preventDefault(); restart(); }
});
window.addEventListener('resize', function () {
  if (paused || reduce) render(reduce ? REDUCE_P : lastP);
});

t0 = performance.now();
if (reduce) {
  root.classList.add('is-still');
  render(REDUCE_P);
} else {
  raf = requestAnimationFrame(frame);
}
})();

// CubeFaceSwap — vanilla 판(run/399/demo/01-loader-3d-cube-face-percent-swap/index.html) 의 React 포트.
// 진행률(0~1)이 FACE_THRESHOLD 문턱을 넘을 때마다 큐브를 90deg 돌리고, 매 프레임 화가 알고리즘
// (면 법선 각 + 현재 회전각의 cos) 으로 z-index 를 다시 매긴다. 움직임은 rAF 루프가 다 계산하므로
// @keyframes 가 없다 — props 는 CSS 변수로 내려간다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./CubeFaceSwap.module.scss";

export type CubeFaceSwapProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };

const NORMALS = [0, 90, 180, 270]; // front·right·back·left 면 법선 각
const LOOP = 2;           // 로더 한 바퀴(초) — 캡처 창(2초)의 약수라 gif 가 끊기지 않는다
const REDUCE_P = 0.7;
const FACE_THRESHOLD = 25; // 면 하나를 넘길 진행률 문턱(%) — 변형 01 대상
const FIELD_LABEL = "정육면체 면 전환 진행 실험판";

export default function CubeFaceSwap({
  duration = "2s",                             // vanilla LOOP
  easing = "linear",                           // vanilla $easing
  color = "#0a4fe8",                           // vanilla $color: $subject-blue-deep
}: CubeFaceSwapProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const cubeRef = useRef<HTMLDivElement | null>(null);
  const pctRef = useRef<HTMLSpanElement | null>(null);
  const facesRef = useRef<HTMLDivElement[]>([]) as Box<HTMLDivElement[]>;
  const pausedRef = useRef(false) as Box<boolean>;
  const lastPRef = useRef(0) as Box<number>;
  const t0Ref = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  // 화가 알고리즘 — 각 면의 (법선각 + 현재 회전각) 코사인을 깊이로 써서 뒤에서 앞 순서로 z-index 를 매긴다.
  function depthSort(rotY: number): void {
    const faces = facesRef.current;
    const withDepth = faces.map((el, i) => ({ el, depth: Math.cos((NORMALS[i] + rotY) * Math.PI / 180) }));
    withDepth.sort((a, b) => a.depth - b.depth);
    withDepth.forEach((o, idx) => { o.el.style.zIndex = String(idx); });
  }

  function render(p: number): void {
    lastPRef.current = p;
    const pct = Math.round(p * 100);
    const faces = facesRef.current;
    const idx = Math.min(faces.length - 1, Math.floor(pct / FACE_THRESHOLD));
    const rotY = idx * 90;
    const cube = cubeRef.current;
    if (cube) cube.style.transform = "rotateY(" + rotY + "deg)";
    depthSort(rotY);
    if (pctRef.current) pctRef.current.textContent = pct + "%";
  }

  function togglePause(): void {
    pausedRef.current = !pausedRef.current;
    const root = rootRef.current;
    if (root) root.classList.toggle("is-paused", pausedRef.current);
    render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function restart(): void {
    t0Ref.current = performance.now();
    render(reduced() ? REDUCE_P : 0);
  }

  function onKey(e: KeyEvt): void {
    if (e.key === " " || e.key === "Enter") { e.preventDefault(); togglePause(); }
    else if (e.key === "r" || e.key === "R") { e.preventDefault(); restart(); }
  }

  function onClick(): void {
    togglePause();
  }

  function onResize(): void {
    if (pausedRef.current || reduced()) render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function frame(now: number): void {
    if (!pausedRef.current) {
      const t = (now - t0Ref.current) / 1000;
      render((t % LOOP) / LOOP);
    }
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const cube = cubeRef.current;
    if (cube) facesRef.current = Array.prototype.slice.call(cube.children) as HTMLDivElement[];
    t0Ref.current = performance.now();
    window.addEventListener("resize", onResize);
    if (reduced()) {
      const root = rootRef.current;
      if (root) root.classList.add("is-still");
      render(REDUCE_P);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.root} ref={rootRef} style={vars}>
        <p className={styles.hint}>클릭하거나 스페이스바를 누르면 멈추거나 다시 갑니다</p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onClick={onClick}
          onKeyDown={onKey}
        >
          <div className={styles.scene}>
            <div className={styles.cube} ref={cubeRef}>
              <div className={styles.face + " " + styles.faceFront}>1</div>
              <div className={styles.face + " " + styles.faceRight}>2</div>
              <div className={styles.face + " " + styles.faceBack}>3</div>
              <div className={styles.face + " " + styles.faceLeft}>4</div>
            </div>
          </div>
          <b className={styles.badge} aria-hidden="true"><span className={styles.badgeNum} ref={pctRef}>0%</span><span className={styles.badgeUnit}>진행</span></b>
        </div>
      </div>
    </main>
  );
}