01Stacked box shadow

<main class="stage">
<div class="gen is-demo" id="gen">
  <div class="gen__top">
    <div class="gen__preview" aria-hidden="true"><span class="gen__chip">Card</span></div>
    <div class="gen__grid">
      <label class="gen__row">
        <span class="gen__lab">X</span>
        <span class="gen__slot">
          <input class="gen__rng" type="range" min="-24" max="24" step="2" value="0" data-var="--shadow-x" aria-label="Horizontal distance">
          <span class="gen__thumb" aria-hidden="true"></span>
        </span>
      </label>
      <label class="gen__row">
        <span class="gen__lab">Y</span>
        <span class="gen__slot">
          <input class="gen__rng" type="range" min="-24" max="24" step="2" value="10" data-var="--shadow-y" aria-label="Vertical distance">
          <span class="gen__thumb" aria-hidden="true"></span>
        </span>
      </label>
      <label class="gen__row">
        <span class="gen__lab">Blur</span>
        <span class="gen__slot">
          <input class="gen__rng" type="range" min="0" max="48" step="2" value="20" data-var="--shadow-blur" aria-label="Blur amount">
          <span class="gen__thumb" aria-hidden="true"></span>
        </span>
      </label>
      <label class="gen__row">
        <span class="gen__lab">Spread</span>
        <span class="gen__slot">
          <input class="gen__rng" type="range" min="-12" max="12" step="2" value="-4" data-var="--shadow-spread" aria-label="Spread amount">
          <span class="gen__thumb" aria-hidden="true"></span>
        </span>
      </label>
    </div>
  </div>
  <div class="gen__out">
    <code class="gen__code"><span class="gen__prop">box-shadow:</span> <span class="gen__v gen__v--x"></span>px <span class="gen__v gen__v--y"></span>px <span class="gen__v gen__v--blur"></span>px <span class="gen__v gen__v--spread"></span>px rgba(23,20,26,.34)</code>
    <button class="gen__copy" type="button" id="copy">Copy</button>
  </div>
</div>
</main>

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

// 그림자 겹쳐 쌓기 — 네 축을 사용자 지정 속성 네 개에 모으고, 미리보기 카드와 코드 상자가
// **같은 속성**을 읽는다. 슬라이더를 끌면 JS 가 속성을 갱신하고, 격자 미리보기(.is-demo)는
// 같은 속성을 CSS 키프레임으로 움직인다 — 그래서 손으로 만질 때와 자동 재생이 같은 그림이다.
// 네이티브 thumb 은 투명으로 두고 손잡이는 `.gen__thumb` 이 그린다. 값이 속성 하나라
// 자동 재생에서도 손잡이가 같이 움직인다 (input 의 value 는 CSS 로 못 움직인다).

$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-blue-deep;
$mono: ui-monospace, SFMono-Regular, "SF Mono", Consolas, "Liberation Mono", monospace;
$line: rgba(23, 20, 26, .14);
$track: rgba(23, 20, 26, .18);
$rail: 4px;
$thumb: 12px;

// 네 축을 정수로 등록한다. 등록해야 키프레임에서 보간되고 counter() 로도 읽힌다
@property --shadow-x { syntax: "<integer>"; inherits: true; initial-value: 0; }
@property --shadow-y { syntax: "<integer>"; inherits: true; initial-value: 10; }
@property --shadow-blur { syntax: "<integer>"; inherits: true; initial-value: 20; }
@property --shadow-spread { syntax: "<integer>"; inherits: true; initial-value: -4; }

@include stage($stage-paper);

.gen {
  min-width: 0;  // stage grid item 의 자동 최소폭(min-content) 을 끊는다 — BD9
  --shadow-x: 0;
  --shadow-y: 10;
  --shadow-blur: 20;
  --shadow-spread: -4;
  display: flex; flex-direction: column; gap: $sp-3;
  box-sizing: border-box; width: min(100%, 400px);
  padding: $sp-3; border: 1px solid $line; border-radius: $r-card;
  background: rgba(23, 20, 26, .04);
}

.gen__top { display: flex; align-items: center; gap: $sp-3; }

// ── 미리보기 — 네 속성을 그대로 box-shadow 로 읽는다
.gen__preview {
  flex: 0 0 auto;
  display: grid; place-items: center;
  box-sizing: border-box; width: 76px; height: 56px;
  border-radius: $r-control;
  background: $subject-cream;
  box-shadow:
    calc(var(--shadow-x) * 1px) calc(var(--shadow-y) * 1px) calc(var(--shadow-blur) * 1px) calc(var(--shadow-spread) * 1px) rgba(23, 20, 26, .34),
    calc(var(--shadow-x) * .5px) calc(var(--shadow-y) * .5px) calc(var(--shadow-blur) * .5px) 0 rgba(23, 20, 26, .22);
}
.gen__chip {
  color: $subject-ink;
  font-family: $mono; font-weight: 700; font-size: 11px; line-height: 1.4;
}

// ── 슬라이더 네 줄 (2열)
.gen__grid { flex: 1 1 auto; min-width: 0; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: $sp-1 $sp-2; }
.gen__row { display: flex; align-items: center; gap: $sp-1; cursor: pointer; }
.gen__lab {
  flex: 0 0 auto; width: 26px;
  color: $subject-ink;
  font-weight: 700; font-size: 10px; line-height: 1.4;
}
.gen__slot {
  position: relative; flex: 1 1 auto; min-width: 0;
  display: grid; align-items: center; height: 16px;
}
.gen__slot::before {
  content: ""; grid-area: 1 / 1;
  height: $rail; border-radius: $r-pill; background: $track;
}
.gen__rng {
  grid-area: 1 / 1; appearance: none; -webkit-appearance: none;
  width: 100%; min-width: 0; height: 16px; margin: 0; background: transparent;
  cursor: pointer;
}
.gen__rng::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: $thumb; height: $thumb; border: 0; border-radius: 50%;
  background: transparent;
}
.gen__rng::-moz-range-thumb {
  width: $thumb; height: $thumb; border: 0; border-radius: 50%;
  background: transparent;
}
.gen__rng:focus-visible { outline: 2px solid $color; outline-offset: 2px; border-radius: $r-pill; }

// 손잡이 — 값(사용자 지정 속성)에서 위치를 계산한다. 축마다 최소·최대가 달라 --pct 를 줄마다 준다
.gen__thumb {
  position: absolute; top: 50%; left: calc(var(--pct) * 1%);
  width: $thumb; height: $thumb; margin-top: -($thumb * .5); margin-left: -($thumb * .5);
  border-radius: 50%; background: $color;
  pointer-events: none;
}
.gen__row:nth-child(1) .gen__thumb { --pct: calc((var(--shadow-x) + 24) / 48 * 100); }
.gen__row:nth-child(2) .gen__thumb { --pct: calc((var(--shadow-y) + 24) / 48 * 100); }
.gen__row:nth-child(3) .gen__thumb { --pct: calc(var(--shadow-blur) / 48 * 100); }
.gen__row:nth-child(4) .gen__thumb { --pct: calc((var(--shadow-spread) + 12) / 24 * 100); }

// ── 코드 출력
.gen__out { display: flex; align-items: flex-start; gap: $sp-2; }
.gen__code {
  flex: 1 1 auto; min-width: 0;
  padding: $sp-2; border-radius: $r-sm;
  background: $subject-ink; color: $subject-cream;
  font-family: $mono; font-weight: 500; font-size: 10px; line-height: 1.5;
  white-space: nowrap; overflow: hidden;
}
.gen__prop { color: $subject-blue-light; }

// 코드 숫자는 counter() 로 그린다 — 속성이 곧 글자라 자동 재생에서도 숫자가 같이 바뀐다.
// textContent 로 쓰면 JS 가 도는 순간에만 바뀌어 미리보기 루프와 코드가 갈라진다
.gen__v { font-weight: 700; }
.gen__v--x::after { counter-reset: v var(--shadow-x); content: counter(v); }
.gen__v--y::after { counter-reset: v var(--shadow-y); content: counter(v); }
.gen__v--blur::after { counter-reset: v var(--shadow-blur); content: counter(v); }
.gen__v--spread::after { counter-reset: v var(--shadow-spread); content: counter(v); }
.gen__copy {
  flex: 0 0 auto;
  padding: $sp-2 $sp-3; border: 0; border-radius: $r-sm;
  background: $subject-blue-deep; color: $subject-cream;
  font-family: inherit; font-weight: 700; font-size: 11px; line-height: 1.4;
  cursor: pointer;
}
.gen__copy:focus-visible { outline: 2px solid $color; outline-offset: 2px; }

// ── 격자 미리보기 — 네 속성을 그대로 움직인다. 미리보기·손잡이·코드 숫자가 한 소스에서 나온다
@keyframes shadowX { 0%, 100% { --shadow-x: 0; } 30% { --shadow-x: -18; } 65% { --shadow-x: 16; } }
@keyframes shadowY { 0%, 100% { --shadow-y: 10; } 40% { --shadow-y: 24; } 80% { --shadow-y: 2; } }
@keyframes shadowBlur { 0%, 100% { --shadow-blur: 20; } 45% { --shadow-blur: 44; } 85% { --shadow-blur: 6; } }
@keyframes shadowSpread { 0%, 100% { --shadow-spread: -4; } 50% { --shadow-spread: 10; } }

.gen.is-demo {
  animation-name: shadowX, shadowY, shadowBlur, shadowSpread;
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}

@media (prefers-reduced-motion: reduce) {
  .gen.is-demo { animation: none !important; }
}

@media (max-width: 340px) {
  .gen { gap: $sp-2; padding: $sp-2; }
  .gen__top { gap: $sp-2; }
  .gen__preview { width: 64px; height: 48px; }
  .gen__code { font-size: 9px; }
}

@property --shadow-x {
  syntax: "<integer>";
  inherits: true;
  initial-value: 0;
}
@property --shadow-y {
  syntax: "<integer>";
  inherits: true;
  initial-value: 10;
}
@property --shadow-blur {
  syntax: "<integer>";
  inherits: true;
  initial-value: 20;
}
@property --shadow-spread {
  syntax: "<integer>";
  inherits: true;
  initial-value: -4;
}
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);
}

.gen {
  min-width: 0;
  --shadow-x: 0;
  --shadow-y: 10;
  --shadow-blur: 20;
  --shadow-spread: -4;
  display: flex;
  flex-direction: column;
  gap: 12px;
  box-sizing: border-box;
  width: min(100%, 400px);
  padding: 12px;
  border: 1px solid rgba(23, 20, 26, 0.14);
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.04);
}

.gen__top {
  display: flex;
  align-items: center;
  gap: 12px;
}

.gen__preview {
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  box-sizing: border-box;
  width: 76px;
  height: 56px;
  border-radius: 12px;
  background: #fff7e6;
  box-shadow: calc(var(--shadow-x) * 1px) calc(var(--shadow-y) * 1px) calc(var(--shadow-blur) * 1px) calc(var(--shadow-spread) * 1px) rgba(23, 20, 26, 0.34), calc(var(--shadow-x) * 0.5px) calc(var(--shadow-y) * 0.5px) calc(var(--shadow-blur) * 0.5px) 0 rgba(23, 20, 26, 0.22);
}

.gen__chip {
  color: #17141a;
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Consolas, "Liberation Mono", monospace;
  font-weight: 700;
  font-size: 11px;
  line-height: 1.4;
}

.gen__grid {
  flex: 1 1 auto;
  min-width: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 4px 8px;
}

.gen__row {
  display: flex;
  align-items: center;
  gap: 4px;
  cursor: pointer;
}

.gen__lab {
  flex: 0 0 auto;
  width: 26px;
  color: #17141a;
  font-weight: 700;
  font-size: 10px;
  line-height: 1.4;
}

.gen__slot {
  position: relative;
  flex: 1 1 auto;
  min-width: 0;
  display: grid;
  align-items: center;
  height: 16px;
}

.gen__slot::before {
  content: "";
  grid-area: 1/1;
  height: 4px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.18);
}

.gen__rng {
  grid-area: 1/1;
  appearance: none;
  -webkit-appearance: none;
  width: 100%;
  min-width: 0;
  height: 16px;
  margin: 0;
  background: transparent;
  cursor: pointer;
}

.gen__rng::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 12px;
  height: 12px;
  border: 0;
  border-radius: 50%;
  background: transparent;
}

.gen__rng::-moz-range-thumb {
  width: 12px;
  height: 12px;
  border: 0;
  border-radius: 50%;
  background: transparent;
}

.gen__rng:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
  border-radius: 999px;
}

.gen__thumb {
  position: absolute;
  top: 50%;
  left: calc(var(--pct) * 1%);
  width: 12px;
  height: 12px;
  margin-top: -6px;
  margin-left: -6px;
  border-radius: 50%;
  background: #0a4fe8;
  pointer-events: none;
}

.gen__row:nth-child(1) .gen__thumb {
  --pct: calc((var(--shadow-x) + 24) / 48 * 100);
}

.gen__row:nth-child(2) .gen__thumb {
  --pct: calc((var(--shadow-y) + 24) / 48 * 100);
}

.gen__row:nth-child(3) .gen__thumb {
  --pct: calc(var(--shadow-blur) / 48 * 100);
}

.gen__row:nth-child(4) .gen__thumb {
  --pct: calc((var(--shadow-spread) + 12) / 24 * 100);
}

.gen__out {
  display: flex;
  align-items: flex-start;
  gap: 8px;
}

.gen__code {
  flex: 1 1 auto;
  min-width: 0;
  padding: 8px;
  border-radius: 8px;
  background: #17141a;
  color: #fff7e6;
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Consolas, "Liberation Mono", monospace;
  font-weight: 500;
  font-size: 10px;
  line-height: 1.5;
  white-space: nowrap;
  overflow: hidden;
}

.gen__prop {
  color: #5b8cf8;
}

.gen__v {
  font-weight: 700;
}

.gen__v--x::after {
  counter-reset: v var(--shadow-x);
  content: counter(v);
}

.gen__v--y::after {
  counter-reset: v var(--shadow-y);
  content: counter(v);
}

.gen__v--blur::after {
  counter-reset: v var(--shadow-blur);
  content: counter(v);
}

.gen__v--spread::after {
  counter-reset: v var(--shadow-spread);
  content: counter(v);
}

.gen__copy {
  flex: 0 0 auto;
  padding: 8px 12px;
  border: 0;
  border-radius: 8px;
  background: #0a4fe8;
  color: #fff7e6;
  font-family: inherit;
  font-weight: 700;
  font-size: 11px;
  line-height: 1.4;
  cursor: pointer;
}

.gen__copy:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

@keyframes shadowX {
  0%, 100% {
    --shadow-x: 0;
  }
  30% {
    --shadow-x: -18;
  }
  65% {
    --shadow-x: 16;
  }
}
@keyframes shadowY {
  0%, 100% {
    --shadow-y: 10;
  }
  40% {
    --shadow-y: 24;
  }
  80% {
    --shadow-y: 2;
  }
}
@keyframes shadowBlur {
  0%, 100% {
    --shadow-blur: 20;
  }
  45% {
    --shadow-blur: 44;
  }
  85% {
    --shadow-blur: 6;
  }
}
@keyframes shadowSpread {
  0%, 100% {
    --shadow-spread: -4;
  }
  50% {
    --shadow-spread: 10;
  }
}
.gen.is-demo {
  animation-name: shadowX, shadowY, shadowBlur, shadowSpread;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@media (prefers-reduced-motion: reduce) {
  .gen.is-demo {
    animation: none !important;
  }
}
@media (max-width: 340px) {
  .gen {
    gap: 8px;
    padding: 8px;
  }
  .gen__top {
    gap: 8px;
  }
  .gen__preview {
    width: 64px;
    height: 48px;
  }
  .gen__code {
    font-size: 9px;
  }
}

var gen = document.getElementById('gen');
var copyBtn = document.getElementById('copy');
var ranges = Array.prototype.slice.call(gen.querySelectorAll('.gen__rng'));
var COPY_LABEL = 'Copy';
var DONE_LABEL = 'Copied';

// 슬라이더 값은 전부 gen 요소의 사용자 지정 속성 네 개에 모인다. 미리보기 카드의 box-shadow 도,
// 코드 상자의 숫자(counter() 로 그린다)도, 손잡이 위치도 같은 속성을 읽는다 — 그래서 자동 재생
// 루프가 속성만 움직여도 셋이 함께 바뀐다. JS 는 조작할 때 속성을 넣고 복사용 문자열만 만든다.
function readVar(name) {
  return parseInt(getComputedStyle(gen).getPropertyValue(name), 10) || 0;
}
function shadowText() {
  var x = readVar('--shadow-x'), y = readVar('--shadow-y');
  var blur = readVar('--shadow-blur'), spread = readVar('--shadow-spread');
  // 두 겹 중 아래 겹은 절반 거리·절반 번짐으로 깔아 깊이를 만든다
  return 'box-shadow: ' + x + 'px ' + y + 'px ' + blur + 'px ' + spread + 'px rgba(23,20,26,.34),\n'
    + '            ' + Math.round(x / 2) + 'px ' + Math.round(y / 2) + 'px ' + Math.round(blur / 2) + 'px 0 rgba(23,20,26,.22);';
}
ranges.forEach(function (input) {
  input.addEventListener('input', function () {
    gen.classList.remove('is-demo');
    gen.style.setProperty(input.dataset.var, input.value);
  });
  input.addEventListener('pointerdown', function () { gen.classList.remove('is-demo'); });
});
// 클립보드는 iframe·http 환경에서 막힐 수 있다. writeText 는 **거부된 프로미스**를 돌려주므로
// try/catch 로는 못 잡는다 — 반드시 catch 를 달아 선택 방식으로 떨어뜨린다 (조작 실측에서 잡았다)
function fallbackCopy(text) {
  var area = document.createElement('textarea');
  area.value = text;
  area.setAttribute('readonly', '');
  area.style.position = 'fixed';
  area.style.opacity = '0';
  document.body.appendChild(area);
  area.select();
  try { document.execCommand('copy'); } catch (err) { /* 여기까지 막히면 조용히 포기한다 */ }
  document.body.removeChild(area);
}
copyBtn.addEventListener('click', function () {
  gen.classList.remove('is-demo');
  var text = shadowText();
  if (navigator.clipboard && navigator.clipboard.writeText) {
    navigator.clipboard.writeText(text).catch(function () { fallbackCopy(text); });
  } else {
    fallbackCopy(text);
  }
  copyBtn.textContent = DONE_LABEL;
  setTimeout(function () { copyBtn.textContent = COPY_LABEL; }, 1200);
});

import { useState, useMemo } from 'react';
import styles from './ShadowStack.module.scss';

type Axis = { key: string; cssVar: string; label: string; min: number; max: number };
// ambient 선언에 React 이벤트 제네릭이 없어 로컬 타입으로 받는다 (blog-demo TS7006 항)
type RangeEvt = { target: { value: string } };

// 바닐라 판과 같은 네 축. 값은 사용자 지정 속성으로 내려보내고 미리보기·손잡이·코드가 함께 읽는다
const AXES: Axis[] = [
  { key: 'x', cssVar: '--shadow-x', label: '가로', min: -24, max: 24 },
  { key: 'y', cssVar: '--shadow-y', label: '세로', min: -24, max: 24 },
  { key: 'blur', cssVar: '--shadow-blur', label: '번짐', min: 0, max: 48 },
  { key: 'spread', cssVar: '--shadow-spread', label: '퍼짐', min: -12, max: 12 }
];

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

export default function ShadowStack({ duration = '2s', easing = 'cubic-bezier(.2, .8, .2, 1)', color = '#5b8cf8' }: ShadowStackProps) {
  const [values, setValues] = useState<Record<string, number>>({ x: 0, y: 10, blur: 20, spread: -4 });
  const [live, setLive] = useState(true);

  const codeText = useMemo(() => {
    const { x, y, blur, spread } = values;
    return `box-shadow: ${x}px ${y}px ${blur}px ${spread}px rgba(23,20,26,.34),\n            ${Math.round(x / 2)}px ${Math.round(y / 2)}px ${Math.round(blur / 2)}px 0 rgba(23,20,26,.22);`;
  }, [values]);

  const style = {
    '--dur-loop': duration,
    '--ease-spring': easing,
    '--accent': color,
    '--shadow-x': values.x,
    '--shadow-y': values.y,
    '--shadow-blur': values.blur,
    '--shadow-spread': values.spread
  } as Record<string, string | number>;

  function copy() {
    setLive(false);
    try {
      navigator.clipboard.writeText(codeText);
    } catch (err) {
      /* 클립보드가 막힌 환경에서는 조용히 넘어간다 */
    }
  }

  return (
    <div className={live ? `${styles.gen} ${styles.isDemo}` : styles.gen} style={style}>
      <div className={styles.top}>
        <div className={styles.preview} aria-hidden="true"><span className={styles.chip}>Card</span></div>
        <div className={styles.grid}>
          {AXES.map((axis) => (
            <label className={styles.row} key={axis.key}>
              <span className={styles.lab}>{axis.label}</span>
              <span className={styles.slot}>
                <input
                  className={styles.rng}
                  type="range"
                  min={axis.min}
                  max={axis.max}
                  step={2}
                  value={values[axis.key]}
                  aria-label={axis.label}
                  onChange={(e: RangeEvt) => {
                    setLive(false);
                    setValues((v) => ({ ...v, [axis.key]: Number(e.target.value) }));
                  }}
                />
                <span
                  className={styles.thumb}
                  aria-hidden="true"
                  style={{ left: `${((values[axis.key] - axis.min) / (axis.max - axis.min)) * 100}%` }}
                />
              </span>
            </label>
          ))}
        </div>
      </div>
      <div className={styles.out}>
        <code className={styles.code}>
          <span className={styles.prop}>box-shadow:</span> {values.x}px {values.y}px {values.blur}px {values.spread}px rgba(23,20,26,.34)
        </code>
        <button className={styles.copy} type="button" onClick={copy}>복사</button>
      </div>
    </div>
  );
}