03Rotary dial knob

<main class="stage">
<div class="dk is-demo" id="dk">
  <div class="dk__ring" id="dkRing">
    <span class="dk__ticks" aria-hidden="true"></span>
    <span class="dk__arc" aria-hidden="true"></span>
    <span class="dk__needle" aria-hidden="true"></span>
    <div class="dk__knobWrap">
      <button class="dk__knob" id="dkKnob" type="button" role="slider" aria-label="Brightness dial"
        aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-valuetext="0%"></button>
    </div>
    <span class="dk__scaleMin" aria-hidden="true">0</span>
    <span class="dk__scaleMax" aria-hidden="true">100</span>
  </div>
  <div class="dk__side">
    <p class="dk__label">Brightness</p>
    <p class="dk__readout">
      <b class="dk__value" id="dkValue">0%</b>
      <span class="dk__demoDigits" aria-hidden="true"><i class="dk__digit dk__digit--0">0%</i><i class="dk__digit dk__digit--1">20%</i><i class="dk__digit dk__digit--2">40%</i><i class="dk__digit dk__digit--3">60%</i><i class="dk__digit dk__digit--4">80%</i><i class="dk__digit dk__digit--5">100%</i></span>
    </p>
    <p class="dk__hint">Drag or use arrow keys</p>
  </div>
</div>
</main>

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

// 회전 다이얼 노브 — 노브를 드래그해 돌리면 각도만큼 값이 오르내린다.
// 눈금 링은 repeating-conic-gradient(눈금 11개, 27도 간격), 진행 호는 conic-gradient 가
// --fill(0~1) 에 따라 채운다. 바늘과 노브 각인은 같은 각도로 돈다.
// role="slider" + aria-valuemin/max/now, 화살표 키·Home·End 지원. 드래그는 pointermove.
// 미리보기(.is-demo)는 노브가 좌우로 왕복 트는 것을 CSS 로 재생하고 값 글자는 steps(1,end) 컷.

// 진행 호를 애니메이션하려면 --fill 이 숫자로 등록되어 있어야 한다(262-08 실측 계열)
@property --fill {
  syntax: '<number>';
  inherits: true;
  initial-value: 0;
}

$duration: $dur-quick;
$easing: $ease-spring;
$color: $stage-paper;

@include stage($stage-orange);

.dk { display: flex; align-items: center; justify-content: center; gap: $sp-6; width: 100%; }

// ── 눈금 링 + 노브 ───────────────────────────────────────────
.dk__ring { position: relative; width: 168px; height: 168px; flex: 0 0 auto; }
.dk__ticks {
  position: absolute; inset: 0; border-radius: 50%;
  background: repeating-conic-gradient(from 224deg,
    rgba($subject-ink, .85) 0 1.6deg, rgba($subject-ink, 0) 1.6deg 27deg);
}
.dk__arc {
  position: absolute; inset: 7px; border-radius: 50%;
  background: conic-gradient(from 225deg,
    rgba($subject-ink, .82) 0 calc(var(--fill, 0) * 270deg),
    rgba($subject-ink, .10) calc(var(--fill, 0) * 270deg) 270deg,
    rgba($subject-ink, 0) 270deg 360deg);
}
.dk__needle { position: absolute; inset: 0; transform: rotate(calc(var(--angle, -135) * 1deg)); }
.dk__needle::before {
  content: ""; position: absolute; top: 2px; left: calc(50% - 2px); width: 4px; height: 14px;
  border-radius: $r-pill; background: $subject-ink;
}
.dk__knobWrap {
  position: absolute; inset: 30px; display: grid; place-items: center;
}
.dk__knob {
  position: relative; width: 108px; height: 108px; margin: 0; padding: 0; border: 0; border-radius: 50%;
  cursor: grab; touch-action: none; font-family: inherit;
  transform: rotate(calc(var(--angle, -135) * 1deg));
  transition: transform $duration $easing;
  background: repeating-conic-gradient(rgba($subject-ink, .24) 0 5deg, rgba($subject-ink, .05) 5deg 11deg),
    linear-gradient(145deg, rgba($subject-cream, .55), rgba($subject-ink, .28)), $color;
  box-shadow: 0 10px 18px rgba($subject-ink, .35), inset 0 2px 2px rgba($subject-cream, .55);
}
.dk__knob:active { cursor: grabbing; }
.dk__knob:focus-visible { outline: 2px solid $subject-ink; outline-offset: 3px; }
// 노브 얼굴 — 새김 눈금(위쪽 각인)은 ::after, 얼굴면은 ::before
.dk__knob::before {
  content: ""; position: absolute; inset: 10px; border-radius: 50%;
  background: linear-gradient(160deg, rgba($stage-paper, .95), rgba($subject-ink, .20)), $color;
  box-shadow: inset 0 -3px 8px rgba($subject-ink, .22), inset 0 2px 2px rgba($stage-paper, .8);
}
.dk__knob::after {
  content: ""; position: absolute; top: 8px; left: calc(50% - 2.5px); width: 5px; height: 26px;
  border-radius: $r-pill; background: $subject-ink;
}
.dk__scaleMin, .dk__scaleMax {
  position: absolute; top: 128px; font-weight: 800; font-size: 11px; line-height: 1; color: $subject-ink;
}
.dk__scaleMin { left: 2px; }
.dk__scaleMax { right: 2px; }

// ── 값 판 ────────────────────────────────────────────────────
.dk__side { display: flex; flex-direction: column; align-items: flex-start; gap: $sp-1; }
.dk__label {
  margin: 0; font-weight: 800; font-size: clamp(11px, 2.8vw, 13px); line-height: 1;
  letter-spacing: .22em; color: $subject-ink;
}
.dk__readout { position: relative; margin: 0; height: 44px; min-width: 108px; }
.dk__value {
  display: flex; align-items: center; font-weight: 800;
  font-size: clamp(28px, 7.5vw, 38px); line-height: 1; color: $subject-ink;
}
// 루프용 값 글자 — 정적 경로에서는 실제 값(.dk__value)이 자리를 지킨다
.dk__demoDigits { display: none; position: absolute; inset: 0; }
.dk__digit {
  position: absolute; inset: 0; display: flex; align-items: center;
  margin: 0; padding: 0; font-style: normal; font-weight: 800;
  font-size: clamp(28px, 7.5vw, 38px); line-height: 1; color: $subject-ink;
}
.dk__hint {
  margin: 0; font-weight: 700; font-size: clamp(9px, 2.4vw, 11px); line-height: 1.5;
  color: $subject-ink;
}

// ── 미리보기 루프(2초 한 바퀴) ────────────────────────────────
// 바늘·노브는 -135도 에서 135도 로 트고 돌아온다. 호(--fill)와 값 글자가 같은 시간표를 따른다.
.dk.is-demo .dk__needle, .dk.is-demo .dk__knob {
  animation-name: dkSweep; animation-duration: $dur-loop;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
@keyframes dkSweep {
  0%   { transform: rotate(-135deg); }
  45%  { transform: rotate(135deg); }
  50%  { transform: rotate(135deg); }
  95%  { transform: rotate(-135deg); }
  100% { transform: rotate(-135deg); }
}
.dk.is-demo {
  animation-name: dkFill; animation-duration: $dur-loop;
  animation-timing-function: linear; animation-iteration-count: infinite;
}
@keyframes dkFill {
  0%   { --fill: 0; }
  45%  { --fill: 1; }
  50%  { --fill: 1; }
  95%  { --fill: 0; }
  100% { --fill: 0; }
}
// 루프에서는 실제 값 글자를 비우고(공간은 유지) 6단계 값 글자가 컷으로 갈아 낀다
.dk.is-demo .dk__value { visibility: hidden; }
.dk.is-demo .dk__demoDigits { display: block; }
.dk.is-demo .dk__digit {
  opacity: 0;
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.dk.is-demo .dk__digit--0 { animation-name: dkDigit-0; }
.dk.is-demo .dk__digit--1 { animation-name: dkDigit-1; }
.dk.is-demo .dk__digit--2 { animation-name: dkDigit-2; }
.dk.is-demo .dk__digit--3 { animation-name: dkDigit-3; }
.dk.is-demo .dk__digit--4 { animation-name: dkDigit-4; }
.dk.is-demo .dk__digit--5 { animation-name: dkDigit-5; }
// 45% 까지 올라갔다 50% 부터 내려오는 트는 시간표에 맞춘 값 창(위 [9i, 9(i+1)) · 아래 (95-9(i+1), 95-9i])
@keyframes dkDigit-0 {
  0%   { opacity: 1; }
  9%   { opacity: 0; }
  86%  { opacity: 1; }
  100% { opacity: 1; }
}
@keyframes dkDigit-1 {
  0%   { opacity: 0; }
  9%   { opacity: 1; }
  18%  { opacity: 0; }
  77%  { opacity: 1; }
  86%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes dkDigit-2 {
  0%   { opacity: 0; }
  18%  { opacity: 1; }
  27%  { opacity: 0; }
  68%  { opacity: 1; }
  77%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes dkDigit-3 {
  0%   { opacity: 0; }
  27%  { opacity: 1; }
  36%  { opacity: 0; }
  59%  { opacity: 1; }
  68%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes dkDigit-4 {
  0%   { opacity: 0; }
  36%  { opacity: 1; }
  45%  { opacity: 0; }
  50%  { opacity: 1; }
  59%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes dkDigit-5 {
  0%   { opacity: 0; }
  45%  { opacity: 1; }
  50%  { opacity: 0; }
  100% { opacity: 0; }
}

@media (max-width: 340px) {
  .dk { gap: $sp-3; }
  .dk__ring { width: 128px; height: 128px; }
  .dk__arc { inset: 5px; }
  .dk__knobWrap { inset: 24px; }
  .dk__knob { width: 80px; height: 80px; }
  .dk__knob::after { height: 19px; top: 6px; }
  .dk__needle::before { height: 11px; }
  .dk__scaleMin, .dk__scaleMax { top: 98px; font-size: 9px; }
  .dk__readout { height: 36px; min-width: 84px; }
}

@media (prefers-reduced-motion: reduce) {
  .dk.is-demo .dk__needle { animation: none !important; transform: rotate(-135deg) !important; }
  .dk.is-demo .dk__knob { animation: none !important; transform: rotate(calc(var(--angle, -135) * 1deg)) !important; }
  .dk.is-demo { animation: none !important; --fill: 0 !important; }
  .dk.is-demo .dk__value { visibility: visible !important; }
  .dk.is-demo .dk__demoDigits { display: none !important; }
}

@property --fill {
  syntax: "<number>";
  inherits: true;
  initial-value: 0;
}
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);
}

.dk {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  width: 100%;
}

.dk__ring {
  position: relative;
  width: 168px;
  height: 168px;
  flex: 0 0 auto;
}

.dk__ticks {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  background: repeating-conic-gradient(from 224deg, rgba(23, 20, 26, 0.85) 0 1.6deg, rgba(23, 20, 26, 0) 1.6deg 27deg);
}

.dk__arc {
  position: absolute;
  inset: 7px;
  border-radius: 50%;
  background: conic-gradient(from 225deg, rgba(23, 20, 26, 0.82) 0 calc(var(--fill, 0) * 270deg), rgba(23, 20, 26, 0.1) calc(var(--fill, 0) * 270deg) 270deg, rgba(23, 20, 26, 0) 270deg 360deg);
}

.dk__needle {
  position: absolute;
  inset: 0;
  transform: rotate(calc(var(--angle, -135) * 1deg));
}

.dk__needle::before {
  content: "";
  position: absolute;
  top: 2px;
  left: calc(50% - 2px);
  width: 4px;
  height: 14px;
  border-radius: 999px;
  background: #17141a;
}

.dk__knobWrap {
  position: absolute;
  inset: 30px;
  display: grid;
  place-items: center;
}

.dk__knob {
  position: relative;
  width: 108px;
  height: 108px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  cursor: grab;
  touch-action: none;
  font-family: inherit;
  transform: rotate(calc(var(--angle, -135) * 1deg));
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
  background: repeating-conic-gradient(rgba(23, 20, 26, 0.24) 0 5deg, rgba(23, 20, 26, 0.05) 5deg 11deg), linear-gradient(145deg, rgba(255, 247, 230, 0.55), rgba(23, 20, 26, 0.28)), #ffffff;
  box-shadow: 0 10px 18px rgba(23, 20, 26, 0.35), inset 0 2px 2px rgba(255, 247, 230, 0.55);
}

.dk__knob:active {
  cursor: grabbing;
}

.dk__knob:focus-visible {
  outline: 2px solid #17141a;
  outline-offset: 3px;
}

.dk__knob::before {
  content: "";
  position: absolute;
  inset: 10px;
  border-radius: 50%;
  background: linear-gradient(160deg, rgba(255, 255, 255, 0.95), rgba(23, 20, 26, 0.2)), #ffffff;
  box-shadow: inset 0 -3px 8px rgba(23, 20, 26, 0.22), inset 0 2px 2px rgba(255, 255, 255, 0.8);
}

.dk__knob::after {
  content: "";
  position: absolute;
  top: 8px;
  left: calc(50% - 2.5px);
  width: 5px;
  height: 26px;
  border-radius: 999px;
  background: #17141a;
}

.dk__scaleMin, .dk__scaleMax {
  position: absolute;
  top: 128px;
  font-weight: 800;
  font-size: 11px;
  line-height: 1;
  color: #17141a;
}

.dk__scaleMin {
  left: 2px;
}

.dk__scaleMax {
  right: 2px;
}

.dk__side {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 4px;
}

.dk__label {
  margin: 0;
  font-weight: 800;
  font-size: clamp(11px, 2.8vw, 13px);
  line-height: 1;
  letter-spacing: 0.22em;
  color: #17141a;
}

.dk__readout {
  position: relative;
  margin: 0;
  height: 44px;
  min-width: 108px;
}

.dk__value {
  display: flex;
  align-items: center;
  font-weight: 800;
  font-size: clamp(28px, 7.5vw, 38px);
  line-height: 1;
  color: #17141a;
}

.dk__demoDigits {
  display: none;
  position: absolute;
  inset: 0;
}

.dk__digit {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  margin: 0;
  padding: 0;
  font-style: normal;
  font-weight: 800;
  font-size: clamp(28px, 7.5vw, 38px);
  line-height: 1;
  color: #17141a;
}

.dk__hint {
  margin: 0;
  font-weight: 700;
  font-size: clamp(9px, 2.4vw, 11px);
  line-height: 1.5;
  color: #17141a;
}

.dk.is-demo .dk__needle, .dk.is-demo .dk__knob {
  animation-name: dkSweep;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes dkSweep {
  0% {
    transform: rotate(-135deg);
  }
  45% {
    transform: rotate(135deg);
  }
  50% {
    transform: rotate(135deg);
  }
  95% {
    transform: rotate(-135deg);
  }
  100% {
    transform: rotate(-135deg);
  }
}
.dk.is-demo {
  animation-name: dkFill;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@keyframes dkFill {
  0% {
    --fill: 0;
  }
  45% {
    --fill: 1;
  }
  50% {
    --fill: 1;
  }
  95% {
    --fill: 0;
  }
  100% {
    --fill: 0;
  }
}
.dk.is-demo .dk__value {
  visibility: hidden;
}

.dk.is-demo .dk__demoDigits {
  display: block;
}

.dk.is-demo .dk__digit {
  opacity: 0;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.dk.is-demo .dk__digit--0 {
  animation-name: dkDigit-0;
}

.dk.is-demo .dk__digit--1 {
  animation-name: dkDigit-1;
}

.dk.is-demo .dk__digit--2 {
  animation-name: dkDigit-2;
}

.dk.is-demo .dk__digit--3 {
  animation-name: dkDigit-3;
}

.dk.is-demo .dk__digit--4 {
  animation-name: dkDigit-4;
}

.dk.is-demo .dk__digit--5 {
  animation-name: dkDigit-5;
}

@keyframes dkDigit-0 {
  0% {
    opacity: 1;
  }
  9% {
    opacity: 0;
  }
  86% {
    opacity: 1;
  }
  100% {
    opacity: 1;
  }
}
@keyframes dkDigit-1 {
  0% {
    opacity: 0;
  }
  9% {
    opacity: 1;
  }
  18% {
    opacity: 0;
  }
  77% {
    opacity: 1;
  }
  86% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes dkDigit-2 {
  0% {
    opacity: 0;
  }
  18% {
    opacity: 1;
  }
  27% {
    opacity: 0;
  }
  68% {
    opacity: 1;
  }
  77% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes dkDigit-3 {
  0% {
    opacity: 0;
  }
  27% {
    opacity: 1;
  }
  36% {
    opacity: 0;
  }
  59% {
    opacity: 1;
  }
  68% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes dkDigit-4 {
  0% {
    opacity: 0;
  }
  36% {
    opacity: 1;
  }
  45% {
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  59% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes dkDigit-5 {
  0% {
    opacity: 0;
  }
  45% {
    opacity: 1;
  }
  50% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@media (max-width: 340px) {
  .dk {
    gap: 12px;
  }
  .dk__ring {
    width: 128px;
    height: 128px;
  }
  .dk__arc {
    inset: 5px;
  }
  .dk__knobWrap {
    inset: 24px;
  }
  .dk__knob {
    width: 80px;
    height: 80px;
  }
  .dk__knob::after {
    height: 19px;
    top: 6px;
  }
  .dk__needle::before {
    height: 11px;
  }
  .dk__scaleMin, .dk__scaleMax {
    top: 98px;
    font-size: 9px;
  }
  .dk__readout {
    height: 36px;
    min-width: 84px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .dk.is-demo .dk__needle {
    animation: none !important;
    transform: rotate(-135deg) !important;
  }
  .dk.is-demo .dk__knob {
    animation: none !important;
    transform: rotate(calc(var(--angle, -135) * 1deg)) !important;
  }
  .dk.is-demo {
    animation: none !important;
    --fill: 0 !important;
  }
  .dk.is-demo .dk__value {
    visibility: visible !important;
  }
  .dk.is-demo .dk__demoDigits {
    display: none !important;
  }
}

var root = document.getElementById('dk');
var ring = document.getElementById('dkRing');
var knob = document.getElementById('dkKnob');
var valueEl = document.getElementById('dkValue');
var MIN = -135, MAX = 135; // 도(°). 0도는 정위(12시 방향)
var VAL_TEXT = '{v}%';
var value = 0;
var dragging = false;

function apply() {
  var angle = MIN + (MAX - MIN) * value / 100; // 백분율 값을 각도로
  root.style.setProperty('--angle', String(Math.round(angle)));
  root.style.setProperty('--fill', (value / 100).toFixed(3));
  knob.setAttribute('aria-valuenow', String(value));
  knob.setAttribute('aria-valuetext', VAL_TEXT.replace('{v}', String(value)));
  valueEl.textContent = value + '%';
}
function angleOf(x, y) {
  var r = ring.getBoundingClientRect();
  var cx = r.left + r.width / 2, cy = r.top + r.height / 2;
  var deg = Math.atan2(x - cx, cy - y) * 180 / Math.PI; // 정위가 0도, 시계 방향이 양수
  return Math.max(MIN, Math.min(MAX, deg));
}
knob.addEventListener('pointerdown', function (e) {
  root.classList.remove('is-demo');
  dragging = true;
  knob.setPointerCapture(e.pointerId);
  value = Math.round((angleOf(e.clientX, e.clientY) - MIN) / (MAX - MIN) * 100);
  apply();
});
knob.addEventListener('pointermove', function (e) {
  if (!dragging) { root.classList.remove('is-demo'); return; }
  value = Math.round((angleOf(e.clientX, e.clientY) - MIN) / (MAX - MIN) * 100);
  apply();
});
knob.addEventListener('pointerup', function () { dragging = false; });
knob.addEventListener('pointercancel', function () { dragging = false; });
knob.addEventListener('keydown', function (e) {
  var step = e.shiftKey ? 10 : 5;
  if (e.key === 'ArrowRight' || e.key === 'ArrowUp') { value = Math.min(100, value + step); }
  else if (e.key === 'ArrowLeft' || e.key === 'ArrowDown') { value = Math.max(0, value - step); }
  else if (e.key === 'Home') { value = 0; }
  else if (e.key === 'End') { value = 100; }
  else { return; }
  e.preventDefault();
  root.classList.remove('is-demo');
  apply();
});
apply();

// DialKnob — vanilla 판(run/013/demo/03-skeuo-dial-knob/index.html) 의 React 포트.
// 노브를 드래그해 돌리면 각도만큼 값이 오르내리고 눈금 링의 바늘이 따라 섭니다.
// role="slider" + aria-valuemin/max/now, 화살표 키·Home·End 지원. 값·키프레임은 vanilla 와 같다.
// 이벤트 제네릭 대신 로컬 타입으로 선언한다(ambient 타입만 있어 implicit any 를 피한다).
import { useRef, useState } from "react";
import styles from "./DialKnob.module.scss";

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

type Vars = { [k: string]: any };
type PtrEvt = {
  clientX: number;
  clientY: number;
  pointerId: number;
  currentTarget: { setPointerCapture: (id: number) => void };
};
type KeyEvt = { key: string; shiftKey: boolean; preventDefault: () => void };

const MIN = -135; // 도(°). 0도는 정위(12시 방향)
const MAX = 135;
const KNOB_LABEL = "밝기 조절 다이얼";
const LABEL_TEXT = "밝기";
const HINT_TEXT = "드래그나 화살표 키로 조절";
const VAL_TEXT = "{v}퍼센트";
const DIGITS = ["0%", "20%", "40%", "60%", "80%", "100%"];

export default function DialKnob({
  duration = 220,
  easing = "cubic-bezier(.2, .8, .2, 1)", // = $ease-spring
  color = "#ffffff",
}: DialKnobProps) {
  const [value, setValue] = useState(0);
  const [demo, setDemo] = useState(true);
  const ringRef = useRef<HTMLDivElement | null>(null);
  const dragging = useRef(false);

  const angle = Math.round(MIN + (MAX - MIN) * value / 100); // 백분율 값을 각도로
  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
    "--angle": String(angle),
    "--fill": (value / 100).toFixed(3),
  };
  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");

  function angleOf(x: number, y: number): number {
    const el = ringRef.current;
    if (!el) { return MIN; }
    const r = el.getBoundingClientRect();
    const cx = r.left + r.width / 2;
    const cy = r.top + r.height / 2;
    const deg = Math.atan2(x - cx, cy - y) * 180 / Math.PI; // 정위가 0도, 시계 방향이 양수
    return Math.max(MIN, Math.min(MAX, deg));
  }
  function valueAt(x: number, y: number): number {
    return Math.round((angleOf(x, y) - MIN) / (MAX - MIN) * 100);
  }
  function onPointerDown(e: PtrEvt) {
    setDemo(false);
    dragging.current = true;
    e.currentTarget.setPointerCapture(e.pointerId);
    setValue(valueAt(e.clientX, e.clientY));
  }
  function onPointerMove(e: PtrEvt) {
    if (!dragging.current) {
      setDemo(false);
      return;
    }
    setValue(valueAt(e.clientX, e.clientY));
  }
  function onPointerUp() {
    dragging.current = false;
  }
  function onKeyDown(e: KeyEvt) {
    const step = e.shiftKey ? 10 : 5;
    if (e.key === "ArrowRight" || e.key === "ArrowUp") {
      setValue((v) => Math.min(100, v + step));
    } else if (e.key === "ArrowLeft" || e.key === "ArrowDown") {
      setValue((v) => Math.max(0, v - step));
    } else if (e.key === "Home") {
      setValue(0);
    } else if (e.key === "End") {
      setValue(100);
    } else {
      return;
    }
    e.preventDefault();
    setDemo(false);
  }

  return (
    <main className={styles.stage}>
      <div className={cls} style={vars}>
        <div className={styles.ring} ref={ringRef}>
          <span className={styles.ticks} aria-hidden="true"></span>
          <span className={styles.arc} aria-hidden="true"></span>
          <span className={styles.needle} aria-hidden="true"></span>
          <div className={styles.knobWrap}>
            <button
              className={styles.knob}
              type="button"
              role="slider"
              aria-label={KNOB_LABEL}
              aria-valuemin={0}
              aria-valuemax={100}
              aria-valuenow={value}
              aria-valuetext={VAL_TEXT.replace("{v}", String(value))}
              onPointerDown={onPointerDown}
              onPointerMove={onPointerMove}
              onPointerUp={onPointerUp}
              onPointerCancel={onPointerUp}
              onKeyDown={onKeyDown}
            ></button>
          </div>
          <span className={styles.scaleMin} aria-hidden="true">0</span>
          <span className={styles.scaleMax} aria-hidden="true">100</span>
        </div>
        <div className={styles.side}>
          <p className={styles.label}>{LABEL_TEXT}</p>
          <p className={styles.readout}>
            <b className={styles.value}>{value}%</b>
            <span className={styles.demoDigits} aria-hidden="true">
              {DIGITS.map((d, i) => (
                <i className={`${styles.digit} ${styles["digit" + String(i)]}`} key={d}>{d}</i>
              ))}
            </span>
          </p>
          <p className={styles.hint}>{HINT_TEXT}</p>
        </div>
      </div>
    </main>
  );
}