05A Dial Whose Needle Bounces at Every Tick Mark While the Swept Sector Fills In

<main class="stage">
  <div class="cd is-demo" id="cd" data-demo="1">
    <div class="cd__view cd__view--dial">
      <div class="cd__face" data-r="face" role="img" aria-label="A dial that bounces on every tick">
        <div class="cd__sector" data-r="sector"></div>
        <div class="cd__needle" data-r="needle"></div>
        <i class="cd__hub"></i>
      </div>
      <p class="cd__read cd__read--center" role="timer"><b data-r="num">10</b><span>s</span></p>
    </div>
    <div class="cd__bar">
      <button class="cd__btn" type="button" data-r="toggle">Pause</button>
      <button class="cd__btn" type="button" data-r="reset">Reset</button>
    </div>
    <p class="cd__sr" aria-live="polite" data-r="status"></p>
  </div>
</main>

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

// 핵심: 남은 시간 하나(경과는 rAF 타임스탬프 누적)에서 모양을 계산해 그린다. CSS 는 모양과 색만 맡는다.

$bg: $stage-paper;
$fg: $subject-ink;
$btn: rgba($subject-ink, .1);
@include stage($bg);
.cd {
  --view-h: min(calc(100vh - 2 * clamp(8px, 4vw, 24px) - 48px), 196px);
  position: relative;
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  color: $fg;
  font-size: 14px;
  line-height: 20px;
  font-weight: 600;
}
.cd__view { position: relative; }
.cd__view--scene { width: 100%; height: var(--view-h); overflow: hidden; border-radius: $r-card; background: mix($stage-ink, $subject-lilac, 88%); }
.cd__cv { display: block; width: 100%; height: 100%; }
.cd__read { margin: 0; display: flex; align-items: baseline; gap: $sp-1; font-variant-numeric: tabular-nums; }
.cd__read b { font-size: 28px; line-height: 32px; font-weight: 800; }
.cd__read--center { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); }
.cd__read--corner { position: absolute; left: $sp-2; top: $sp-2; }
.cd__bar { display: flex; gap: $sp-2; }
.cd__btn {
  box-sizing: border-box;
  height: 36px;
  padding: 0 $sp-4;
  border: 0;
  border-radius: $r-control;
  background: $btn;
  color: $fg;
  font-size: 14px;
  line-height: 20px;
  font-weight: 700;
  cursor: pointer;
}
.cd__btn:focus-visible { outline: 2px solid $subject-lilac; outline-offset: 2px; }
.cd__sr { position: absolute; width: 1px; height: 1px; margin: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
@media (prefers-reduced-motion: reduce) {
  .cd__strip { filter: none !important; }
  .cd__leaf { display: none !important; }
}
.cd__view--dial { width: var(--view-h); height: var(--view-h); }
.cd__face {
  position: relative;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  background: mix($subject-lilac, $stage-paper, 18%);
  box-shadow: inset 0 0 0 4px mix($subject-lilac, $stage-paper, 60%);
}
.cd__sector {
  position: absolute;
  inset: 8%;
  border-radius: 50%;
  background: conic-gradient(from 0deg, $subject-pink calc(var(--a, 0) * 1deg), transparent 0);
}
.cd__tick { position: absolute; inset: 0; }
.cd__tick::before {
  content: "";
  position: absolute;
  left: calc(50% - 2px);
  top: 2%;
  width: 4px;
  height: 8%;
  border-radius: $r-xs;
  background: mix($subject-lilac, $subject-ink, 70%);
}
.cd__tick.is-past::before { background: $subject-ink; }
.cd__needle {
  position: absolute;
  left: calc(50% - 4px);
  bottom: 50%;
  width: 8px;
  height: 40%;
  border-radius: $r-xs;
  background: $subject-ink;
  transform-origin: 50% 100%;
}
.cd__hub { position: absolute; left: calc(50% - 8px); top: calc(50% - 8px); width: 16px; height: 16px; border-radius: 50%; background: $subject-ink; }
.cd__read--center { color: $subject-ink; top: 70%; }

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);
}

.cd {
  --view-h: min(calc(100vh - 2 * clamp(8px, 4vw, 24px) - 48px), 196px);
  position: relative;
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: #17141a;
  font-size: 14px;
  line-height: 20px;
  font-weight: 600;
}

.cd__view {
  position: relative;
}

.cd__view--scene {
  width: 100%;
  height: var(--view-h);
  overflow: hidden;
  border-radius: 16px;
  background: rgb(16.6431372549%, 14.431372549%, 20.9725490196%);
}

.cd__cv {
  display: block;
  width: 100%;
  height: 100%;
}

.cd__read {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 4px;
  font-variant-numeric: tabular-nums;
}

.cd__read b {
  font-size: 28px;
  line-height: 32px;
  font-weight: 800;
}

.cd__read--center {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
}

.cd__read--corner {
  position: absolute;
  left: 8px;
  top: 8px;
}

.cd__bar {
  display: flex;
  gap: 8px;
}

.cd__btn {
  box-sizing: border-box;
  height: 36px;
  padding: 0 16px;
  border: 0;
  border-radius: 12px;
  background: rgba(23, 20, 26, 0.1);
  color: #17141a;
  font-size: 14px;
  line-height: 20px;
  font-weight: 700;
  cursor: pointer;
}

.cd__btn:focus-visible {
  outline: 2px solid #b9a0ff;
  outline-offset: 2px;
}

.cd__sr {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (prefers-reduced-motion: reduce) {
  .cd__strip {
    filter: none !important;
  }
  .cd__leaf {
    display: none !important;
  }
}
.cd__view--dial {
  width: var(--view-h);
  height: var(--view-h);
}

.cd__face {
  position: relative;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  background: rgb(95.0588235294%, 93.2941176471%, 100%);
  box-shadow: inset 0 0 0 4px #d5c6ff;
}

.cd__sector {
  position: absolute;
  inset: 8%;
  border-radius: 50%;
  background: conic-gradient(from 0deg, #ff9ebb calc(var(--a, 0) * 1deg), transparent 0);
}

.cd__tick {
  position: absolute;
  inset: 0;
}

.cd__tick::before {
  content: "";
  position: absolute;
  left: calc(50% - 2px);
  top: 2%;
  width: 4px;
  height: 8%;
  border-radius: 4px;
  background: rgb(53.4901960784%, 46.2745098039%, 73.0588235294%);
}

.cd__tick.is-past::before {
  background: #17141a;
}

.cd__needle {
  position: absolute;
  left: calc(50% - 4px);
  bottom: 50%;
  width: 8px;
  height: 40%;
  border-radius: 4px;
  background: #17141a;
  transform-origin: 50% 100%;
}

.cd__hub {
  position: absolute;
  left: calc(50% - 8px);
  top: calc(50% - 8px);
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #17141a;
}

.cd__read--center {
  color: #17141a;
  top: 70%;
}

(function () {
    const root = document.getElementById("cd");
    if (!root) return;
    function cx(s) {
        return s;
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let running = demo;
    let elapsed = 0;
    let lastTs = -1;
    let lastDraw = -1e9;
    let raf = 0;
    const hooks = { stop: () => { } };
    const offs = [];
    const TICK_COUNT = 10;
    const DEMO_SECOND_MS = 150;
    const SECOND_MS = 1000;
    const HOLD_MS = 300;
    const SPRING_K = 520;
    const DAMPING = 22;
    const SECTOR_ALPHA = 0.55;
    let secondMs = demo ? DEMO_SECOND_MS : SECOND_MS;
    let totalMs = TICK_COUNT * secondMs;
    function q(sel) {
        return root.querySelector(sel);
    }
    function on(el, type, fn) {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function clamp(v, lo, hi) {
        return Math.max(lo, Math.min(hi, v));
    }
    // 지수 접근: 프레임률이 달라도 같은 속도가 되도록 dt 를 60fps 프레임 수로 환산해 쓴다
    function approach(x, target, per, dt) {
        return x + (target - x) * (1 - Math.pow(1 - per, dt * 60));
    }
    const toggle = q('[data-r="toggle"]');
    const resetBtn = q('[data-r="reset"]');
    const status = q('[data-r="status"]');
    // 남은 시간. 경과는 rAF 타임스탬프 차이를 누적한 값이라 시계를 따로 읽지 않는다
    function remainMs() {
        return clamp(totalMs - elapsed, 0, totalMs);
    }
    function syncButtons() {
        toggle.textContent = running ? "Pause" : "Start";
        toggle.setAttribute("aria-pressed", running ? "true" : "false");
    }
    // 스크린리더 안내는 멈출 때와 끝날 때만 갱신한다. 시연 루프 중에는 읽지 않는다
    function say(msg) {
        if (!demo)
            status.textContent = msg;
    }
    function stopDemo() {
        if (!demo)
            return;
        demo = false;
        root.classList.remove("is-demo");
        root.removeAttribute("data-demo");
        hooks.stop();
    }
    function restart() {
        elapsed = 0;
        resetState();
    }
    function update(dt) {
        tick(dt);
        draw();
    }
    function frame(ts) {
        raf = requestAnimationFrame(frame);
        const raw = lastTs < 0 ? 0 : ts - lastTs;
        lastTs = ts;
        if (running) {
            elapsed += raw;
            if (demo) {
                const cycle = totalMs + HOLD_MS;
                if (elapsed >= cycle) {
                    elapsed %= cycle;
                    resetState();
                }
            }
            else if (elapsed >= totalMs) {
                elapsed = totalMs;
                running = false;
                say("Time is up");
                syncButtons();
            }
        }
        if (reduce && ts - lastDraw < 250)
            return;
        lastDraw = ts;
        update(Math.min(raw, 50) / 1000);
    }
    on(toggle, "click", () => {
        stopDemo();
        if (!running && elapsed >= totalMs)
            restart();
        running = !running;
        say(running ? "" : "Paused");
        syncButtons();
        update(0);
    });
    on(resetBtn, "click", () => {
        stopDemo();
        running = false;
        restart();
        say("");
        syncButtons();
        update(0);
    });
    const sector = q('[data-r="sector"]');
    const needle = q('[data-r="needle"]');
    const face = q('[data-r="face"]');
    const num = q('[data-r="num"]');
    const STEP_DEG = 360 / TICK_COUNT;
    const ticks = [];
    for (let i = 0; i < TICK_COUNT; i++) {
        const t = document.createElement("i");
        t.className = cx("cd__tick");
        t.style.transform = "rotate(" + i * STEP_DEG + "deg)";
        face.appendChild(t);
        ticks.push(t);
    }
    let angle = 0;
    let vel = 0;
    let passed = 0;
    // 지난 눈금 수: secondMs 가 한 번 지날 때마다 한 칸
    function passedTicks() {
        return Math.min(TICK_COUNT, Math.floor(elapsed / secondMs + 1e-6));
    }
    function resize() { }
    function resetState() {
        angle = 0;
        vel = 0;
        passed = 0;
    }
    hooks.stop = () => {
        elapsed *= SECOND_MS / secondMs;
        secondMs = SECOND_MS;
        totalMs = TICK_COUNT * secondMs;
    };
    function tick(dt) {
        passed = passedTicks();
        const target = passed * STEP_DEG;
        if (reduce) {
            angle = target;
            vel = 0;
            return;
        }
        let left = dt;
        while (left > 0) {
            const h = Math.min(left, 1 / 240);
            vel += (-SPRING_K * (angle - target) - DAMPING * vel) * h;
            angle += vel * h;
            left -= h;
        }
    }
    function draw() {
        needle.style.transform = "rotate(" + angle.toFixed(2) + "deg)";
        // 지나온 각도까지 부채꼴을 따로 깐다. 바늘이 튕기면 부채꼴 끝도 같이 튕긴다
        sector.style.setProperty("--a", clamp(angle, 0, 360).toFixed(2));
        sector.style.opacity = String(SECTOR_ALPHA);
        ticks.forEach((t, i) => t.classList.toggle(cx("is-past"), i < passed));
        num.textContent = String(Math.ceil(remainMs() / secondMs - 1e-6));
    }
    const ro = new ResizeObserver(() => {
        resize();
        draw();
    });
    ro.observe(root);
    offs.push(() => ro.disconnect());
    resize();
    resetState();
    syncButtons();
    update(0);
    raf = requestAnimationFrame(frame);
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
    };
})();

// DialSweepTickOvershoot - vanilla 판(05-cd-dial-sweep-tick-overshoot) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./DialSweepTickOvershoot.module.scss";

const cx = (s: string): string => s.split(" ").map((n) => styles[n] ?? n).join(" ");

export default function DialSweepTickOvershoot() {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const rootEl = rootRef.current;
    if (!rootEl) return;
    const root: HTMLElement = rootEl;
    const reduce: boolean = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo: boolean = !reduce;
    let running: boolean = demo;
    let elapsed = 0;
    let lastTs = -1;
    let lastDraw = -1e9;
    let raf = 0;
    const hooks: { stop: () => void } = { stop: () => {} };
    const offs: Array<() => void> = [];
    const TICK_COUNT = 10;
    const DEMO_SECOND_MS = 150;
    const SECOND_MS = 1000;
    const HOLD_MS = 300;
    const SPRING_K = 520;
    const DAMPING = 22;
    const SECTOR_ALPHA = 0.55;
    let secondMs = demo ? DEMO_SECOND_MS : SECOND_MS;
    let totalMs = TICK_COUNT * secondMs;
    function q<T extends Element>(sel: string): T {
        return root.querySelector(sel) as T;
    }
    function on(el: EventTarget, type: string, fn: (e: Event) => void): void {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function clamp(v: number, lo: number, hi: number): number {
        return Math.max(lo, Math.min(hi, v));
    }
    // 지수 접근: 프레임률이 달라도 같은 속도가 되도록 dt 를 60fps 프레임 수로 환산해 쓴다
    function approach(x: number, target: number, per: number, dt: number): number {
        return x + (target - x) * (1 - Math.pow(1 - per, dt * 60));
    }
    const toggle = q<HTMLButtonElement>('[data-r="toggle"]');
    const resetBtn = q<HTMLButtonElement>('[data-r="reset"]');
    const status = q<HTMLElement>('[data-r="status"]');
    // 남은 시간. 경과는 rAF 타임스탬프 차이를 누적한 값이라 시계를 따로 읽지 않는다
    function remainMs(): number {
        return clamp(totalMs - elapsed, 0, totalMs);
    }
    function syncButtons(): void {
        toggle.textContent = running ? "멈춤" : "시작";
        toggle.setAttribute("aria-pressed", running ? "true" : "false");
    }
    // 스크린리더 안내는 멈출 때와 끝날 때만 갱신한다. 시연 루프 중에는 읽지 않는다
    function say(msg: string): void {
        if (!demo) status.textContent = msg;
    }
    function stopDemo(): void {
        if (!demo) return;
        demo = false;
        root.classList.remove("is-demo");
        root.removeAttribute("data-demo");
        hooks.stop();
    }
    function restart(): void {
        elapsed = 0;
        resetState();
    }
    function update(dt: number): void {
        tick(dt);
        draw();
    }
    function frame(ts: number): void {
        raf = requestAnimationFrame(frame);
        const raw = lastTs < 0 ? 0 : ts - lastTs;
        lastTs = ts;
        if (running) {
            elapsed += raw;
            if (demo) {
                const cycle = totalMs + HOLD_MS;
                if (elapsed >= cycle) {
                    elapsed %= cycle;
                    resetState();
                }
            } else if (elapsed >= totalMs) {
                elapsed = totalMs;
                running = false;
                say("시간이 다 됐습니다");
                syncButtons();
            }
        }
        if (reduce && ts - lastDraw < 250) return;
        lastDraw = ts;
        update(Math.min(raw, 50) / 1000);
    }
    on(toggle, "click", () => {
        stopDemo();
        if (!running && elapsed >= totalMs) restart();
        running = !running;
        say(running ? "" : "멈췄습니다");
        syncButtons();
        update(0);
    });
    on(resetBtn, "click", () => {
        stopDemo();
        running = false;
        restart();
        say("");
        syncButtons();
        update(0);
    });
    const sector = q<HTMLElement>('[data-r="sector"]');
    const needle = q<HTMLElement>('[data-r="needle"]');
    const face = q<HTMLElement>('[data-r="face"]');
    const num = q<HTMLElement>('[data-r="num"]');
    const STEP_DEG = 360 / TICK_COUNT;
    const ticks: HTMLElement[] = [];
    for (let i = 0; i < TICK_COUNT; i++) {
        const t = document.createElement("i");
        t.className = cx("cd__tick");
        t.style.transform = "rotate(" + i * STEP_DEG + "deg)";
        face.appendChild(t);
        ticks.push(t);
    }
    let angle = 0;
    let vel = 0;
    let passed = 0;
    // 지난 눈금 수: secondMs 가 한 번 지날 때마다 한 칸
    function passedTicks(): number {
        return Math.min(TICK_COUNT, Math.floor(elapsed / secondMs + 1e-6));
    }
    function resize(): void {}
    function resetState(): void {
        angle = 0;
        vel = 0;
        passed = 0;
    }
    hooks.stop = () => {
        elapsed *= SECOND_MS / secondMs;
        secondMs = SECOND_MS;
        totalMs = TICK_COUNT * secondMs;
    };
    function tick(dt: number): void {
        passed = passedTicks();
        const target = passed * STEP_DEG;
        if (reduce) {
            angle = target;
            vel = 0;
            return;
        }
        let left = dt;
        while (left > 0) {
            const h = Math.min(left, 1 / 240);
            vel += (-SPRING_K * (angle - target) - DAMPING * vel) * h;
            angle += vel * h;
            left -= h;
        }
    }
    function draw(): void {
        needle.style.transform = "rotate(" + angle.toFixed(2) + "deg)";
        // 지나온 각도까지 부채꼴을 따로 깐다. 바늘이 튕기면 부채꼴 끝도 같이 튕긴다
        sector.style.setProperty("--a", clamp(angle, 0, 360).toFixed(2));
        sector.style.opacity = String(SECTOR_ALPHA);
        ticks.forEach((t, i) => t.classList.toggle(cx("is-past"), i < passed));
        num.textContent = String(Math.ceil(remainMs() / secondMs - 1e-6));
    }
    const ro = new ResizeObserver(() => {
        resize();
        draw();
    });
    ro.observe(root);
    offs.push(() => ro.disconnect());
    resize();
    resetState();
    syncButtons();
    update(0);
    raf = requestAnimationFrame(frame);
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
    };
  }, []);

  return (
    <div className={cx("cd") + " is-demo"} id="cd" data-demo="1" ref={rootRef}>
      <div className={cx("cd__view cd__view--dial")}>
      <div className={cx("cd__face")} data-r="face" role="img" aria-label="눈금마다 튕기는 다이얼">
      <div className={cx("cd__sector")} data-r="sector"></div>
      <div className={cx("cd__needle")} data-r="needle"></div>
      <i className={cx("cd__hub")}></i>
      </div>
      <p className={cx("cd__read cd__read--center")} role="timer"><b data-r="num">10</b><span>초</span></p>
      </div>
      <div className={cx("cd__bar")}>
        <button className={cx("cd__btn")} type="button" data-r="toggle">멈춤</button>
        <button className={cx("cd__btn")} type="button" data-r="reset">다시</button>
      </div>
      <p className={cx("cd__sr")} aria-live="polite" data-r="status"></p>
    </div>
  );
}