01Case hero — a top section that recomputes its headline metric every frame to count it up

<main class="stage">
<section class="hero" id="hero">
  <p class="eyebrow" id="eyebrow">Project Nova · Case Study</p>
  <p class="metricLabel" id="metricLabel">Key metric</p>
  <p class="metricRow">
    <span class="metricNum" id="metricNum">0</span><span class="metricUnit" id="metricUnit">%</span>
  </p>
  <p class="hint" id="hint">While you stay on screen, the key metric is recalculated from 0 every frame and counted up.</p>
</section>
</main>

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

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

@include stage($stage-ink);

.hero {
  position: relative;
  width: 100%;
  max-width: 420px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  text-align: center;
}

.eyebrow {
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba($subject-cream, .12);
  color: $subject-cream;
  font-weight: 500;
  font-size: 10px;
  letter-spacing: .04em;
}

.metricLabel {
  margin: 0;
  color: rgba($subject-cream, .72);
  font-weight: 500;
  font-size: 12px;
}

.metricRow {
  position: relative;
  margin: 0;
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: $sp-1;
  padding: $sp-2 $sp-6;
}

.metricRow::before {
  content: "";
  position: absolute;
  inset: 0;
  margin: auto;
  width: 120px;
  height: 120px;
  border-radius: $r-pill;
  background: radial-gradient(circle, rgba($color, .38), rgba($color, 0) 70%);
  animation: halo $duration $easing infinite;
  z-index: 0;
}

.metricNum {
  --num-w: 88px;
  position: relative;
  z-index: 1;
  display: inline-block;
  min-width: var(--num-w);
  text-align: right;
  font-weight: 700;
  font-size: 44px;
  font-variant-numeric: tabular-nums;
  color: $subject-cream;
}

.metricUnit {
  position: relative;
  z-index: 1;
  font-weight: 700;
  font-size: 22px;
  color: $color;
}

.hint {
  margin: 0;
  padding: 0 $sp-2;
  color: rgba($subject-cream, .72);
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
}

@keyframes halo {
  0%, 100% { transform: scale(.86); opacity: .5; }
  50% { transform: scale(1.12); opacity: 1; }
}

@media (max-width: 340px) {
  .hero { max-width: 300px; gap: $sp-1; }
  .metricNum { font-size: 32px; }
  .metricUnit { font-size: 16px; }
  .hint { font-size: 9px; }
  .metricRow { padding: $sp-1 $sp-4; }
}

@media (prefers-reduced-motion: reduce) {
  .metricRow::before {
    animation: none;
    opacity: .7;
  }
}

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);
}

.hero {
  position: relative;
  width: 100%;
  max-width: 420px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  text-align: center;
}

.eyebrow {
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.12);
  color: #fff7e6;
  font-weight: 500;
  font-size: 10px;
  letter-spacing: 0.04em;
}

.metricLabel {
  margin: 0;
  color: rgba(255, 247, 230, 0.72);
  font-weight: 500;
  font-size: 12px;
}

.metricRow {
  position: relative;
  margin: 0;
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 4px;
  padding: 8px 24px;
}

.metricRow::before {
  content: "";
  position: absolute;
  inset: 0;
  margin: auto;
  width: 120px;
  height: 120px;
  border-radius: 999px;
  background: radial-gradient(circle, rgba(10, 79, 232, 0.38), rgba(10, 79, 232, 0) 70%);
  animation: halo 2s ease-out infinite;
  z-index: 0;
}

.metricNum {
  --num-w: 88px;
  position: relative;
  z-index: 1;
  display: inline-block;
  min-width: var(--num-w);
  text-align: right;
  font-weight: 700;
  font-size: 44px;
  font-variant-numeric: tabular-nums;
  color: #fff7e6;
}

.metricUnit {
  position: relative;
  z-index: 1;
  font-weight: 700;
  font-size: 22px;
  color: #0a4fe8;
}

.hint {
  margin: 0;
  padding: 0 8px;
  color: rgba(255, 247, 230, 0.72);
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
}

@keyframes halo {
  0%, 100% {
    transform: scale(0.86);
    opacity: 0.5;
  }
  50% {
    transform: scale(1.12);
    opacity: 1;
  }
}
@media (max-width: 340px) {
  .hero {
    max-width: 300px;
    gap: 4px;
  }
  .metricNum {
    font-size: 32px;
  }
  .metricUnit {
    font-size: 16px;
  }
  .hint {
    font-size: 9px;
  }
  .metricRow {
    padding: 4px 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .metricRow::before {
    animation: none;
    opacity: 0.7;
  }
}

// 사례 히어로(01) — 값을 누적하지 않고, 매 애니메이션 프레임마다 경과 비율(t)로부터
// 목표값까지의 값을 공식(eased(t) * target)으로 처음부터 다시 구해 카운트업한다(계산 한 겹).
// 자릿수가 늘어나는 순간에는 canvas measureText 로 그 시점 문자열의 실제 렌더 폭을 다시 재
// 숫자 칸의 폭(--num-w)을 갱신해, 다음 문자가 밀리지 않고 자리에 맞춰 넓어지게 한다.
(function () {
  var numEl = document.getElementById('metricNum');
  var wrapEl = numEl ? numEl.parentElement : null;
  if (!numEl || !wrapEl) return;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var TARGET = 128;
  var EASE_POW = 2;      // 변형: 2 → 4
  var ANIM_MS = 1300;
  var CYCLE_MS = 1900;

  var measureCv = document.createElement('canvas');
  var measureCtx = measureCv.getContext('2d');

  function measureWidth(text, px) {
    if (!measureCtx) return text.length * px * 0.62;
    measureCtx.font = '700 ' + px + 'px -apple-system, "Segoe UI", sans-serif';
    return measureCtx.measureText(text).width;
  }

  var lastDigits = -1;

  function applyValue(v) {
    numEl.textContent = String(v);
    var digits = String(v).length;
    if (digits !== lastDigits) {
      lastDigits = digits;
      var px = parseFloat(getComputedStyle(numEl).fontSize) || 44;
      var w = measureWidth(String(v), px);
      wrapEl.style.setProperty('--num-w', Math.ceil(w) + 'px');
    }
  }

  function runCycle() {
    if (reduce) { applyValue(TARGET); return; }
    var start = null;
    function frame(ts) {
      if (start === null) start = ts;
      var t = Math.min((ts - start) / ANIM_MS, 1);
      var eased = 1 - Math.pow(1 - t, EASE_POW);
      var val = Math.round(TARGET * eased);
      applyValue(val);
      if (t < 1) requestAnimationFrame(frame);
    }
    applyValue(0);
    requestAnimationFrame(frame);
  }

  runCycle();
  if (!reduce) setInterval(runCycle, CYCLE_MS);
})();

// CaseHero — vanilla 판(run/340/demo/01-case-hero/index.html) 의 React 포트.
// 값을 누적하지 않고 매 프레임 경과 비율(t)로부터 목표값까지의 값을 공식으로 처음부터 다시 구해
// 카운트업하고, 자릿수가 늘어나는 순간엔 canvas measureText 로 실제 렌더 폭을 다시 재 숫자 칸 폭을 갱신한다.
import { useEffect, useRef } from "react";
import styles from "./CaseHero.module.scss";

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

const EYEBROW = "프로젝트 노바 · 사례 연구";
const METRIC_LABEL = "핵심 성과";
const HINT = "화면에 머무는 동안 핵심 성과 수치를 0부터 매 프레임 다시 구해 카운트업합니다";

const TARGET = 128;
const EASE_POW = 2;
const ANIM_MS = 1300;
const CYCLE_MS = 1900;

export default function CaseHero({
  duration = "2s",
  easing = "ease-out",
  color = "#0a4fe8"
}: CaseHeroProps) {
  const numRef = useRef<HTMLSpanElement | null>(null);
  const wrapRef = useRef<HTMLParagraphElement | null>(null);

  useEffect(() => {
    const numEl = numRef.current;
    const wrapEl = wrapRef.current;
    if (!numEl || !wrapEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const measureCv = document.createElement("canvas");
    const measureCtx = measureCv.getContext("2d");

    function measureWidth(text: string, px: number): number {
      if (!measureCtx) return text.length * px * 0.62;
      measureCtx.font = "700 " + px + 'px -apple-system, "Segoe UI", sans-serif';
      return measureCtx.measureText(text).width;
    }

    let lastDigits = -1;

    function applyValue(v: number): void {
      numEl!.textContent = String(v);
      const digits = String(v).length;
      if (digits !== lastDigits) {
        lastDigits = digits;
        const px = parseFloat(getComputedStyle(numEl!).fontSize) || 44;
        const w = measureWidth(String(v), px);
        wrapEl!.style.setProperty("--num-w", Math.ceil(w) + "px");
      }
    }

    function runCycle(): void {
      if (reduce) { applyValue(TARGET); return; }
      let start: number | null = null;
      function frame(ts: number): void {
        if (start === null) start = ts;
        const t = Math.min((ts - start) / ANIM_MS, 1);
        const eased = 1 - Math.pow(1 - t, EASE_POW);
        const val = Math.round(TARGET * eased);
        applyValue(val);
        if (t < 1) requestAnimationFrame(frame);
      }
      applyValue(0);
      requestAnimationFrame(frame);
    }

    runCycle();
    let timer = 0;
    if (!reduce) timer = window.setInterval(runCycle, CYCLE_MS);

    return () => {
      if (timer) window.clearInterval(timer);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <section className={styles.hero}>
        <p className={styles.eyebrow}>{EYEBROW}</p>
        <p className={styles.metricLabel}>{METRIC_LABEL}</p>
        <p className={styles.metricRow} ref={wrapRef}>
          <span className={styles.metricNum} ref={numRef}>0</span>
          <span className={styles.metricUnit}>%</span>
        </p>
        <p className={styles.hint}>{HINT}</p>
      </section>
    </main>
  );
}