02밝은 값과 어두운 값이 반대로 겹쳐 도드라지는 글자

<main class="stage">
<div class="em is-demo" id="em">
  <p class="em__badge"><span class="em__badgeLabel">빛 각도</span> <span class="em__badgeValue" id="emValue">0deg</span></p>
  <h1 class="em__word" id="emWord">요철</h1>
</div>
</main>

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

// 핵심: 각도 값(angleDeg) 하나로 밝은 그림자와 어두운 그림자를 서로 반대 방향에 배치한다.
// 각도가 돌면 빛이 도는 것처럼 도드라짐과 파임이 자리를 바꾼다.

$duration: $dur-loop;
$easing: linear;
$color: $subject-ink;

@include stage($stage-yellow);

.em {
  display: grid;
  gap: $sp-4;
  justify-items: center;
  text-align: center;
}

.em__badge {
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .08);
  color: $subject-ink;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.em__word {
  margin: 0;
  font-weight: 800;
  font-size: clamp(72px, 24vw, 140px);
  line-height: 1;
  white-space: nowrap;
  color: $color;
  will-change: text-shadow;
}

@media (max-width: 340px) {
  .em__word { font-size: clamp(52px, 26vw, 92px); }
}

@media (prefers-reduced-motion: reduce) {
  .em__word { transition: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.em {
  display: grid;
  gap: 16px;
  justify-items: center;
  text-align: center;
}

.em__badge {
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.08);
  color: #17141a;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.em__word {
  margin: 0;
  font-weight: 800;
  font-size: clamp(72px, 24vw, 140px);
  line-height: 1;
  white-space: nowrap;
  color: #17141a;
  will-change: text-shadow;
}

@media (max-width: 340px) {
  .em__word {
    font-size: clamp(52px, 26vw, 92px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .em__word {
    transition: none;
  }
}

(function () {
  var EMBOSS_DEPTH_PX = 12.5;
  var PERIOD_MS = 1000;

  var word = document.getElementById('emWord');
  var value = document.getElementById('emValue');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  // 값(angleDeg) 하나로 밝은 그림자·어두운 그림자를 서로 반대 방향에 배치한다
  function buildEmbossShadow(angleDeg) {
    var rad = (angleDeg * Math.PI) / 180;
    var lx = (Math.cos(rad) * EMBOSS_DEPTH_PX).toFixed(2);
    var ly = (Math.sin(rad) * EMBOSS_DEPTH_PX).toFixed(2);
    var dx = (-Math.cos(rad) * EMBOSS_DEPTH_PX).toFixed(2);
    var dy = (-Math.sin(rad) * EMBOSS_DEPTH_PX).toFixed(2);
    return [
      lx + 'px ' + ly + 'px 0 rgba(255,255,255,.85)',
      dx + 'px ' + dy + 'px 1px rgba(10,10,14,.75)'
    ].join(', ');
  }

  function renderEmboss(angleDeg) {
    word.style.textShadow = buildEmbossShadow(angleDeg);
    value.textContent = Math.round(angleDeg % 360) + 'deg';
  }

  var startTime = null;
  function loop(now) {
    if (startTime === null) startTime = now;
    var t = (now - startTime) % PERIOD_MS;
    var angle = (t / PERIOD_MS) * 360;
    renderEmboss(angle);
    requestAnimationFrame(loop);
  }

  if (reduce) {
    renderEmboss(45);
  } else {
    requestAnimationFrame(loop);
  }
})();

// TextShadowEmbossEngraveDual — vanilla 판(run/412/demo/02-text-shadow-emboss-engrave-dual/index.html) 의 React 포트.
// 각도 값(angleDeg) 하나로 밝은 그림자와 어두운 그림자를 서로 반대 방향에 배치한다.
// 각도가 돌면 빛이 도는 것처럼 도드라짐과 파임이 자리를 바꾼다.
import { useEffect, useRef, useState } from "react";
import styles from "./TextShadowEmbossEngraveDual.module.scss";

type Box<T> = { current: T };

const EMBOSS_DEPTH_PX = 12.5;
const PERIOD_MS = 1000;

function buildEmbossShadow(angleDeg: number): string {
  const rad = (angleDeg * Math.PI) / 180;
  const lx = (Math.cos(rad) * EMBOSS_DEPTH_PX).toFixed(2);
  const ly = (Math.sin(rad) * EMBOSS_DEPTH_PX).toFixed(2);
  const dx = (-Math.cos(rad) * EMBOSS_DEPTH_PX).toFixed(2);
  const dy = (-Math.sin(rad) * EMBOSS_DEPTH_PX).toFixed(2);
  return [
    lx + "px " + ly + "px 0 rgba(255,255,255,.85)",
    dx + "px " + dy + "px 1px rgba(10,10,14,.75)"
  ].join(", ");
}

export default function TextShadowEmbossEngraveDual() {
  const wordRef = useRef<HTMLHeadingElement | null>(null);
  const valueRef = useRef<HTMLSpanElement | null>(null);
  const t0Ref = useRef<number>(0) as Box<number>;
  const frameRef = useRef<number>(0) as Box<number>;
  const [demo] = useState(true);
  const [reduce, setReduce] = useState(false);

  function render(angleDeg: number): void {
    const word = wordRef.current;
    const value = valueRef.current;
    if (!word || !value) return;
    word.style.textShadow = buildEmbossShadow(angleDeg);
    value.textContent = Math.round(angleDeg % 360) + "deg";
  }

  useEffect(() => {
    setReduce(window.matchMedia("(prefers-reduced-motion: reduce)").matches);
  }, []);

  useEffect(() => {
    if (reduce) {
      render(45);
      return;
    }
    function loop(now: number): void {
      if (t0Ref.current === 0) t0Ref.current = now;
      const t = (now - t0Ref.current) % PERIOD_MS;
      const angle = (t / PERIOD_MS) * 360;
      render(angle);
      frameRef.current = requestAnimationFrame(loop);
    }
    frameRef.current = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(frameRef.current);
  }, [reduce]);

  const cls = [styles.em, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls}>
        <p className={styles.badge}><span>빛 각도</span> <span ref={valueRef}>0deg</span></p>
        <h1 className={styles.word} ref={wordRef}>요철</h1>
      </div>
    </main>
  );
}