04クリック地点から円形に広がる

<main class="stage">
  <div class="pages is-demo">
    <section class="page page--a">
      <p class="page__tag">SETTINGS</p>
      <h2 class="page__title">ライトモード</h2>
      <p class="page__body">明るい画面</p>
    </section>
    <section class="page page--b page--circle">
      <p class="page__tag">SETTINGS</p>
      <h2 class="page__title">ダークモード</h2>
      <p class="page__body">目に優しい画面</p>
    </section>
  </div>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 (값은 토큰에서 받는다) ──────
$duration: $dur-enter;
$easing: $ease-pop;
$color: $subject-blue;

// ── 데모 무대 ───────────────────────────────
@include stage($stage-paper);

.pages { position: relative; width: min(300px, 88%); height: 150px; border-radius: $r-card; overflow: hidden; box-shadow: $shadow-raised; }
.page {
  position: absolute; inset: 0; box-sizing: border-box;
  display: flex; flex-direction: column; justify-content: center; gap: 6px;
  padding: clamp(12px, 5vw, 20px); text-align: left;
}
.page--a { background: #fff; color: $subject-ink; }
.page--b { background: $subject-ink; color: #fff; }
.page__tag { margin: 0; font-weight: 700; font-size: clamp(9px, 2.6vw, 11px); line-height: 1; font-family: inherit; letter-spacing: .12em; opacity: .6; }
.page__title { margin: 0; font-weight: 700; font-size: clamp(14px, 4.2vw, 18px); line-height: 1.3; font-family: inherit; }
.page__body { margin: 0; font-weight: 400; font-size: clamp(11px, 3.2vw, 13px); line-height: 1.5; font-family: inherit; opacity: .82; }

// 클릭 지점(여기서는 우측 상단 토글 자리)에서 원이 자라며 다음 페이지를 덮는다.
// clip-path 는 레이아웃을 다시 계산하지 않아 transform 과 같은 값으로 취급한다.
.page--circle {
  clip-path: circle(0% at 88% 14%);
  animation: circle-grow $dur-loop $easing infinite;
}

@keyframes circle-grow {
  0%, 5% { clip-path: circle(0% at 88% 14%); }
  50% { clip-path: circle(150% at 88% 14%); }
  95%, 100% { clip-path: circle(0% at 88% 14%); }
}

// ── 접근성: 움직임 줄이기 설정이면 최종 상태만 고정으로 ────────
@media (prefers-reduced-motion: reduce) {
  .page--circle { animation: none !important; clip-path: circle(0% at 88% 14%); }
}

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);
}

.pages {
  position: relative;
  width: min(300px, 88%);
  height: 150px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.page {
  position: absolute;
  inset: 0;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 6px;
  padding: clamp(12px, 5vw, 20px);
  text-align: left;
}

.page--a {
  background: #fff;
  color: #17141a;
}

.page--b {
  background: #17141a;
  color: #fff;
}

.page__tag {
  margin: 0;
  font-weight: 700;
  font-size: clamp(9px, 2.6vw, 11px);
  line-height: 1;
  font-family: inherit;
  letter-spacing: 0.12em;
  opacity: 0.6;
}

.page__title {
  margin: 0;
  font-weight: 700;
  font-size: clamp(14px, 4.2vw, 18px);
  line-height: 1.3;
  font-family: inherit;
}

.page__body {
  margin: 0;
  font-weight: 400;
  font-size: clamp(11px, 3.2vw, 13px);
  line-height: 1.5;
  font-family: inherit;
  opacity: 0.82;
}

.page--circle {
  clip-path: circle(0% at 88% 14%);
  animation: circle-grow 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

@keyframes circle-grow {
  0%, 5% {
    clip-path: circle(0% at 88% 14%);
  }
  50% {
    clip-path: circle(150% at 88% 14%);
  }
  95%, 100% {
    clip-path: circle(0% at 88% 14%);
  }
}
@media (prefers-reduced-motion: reduce) {
  .page--circle {
    animation: none !important;
    clip-path: circle(0% at 88% 14%);
  }
}

import type { CSSProperties, ReactNode, MouseEvent } from "react";
import { useState } from "react";
import styles from "./CircleRevealTransition.module.scss";

export type CircleRevealTransitionProps = {
  active: "a" | "b";
  pageA: ReactNode;
  pageB: ReactNode;
  /** 원이 다 퍼지는 시간 (기본 600ms) */
  duration?: number;
  easing?: string;
  className?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--x"?: string; "--y"?: string };

export default function CircleRevealTransition({
  active,
  pageA,
  pageB,
  duration = 600,
  easing = "cubic-bezier(.2,1.4,.4,1)",
  className = "",
}: CircleRevealTransitionProps) {
  const [origin, setOrigin] = useState({ x: "88%", y: "14%" });

  const remember = (e: MouseEvent<HTMLDivElement>) => {
    const r = e.currentTarget.getBoundingClientRect();
    setOrigin({ x: `${((e.clientX - r.left) / r.width) * 100}%`, y: `${((e.clientY - r.top) / r.height) * 100}%` });
  };

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--x": origin.x, "--y": origin.y };
  return (
    <div className={`${styles.pages} ${className}`} style={vars} data-active={active} onClickCapture={remember}>
      <section className={styles.pageA}>{pageA}</section>
      <section className={styles.pageB}>{pageB}</section>
    </div>
  );
}