04Hiệu ứng mở sách

<main class="stage">
  <div class="book">
    <div class="book__page">Chương 1. Bắt đầu</div>
    <div class="book__cover is-demo">
      <div class="book__face book__face--front">Sổ tay</div>
      <div class="book__face book__face--back"></div>
    </div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────
$duration: $dur-enter;                                  // 표지가 열리는 시간
$easing: $ease-spring;
$color: $subject-blue-deep;                             // 표지 색 (크림 글자가 얹히므로 진한 파랑)

@include stage($stage-paper);

.book {
  position: relative;
  width: 170px;
  height: 130px;
  perspective: 800px;
}
.book__page {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  font-weight: 700;
  font-size: 13px;
  line-height: 1.3;
  font-family: inherit;
  box-shadow: $shadow-press;
}

// 표지는 왼쪽 모서리를 축으로 돈다 — 카드 전체를 뒤집는 006 의 flip 과 달리 한쪽 변만 경첩이다
.book__cover {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  transform-origin: left center; // 규칙8: 왼쪽 변 경첩
  animation: open $dur-loop $easing infinite;
}
.book__face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: $r-card;
  font-weight: 700;
  font-size: 15px;
  line-height: 1;
  font-family: inherit;
  color: $subject-cream;
  backface-visibility: hidden;                            // 표지 안쪽 면이 앞면 글자와 겹쳐 비치지 않게
}
.book__face--front { background: $color; }
.book__face--back  { background: darken($color, 14%); transform: rotateY(180deg); }

@keyframes open {
  0%, 15%  { transform: rotateY(0deg); }
  55%      { transform: rotateY(-150deg); }
  85%, 100% { transform: rotateY(0deg); }
}

// ── 접근성: 움직임 줄이기 설정이면 펼친 상태로 고정 ────────────
@media (prefers-reduced-motion: reduce) {
  .book__cover { animation: none; transform: rotateY(-150deg); }
}

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);
}

.book {
  position: relative;
  width: 170px;
  height: 130px;
  perspective: 800px;
}

.book__page {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  font-weight: 700;
  font-size: 13px;
  line-height: 1.3;
  font-family: inherit;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}

.book__cover {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  transform-origin: left center;
  animation: open 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.book__face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: 16px;
  font-weight: 700;
  font-size: 15px;
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  backface-visibility: hidden;
}

.book__face--front {
  background: #0a4fe8;
}

.book__face--back {
  background: rgb(2.7645438341%, 21.8398962891%, 64.1374169503%);
  transform: rotateY(180deg);
}

@keyframes open {
  0%, 15% {
    transform: rotateY(0deg);
  }
  55% {
    transform: rotateY(-150deg);
  }
  85%, 100% {
    transform: rotateY(0deg);
  }
}
@media (prefers-reduced-motion: reduce) {
  .book__cover {
    animation: none;
    transform: rotateY(-150deg);
  }
}

import type { CSSProperties } from "react";
import styles from "./BookOpen.module.scss";

export type BookOpenProps = {
  duration?: number;
  easing?: string;
  /** 표지 색 */
  color?: string;
  cover?: string;
  page?: string;
};

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

export default function BookOpen({
  duration = 600,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#0a4fe8",
  cover = "매뉴얼",
  page = "1장. 시작하기",
}: BookOpenProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <div className={styles.book} style={vars}>
      <div className={styles.page}>{page}</div>
      <div className={styles.cover}>
        <div className={`${styles.face} ${styles.front}`}>{cover}</div>
        <div className={`${styles.face} ${styles.back}`} />
      </div>
    </div>
  );
}