/* ===== ベーススタイル ===== */
body {
  background: #fff9f4;
  font-family: "Hiragino Maru Gothic ProN", "Yu Gothic", sans-serif;
  margin: 0;
  padding: 0;
  color: #444;
  line-height: 1.9;
}

.book-cover, .book-page {
  max-width: 600px;
  margin: 30px auto;
  padding: 30px;
  background: #ffffff;
  border-radius: 20px;
  border: 5px solid #ffd9e6;
  box-shadow: 0 6px 16px rgba(0,0,0,0.1);
  text-align: center;
}

.book-img, .page-img {
  width: 100%;
  max-width: 300px;
  margin: 20px 0;
  border-radius: 16px;
}

.btn-start {
  display: inline-block;
  margin-top: 20px;
  background: #ff88aa;
  color: white;
  padding: 12px 24px;
  font-size: 18px;
  border-radius: 12px;
  text-decoration: none;
  transition: 0.3s;
}

.btn-start:hover {
  background: #ff6699;
}

.page-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 30px;
}

.page-nav a {
  color: #ff6699;
  font-weight: bold;
  text-decoration: none;
}

/* ===== スマホ対応 ===== */
@media screen and (max-width: 600px) {
  .book-cover, .book-page {
    max-width: 90%;      /* 画面幅に合わせる */
    padding: 20px;
    border-width: 3px;
    margin: 20px auto;
  }
  .book-img, .page-img {
    max-width: 80%;      /* 画面幅に合わせて縮小 */
    margin: 15px 0;
  }
  .btn-start {
    padding: 10px 20px;
    font-size: 16px;
  }
  .page-nav {
    flex-direction: column;
    gap: 10px;
  }
}