* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  font-family: Arial, "Hiragino Kaku Gothic ProN", "Yu Gothic", Meiryo, sans-serif;
  background: #f5f6f8;
  color: #222;
  line-height: 1.6;
}

/* =========================
   PC：左固定目次
   ========================= */
.toc-card {
  position: fixed;
  top: 24px;
  left: 24px;
  width: 220px;
  z-index: 1000;
}

.toc-card__inner {
  background: #ffffff;
  border: 1px solid #d9dee5;
  border-radius: 16px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
  padding: 16px;
}

.toc-card__title {
  margin: 0 0 12px;
  font-size: 18px;
  font-weight: 700;
}

.toc-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.toc-button {
  width: 100%;
  border: 1px solid #cfd6df;
  background: #ffffff;
  color: #222;
  border-radius: 10px;
  padding: 12px 14px;
  font-size: 14px;
  text-align: left;
  cursor: pointer;
  transition: background-color 0.2s, border-color 0.2s, color 0.2s, transform 0.2s;
}

.toc-button:hover {
  background: #f0f6ff;
  border-color: #8bb8ff;
}

.toc-button.is-active {
  background: #0078d4;
  border-color: #0078d4;
  color: #ffffff;
}

/* =========================
   メインコンテンツ
   ========================= */
.content {
  margin-left: 280px;
  padding: 32px 24px;
}

.viewer-section {
  max-width: 760px;
  margin: 0 auto;
}

.viewer-header {
  margin-bottom: 20px;
}

.viewer-header h1 {
  margin: 0 0 8px;
  font-size: 28px;
  line-height: 1.3;
}

.viewer-header p {
  margin: 0;
  font-size: 14px;
  color: #666;
}

.manga-viewer {
  background: #ffffff;
  border: 1px solid #d9dee5;
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.06);
  padding: 16px;
}

.manga-viewer img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 12px;
  opacity: 1;
  transition: opacity 0.18s ease;
}

.manga-viewer img.is-changing {
  opacity: 0.25;
}

/* =========================
   スマホ：下固定目次
   ========================= */
@media (max-width: 768px) {
  .toc-card {
    top: auto;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    padding: 0;
  }

  .toc-card__inner {
    border-radius: 18px 18px 0 0;
    padding: 12px 12px calc(12px + env(safe-area-inset-bottom));
    box-shadow: 0 -8px 24px rgba(0, 0, 0, 0.12);
  }

  .toc-card__title {
    font-size: 16px;
    margin-bottom: 10px;
  }

  .toc-list {
    flex-direction: row;
    gap: 8px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    padding-bottom: 2px;
  }

  .toc-list::-webkit-scrollbar {
    height: 6px;
  }

  .toc-list::-webkit-scrollbar-thumb {
    background: #c7cfdb;
    border-radius: 999px;
  }

  .toc-button {
    flex: 0 0 auto;
    min-width: 120px;
    text-align: center;
    white-space: nowrap;
    padding: 12px 14px;
  }

  .content {
    margin-left: 0;
    padding: 20px 16px 160px;
  }

  .viewer-header h1 {
    font-size: 24px;
  }

  .manga-viewer {
    padding: 12px;
    border-radius: 16px;
  }
}
``