* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
  }

  body {
      background: #faf9f6;
      color: #1a1a1a;
      font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
          Roboto, sans-serif;
      line-height: 1.5;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 2rem 1.2rem;
  }

  .container {
      max-width: 820px;
      width: 100%;
  }

  /* ----- navigation & language ----- */
  .top-bar {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 3rem;
      padding-bottom: 0.8rem;
      border-bottom: 1px solid #e2e2e2;
      font-size: 0.9rem;
  }

  .back-home a {
      color: #6b6b6b;
      text-decoration: none;
      display: inline-flex;
      align-items: center;
      gap: 0.3rem;
  }

  .back-home a:hover {
      color: #1a1a1a;
  }

  .lang-switch a {
      color: #6b6b6b;
      text-decoration: none;
      margin-left: 1rem;
  }

  .lang-switch a.active {
      color: #1a1a1a;
      font-weight: 500;
      border-bottom: 1px solid #1a1a1a;
  }

  /* ----- hero / cover area ----- */
  .hero {
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      margin-bottom: 2.5rem;
  }

  .book-title {
      font-size: 2.8rem;
      font-weight: 470;
      letter-spacing: -0.02em;
      line-height: 1.1;
      margin-bottom: 0.25rem;
  }

  .book-subtitle {
      font-size: 1.2rem;
      font-weight: 350;
      color: #5a5a5a;
      font-style: italic;
      margin-bottom: 0.5rem;
  }

  .author-name {
      font-size: 1rem;
      color: #6b6b6b;
      margin-bottom: 2rem;
  }

  .cover-block-id {
      width: 220px;
      height: 280px;
      background: #eaeae5;
      border: 1px solid #d4d4d4;
      border-radius: 16px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: #6b6b6b;
      font-style: italic;
      font-size: 0.9rem;
      box-shadow: 0 8px 20px rgba(0, 0, 0, 0.03);
      margin-bottom: 2rem;
      background-image: url("https://cahyanudien.github.io/hening-yang-berjalan/assets/cover-id.jpg");
      background-size: cover;
      background-position: center;
  }

  .cover-block-en {
      width: 220px;
      height: 280px;
      background: #eaeae5;
      border: 1px solid #d4d4d4;
      border-radius: 16px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: #6b6b6b;
      font-style: italic;
      font-size: 0.9rem;
      box-shadow: 0 8px 20px rgba(0, 0, 0, 0.03);
      margin-bottom: 2rem;
      background-image: url("https://cahyanudien.github.io/hening-yang-berjalan/assets/cover-en.jpg");
      background-size: cover;
      background-position: center;
  }

  .pull-quote {
      font-size: 1.4rem;
      font-style: italic;
      color: #2c2c2c;
      max-width: 580px;
      margin: 1.8rem auto;
      border-left: 4px solid #c9c9c9;
      padding-left: 1.8rem;
      text-align: left;
      font-weight: 350;
  }

  /* ----- info cards (minimal stats) ----- */
  .info-grid {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 1rem;
      margin: 2.5rem 0 3rem 0;
  }

  .info-card {
      background: #ffffff;
      border: 1px solid #e2e2e2;
      border-radius: 24px;
      padding: 1rem 0.5rem;
      text-align: center;
      box-shadow: 0 2px 6px rgba(0, 0, 0, 0.01);
  }

  .info-label {
      font-size: 0.65rem;
      text-transform: uppercase;
      letter-spacing: 0.03em;
      color: #8a8a8a;
      margin-bottom: 0.3rem;
  }

  .info-value {
      font-size: 0.95rem;
      font-weight: 450;
      color: #1a1a1a;
  }

  /* ----- youtube embed (responsive) ----- */
  .video-wrapper {
      margin: 2.5rem 0;
      position: relative;
      padding-bottom: 56.25%;
      height: 0;
      background: #111;
      border-radius: 20px;
      overflow: hidden;
  }

  .video-wrapper iframe {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      border: 0;
  }

  /* ----- purchase cards (kindle, apple books, github) ----- */
  .section-title {
      font-size: 1.2rem;
      font-weight: 480;
      margin: 2.5rem 0 1.2rem 0;
      letter-spacing: -0.01em;
  }

  .purchase-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 1.2rem;
      margin: 1.5rem 0;
  }

  .purchase-card {
      background: #ffffff;
      border: 1px solid #e2e2e2;
      border-radius: 24px;
      padding: 1.5rem 1rem;
      text-decoration: none;
      color: inherit;
      display: flex;
      flex-direction: column;
      align-items: center;
      text-align: center;
      transition: all 0.2s;
  }

  .purchase-card:hover {
      border-color: #a0a0a0;
      transform: translateY(-3px);
      box-shadow: 0 12px 24px -12px rgba(0, 0, 0, 0.15);
  }

  .purchase-card.disabled-card {
      background: #f5f5f5 !important;
      color: #999 !important;
  }

  .purchase-card.disabled-card:hover {
      border-color: red !important;
      background: #ffeeee !important;
      transform: none !important;
      box-shadow: none !important;
  }

  .unavailable-badge {
      display: none;
      background: #ff4444;
      color: white;
      font-size: 0.7rem;
      font-weight: 600;
      padding: 0.25rem 0.75rem;
      border-radius: 20px;
      margin-top: 0.5rem;
      text-transform: uppercase;
      letter-spacing: 0.5px;
  }

  .purchase-card.disabled-card:hover .unavailable-badge {
      display: inline-block;
  }

  .purchase-icon {
      font-size: 2rem;
      margin-bottom: 0.8rem;
      opacity: 0.8;
  }

  .purchase-title {
      font-weight: 600;
      font-size: 1rem;
      margin-bottom: 0.3rem;
  }

  .purchase-sub {
      font-size: 0.75rem;
      color: #6b6b6b;
  }

  /* ----- cards (intro, outro) ----- */
  .intro-card,
  .outro-card {
      background: #ffffff;
      border: 1px solid #e2e2e2;
      border-radius: 28px;
      padding: 2rem 2.2rem;
      margin: 2.5rem 0;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.02);
  }

  .intro-card p,
  .outro-card p {
      font-size: 1.05rem;
      color: #2c2c2c;
      margin-bottom: 1rem;
      font-style: italic;
  }

  .intro-card .attribution,
  .outro-card .attribution {
      font-size: 0.85rem;
      color: #8a8a8a;
      font-style: normal;
      margin-top: 0.8rem;
  }

  /* ----- TOC with mobile scroll fix (shows all content) ----- */
  .toc-full {
      background: #ffffff;
      border: 1px solid #e2e2e2;
      border-radius: 28px;
      padding: 2rem;
      margin: 2rem 0;
  }

  .toc-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 2rem;
      margin-top: 1.8rem;
  }

  .toc-part h3 {
      font-size: 1.1rem;
      font-weight: 500;
      margin-bottom: 1.2rem;
      color: #1a1a1a;
      border-bottom: 1px solid #eee;
      padding-bottom: 0.5rem;
  }

  .toc-part ul {
      list-style: none;
  }

  .toc-part li {
      font-size: 0.9rem;
      color: #4a4a4a;
      margin-bottom: 0.7rem;
      padding-left: 0.5rem;
      border-left: 1px solid transparent;
      transition: border 0.1s;
  }

  .toc-part li:hover {
      border-left-color: #a0a0a0;
  }

  /* mobile fix */
  @media (max-width: 600px) {
      .toc-grid {
          grid-template-columns: 1fr;
          gap: 1.5rem;
      }

      .purchase-grid {
          grid-template-columns: 1fr;
      }

      .info-grid {
          grid-template-columns: repeat(2, 1fr);
      }
  }

  /* author snippet */
  .author-snippet {
      display: flex;
      gap: 1.2rem;
      align-items: center;
      background: #f8f8f8;
      border-radius: 40px;
      padding: 0.8rem 1.5rem;
      margin: 1.5rem 0;
  }

  .author-avatar {
      width: 48px;
      height: 48px;
      background: #e0e0e0;
      border-radius: 50%;
      background-image: url("https://avatars.githubusercontent.com/cahyanudien");
      background-size: cover;
      background-position: center;
      border: 1px solid #ddd;
      flex-shrink: 0;
  }

  /* ----- action buttons ----- */
  .action-row {
      display: flex;
      flex-wrap: wrap;
      gap: 1rem;
      justify-content: center;
      margin: 2rem 0;
  }

  .btn-primary {
      background: #1a1a1a;
      color: white;
      padding: 0.8rem 2.2rem;
      border-radius: 40px;
      text-decoration: none;
      font-size: 0.95rem;
      border: 1px solid #1a1a1a;
      transition: 0.2s;
  }

  .btn-primary:hover {
      background: #333;
  }

  .btn-secondary {
      background: transparent;
      color: #1a1a1a;
      padding: 0.8rem 2.2rem;
      border-radius: 40px;
      text-decoration: none;
      font-size: 0.95rem;
      border: 1px solid #c0c0c0;
      transition: 0.2s;
  }

  .btn-secondary:hover {
      border-color: #1a1a1a;
  }

  .btn-secondary.disabled,
  .btn-secondary:disabled {
      background: #f5f5f5;
      color: #aaa;
      padding: 0.8rem 2.2rem;
      border-radius: 40px;
      text-decoration: none;
      font-size: 0.95rem;
      border: 1px solid #e0e0e0;
      cursor: not-allowed;
      pointer-events: none;
      opacity: 0.8;
  }

  .btn-secondary.disabled:hover,
  .btn-secondary:disabled:hover {
      border-color: #e0e0e0;
      /* No hover change */
      background: #f5f5f5;
  }

  /* footer */
  .footer {
      margin-top: 4rem;
      font-size: 0.75rem;
      color: #8f8f8f;
      border-top: 1px solid #e2e2e2;
      padding-top: 2rem;
      text-align: center;
  }