:root {
      --background: #0b0d10;
      --surface: #12161b;
      --surface-soft: #171c22;
      --text: #edf0f3;
      --muted: #aab3bd;
      --border: #2a323b;
      --accent: #d8dde3;
      --max-width: 900px;
    }

    * {
      box-sizing: border-box;
    }

    html {
      scroll-behavior: smooth;
    }

    body {
      margin: 0;
      background: var(--background);
      color: var(--text);
      font-family: Inter, Arial, Helvetica, sans-serif;
      font-size: 17px;
      line-height: 1.7;
    }

    a {
      color: var(--accent);
      text-decoration-thickness: 1px;
      text-underline-offset: 4px;
    }

    a:hover,
    a:focus {
      text-decoration-thickness: 2px;
    }

    .page {
      width: min(100% - 40px, var(--max-width));
      margin: 0 auto;
      padding: 72px 0 96px;
    }

    .eyebrow {
      margin: 0 0 16px;
      color: var(--muted);
      font-size: 0.8rem;
      font-weight: 700;
      letter-spacing: 0.14em;
      text-transform: uppercase;
    }

    h1,
    h2 {
      line-height: 1.2;
    }

    h1 {
      max-width: 760px;
      margin: 0;
      font-size: clamp(2.7rem, 7vw, 5.5rem);
      font-weight: 700;
      letter-spacing: -0.05em;
    }

    h2 {
      margin: 0 0 22px;
      font-size: clamp(1.55rem, 4vw, 2.3rem);
      letter-spacing: -0.025em;
    }

    p {
      margin: 0 0 18px;
    }

    .intro {
      max-width: 760px;
      margin-top: 30px;
      color: var(--muted);
      font-size: clamp(1.12rem, 2.5vw, 1.35rem);
    }

    .notice {
      margin-top: 42px;
      padding: 24px 26px;
      border: 1px solid var(--border);
      background: var(--surface);
      border-radius: 14px;
    }

    section {
      padding-top: 72px;
    }

    .books {
      margin: 28px 0 0;
      padding: 0;
      list-style: none;
      counter-reset: books;
      display: grid;
      gap: 14px;
    }

    .books > li {
      counter-increment: books;
      display: grid;
      grid-template-columns: 44px 1fr;
      gap: 14px;
      align-items: start;
      padding: 19px 20px;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 12px;
    }

    .books > li::before {
      content: counter(books, decimal-leading-zero);
      color: var(--muted);
      font-size: 0.88rem;
      font-weight: 700;
      letter-spacing: 0.05em;
      padding-top: 2px;
    }

    .books a {
      font-weight: 650;
    }

    .guidance,
    .questions {
      padding-left: 1.25rem;
    }

    .guidance li,
    .questions li {
      margin-bottom: 12px;
    }

    .knowledge-map {
      display: grid;
      grid-template-columns: repeat(4, minmax(120px, 1fr));
      gap: 12px;
      margin-top: 26px;
    }

    .knowledge-map span {
      display: flex;
      min-height: 84px;
      align-items: center;
      justify-content: center;
      padding: 14px;
      text-align: center;
      background: var(--surface-soft);
      border: 1px solid var(--border);
      border-radius: 12px;
      font-weight: 650;
    }

    .resources {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      margin-top: 26px;
    }

    .resources a {
      display: inline-block;
      padding: 12px 16px;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 10px;
      text-decoration: none;
      font-weight: 650;
    }

    footer {
      margin-top: 80px;
      padding-top: 28px;
      border-top: 1px solid var(--border);
      color: var(--muted);
      font-size: 0.92rem;
    }

    @media (max-width: 680px) {
      .page {
        width: min(100% - 28px, var(--max-width));
        padding-top: 46px;
      }

      section {
        padding-top: 56px;
      }

      .knowledge-map {
        grid-template-columns: repeat(2, minmax(110px, 1fr));
      }
    }
  
    .book-card {
      padding: 24px;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 14px;
    }

    .book-card h3 {
      margin: 0 0 14px;
      font-size: 1.3rem;
      line-height: 1.3;
    }

    .book-card p {
      margin-bottom: 14px;
    }

    .book-meta {
      display: grid;
      gap: 8px;
      margin: 18px 0 0;
      padding: 0;
      list-style: none;
    }

    .book-meta li {
      display: block;
      padding: 0;
      border: 0;
      background: transparent;
    }

    .book-meta li::before {
      content: none;
    }

    .book-links {
      display: flex;
      flex-wrap: wrap;
      gap: 12px;
      margin-top: 18px;
    }

    .book-links a {
      display: inline-block;
      padding: 10px 14px;
      border: 1px solid var(--border);
      border-radius: 9px;
      text-decoration: none;
      font-weight: 650;
    }

    .footer-nav {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: 10px;
      margin: 0 0 18px;
      font-size: 0.92rem;
    }

    .footer-nav a {
      color: var(--muted);
      text-decoration: none;
    }

    .footer-nav a:hover,
    .footer-nav a:focus {
      color: var(--text);
      text-decoration: underline;
    }

    .footer-nav a[aria-current="page"] {
      color: var(--text);
    }

    .footer-nav span {
      opacity: .4;
    }