:root {
      color-scheme: light;
      --text: #151515;
      --muted: #4a4a4a;
      --border: #d4d4d4;
      --border-light: #eaeaea;
      --surface: #ffffff;
      --surface-alt: #f7f8f8;
      --surface-sidebar: #fafbfc;
      --brand: #0079c1;
      --brand-dark: #005e95;
      --brand-light: #e6f1f8;
      --warning: #8a5200;
      --warning-bg: #fff8e8;
      --success: #356b21;
      --success-bg: #edf5e8;
      --sidebar-width: 17rem;
      --header-height: 4rem;
    }

    * {
      box-sizing: border-box;
    }

    html {
      scroll-behavior: smooth;
      scroll-padding-top: calc(var(--header-height) + 1rem);
    }

    body {
      margin: 0;
      color: var(--text);
      background: var(--surface);
      font-family: "Avenir Next", Avenir, "Helvetica Neue", Arial, sans-serif;
      font-size: 1rem;
      line-height: 1.6;
    }

    a {
      color: var(--brand);
    }

    a:hover,
    a:focus-visible {
      color: var(--brand-dark);
    }

    /* ---------- Skip link ---------- */
    .skip-link {
      position: absolute;
      left: 1rem;
      top: -4rem;
      z-index: 100;
      padding: 0.5rem 0.75rem;
      background: var(--surface);
      border: 2px solid var(--brand);
    }

    .skip-link:focus {
      top: 1rem;
    }

    /* ---------- Top header ---------- */
    .site-header {
      position: sticky;
      top: 0;
      z-index: 10;
      height: var(--header-height);
      display: flex;
      align-items: center;
      border-bottom: 1px solid var(--border);
      background: var(--surface);
      padding: 0 1.5rem;
    }

    .site-header .brand-title {
      font-size: 1.05rem;
      font-weight: 600;
      color: var(--text);
      text-decoration: none;
    }

    .site-header .brand-title span {
      color: var(--muted);
      font-weight: 400;
    }

    .site-header .header-spacer {
      flex: 1;
    }

    .site-header .back-link {
      font-size: 0.9rem;
      text-decoration: none;
    }

    /* ---------- Two-column layout ---------- */
    .layout {
      display: grid;
      grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
      align-items: start;
      max-width: 80rem;
      margin: 0 auto;
    }

    .sidebar {
      position: sticky;
      top: var(--header-height);
      align-self: start;
      height: calc(100vh - var(--header-height));
      overflow-y: auto;
      padding: 1.5rem 1rem 2rem 1.5rem;
      border-right: 1px solid var(--border-light);
      background: var(--surface-sidebar);
      font-size: 0.93rem;
    }

    .sidebar h2 {
      margin: 0 0 0.5rem;
      font-size: 0.75rem;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.05em;
      color: var(--muted);
    }

    .sidebar ul {
      list-style: none;
      padding: 0;
      margin: 0 0 1.25rem;
    }

    .sidebar > ul > li > a {
      display: block;
      padding: 0.3rem 0.5rem;
      margin: 0.1rem 0;
      border-radius: 0.25rem;
      color: var(--text);
      text-decoration: none;
      font-weight: 500;
    }

    .sidebar > ul > li > a:hover,
    .sidebar > ul > li > a:focus-visible {
      background: var(--brand-light);
      color: var(--brand-dark);
    }

    .sidebar ul ul {
      padding-left: 0.75rem;
      margin: 0 0 0.4rem;
      border-left: 2px solid var(--border-light);
    }

    .sidebar ul ul a {
      display: block;
      padding: 0.2rem 0.5rem;
      font-size: 0.88rem;
      color: var(--muted);
      text-decoration: none;
    }

    .sidebar ul ul a:hover,
    .sidebar ul ul a:focus-visible {
      color: var(--brand-dark);
    }

    /* ---------- Content column ---------- */
    .content {
      min-width: 0;
      padding: 2rem 2.5rem 4rem;
    }

    .content > section {
      padding: 1.5rem 0 2rem;
      border-bottom: 1px solid var(--border-light);
    }

    .content > section:last-child {
      border-bottom: 0;
    }

    .content h1 {
      margin: 0 0 0.5rem;
      font-size: clamp(1.75rem, 3vw, 2.25rem);
      font-weight: 500;
      line-height: 1.2;
    }

    .content h2 {
      margin: 0 0 0.75rem;
      font-size: 1.5rem;
      font-weight: 500;
      line-height: 1.25;
    }

    .content h3 {
      margin: 1.5rem 0 0.5rem;
      font-size: 1.15rem;
      font-weight: 600;
    }

    .content h4 {
      margin: 1.25rem 0 0.4rem;
      font-size: 1rem;
      font-weight: 600;
    }

    .content p {
      margin: 0.6rem 0;
      max-width: 58rem;
    }

    .content ol,
    .content ul {
      max-width: 62rem;
      padding-left: 1.4rem;
      margin: 0.6rem 0;
    }

    .content li {
      margin: 0.35rem 0;
    }

    .lead {
      color: var(--muted);
      font-size: 1.1rem;
      max-width: 54rem;
    }

    code {
      padding: 0.1rem 0.3rem;
      border-radius: 0.2rem;
      background: #eeeeee;
      font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
      font-size: 0.92em;
    }

    /* ---------- Callouts ---------- */
    .callout {
      max-width: 58rem;
      margin: 1rem 0;
      padding: 0.75rem 1rem;
      border-left: 0.25rem solid var(--warning);
      background: var(--warning-bg);
      color: #3d2a00;
    }

    .callout.info {
      border-left-color: var(--brand);
      background: var(--brand-light);
      color: var(--brand-dark);
    }

    .callout.success {
      border-left-color: var(--success);
      background: var(--success-bg);
      color: var(--success);
    }

    .callout strong {
      display: block;
      margin-bottom: 0.2rem;
    }

    /* ---------- Compatibility cards ---------- */
    .summary-list {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
      gap: 1rem;
      padding: 0;
      margin: 1rem 0;
      list-style: none;
      max-width: 62rem;
    }

    .summary-list li {
      margin: 0;
      padding: 1rem;
      border: 1px solid var(--border);
      background: var(--surface-alt);
      border-radius: 0.3rem;
    }

    .summary-list strong {
      display: block;
      margin-bottom: 0.3rem;
      color: var(--text);
    }

    /* ---------- Tables ---------- */
    .data-table {
      width: 100%;
      max-width: 62rem;
      margin: 1rem 0;
      border-collapse: collapse;
      font-size: 0.95rem;
    }

    .data-table th,
    .data-table td {
      text-align: left;
      padding: 0.55rem 0.75rem;
      border-bottom: 1px solid var(--border-light);
      vertical-align: top;
    }

    .data-table th {
      background: var(--surface-alt);
      font-weight: 600;
    }

    /* ---------- FAQ collapsibles ---------- */
    .faq {
      max-width: 62rem;
    }

    .faq details {
      margin: 0.5rem 0;
      padding: 0.6rem 0.9rem;
      border: 1px solid var(--border-light);
      border-radius: 0.3rem;
      background: var(--surface-alt);
    }

    .faq details[open] {
      background: var(--surface);
      border-color: var(--border);
    }

    .faq summary {
      cursor: pointer;
      font-weight: 500;
      list-style: none;
      padding-right: 1.5rem;
      position: relative;
    }

    .faq summary::-webkit-details-marker {
      display: none;
    }

    .faq summary::after {
      content: "+";
      position: absolute;
      right: 0;
      top: 0;
      font-weight: 400;
      color: var(--muted);
      font-size: 1.2rem;
      line-height: 1;
    }

    .faq details[open] summary::after {
      content: "−";
    }

    .faq details > p,
    .faq details > ul {
      margin: 0.6rem 0 0.2rem;
    }

    /* ---------- Changelog ---------- */
    .changelog .entry {
      margin: 1rem 0;
      padding: 0.85rem 1rem;
      border-left: 0.25rem solid var(--border);
      background: var(--surface-alt);
      max-width: 62rem;
    }

    .changelog .entry h3 {
      margin: 0 0 0.3rem;
      font-size: 1rem;
    }

    .changelog .entry .date {
      color: var(--muted);
      font-size: 0.85rem;
      margin-left: 0.5rem;
      font-weight: 400;
    }

    .changelog .entry ul {
      margin: 0.4rem 0 0;
      padding-left: 1.4rem;
    }

    /* ---------- Footer ---------- */
    footer.site-footer {
      padding: 1.5rem 2.5rem 2rem;
      border-top: 1px solid var(--border);
      color: var(--muted);
      font-size: 0.88rem;
    }

    /* ---------- Responsive ---------- */
    @media (max-width: 900px) {
      .layout {
        grid-template-columns: 1fr;
      }

      .sidebar {
        position: static;
        height: auto;
        overflow: visible;
        border-right: 0;
        border-bottom: 1px solid var(--border-light);
        padding: 1rem 1.5rem;
      }

      .content {
        padding: 1.5rem 1.5rem 3rem;
      }
    }