body { background: var(--bg); }

  .nav {
    position: sticky; top: 0; z-index: 50;
    background: color-mix(in oklch, var(--bg) 92%, transparent);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--line);
  }
  .nav-inner {
    max-width: 1180px; margin: 0 auto;
    padding: 14px 32px;
    display: flex; align-items: center; justify-content: space-between;
  }
  .nav .brand { display: flex; align-items: center; gap: 10px; }
  .nav .brand .mark {
    width: 26px; height: 26px;
    background: var(--ink); color: var(--bg);
    font-family: var(--mono); font-weight: 700; font-size: 13px;
    display: grid; place-items: center;
    border-radius: 6px;
  }
  .nav .brand .name { font-weight: 600; font-size: 16px; }
  .nav .brand .sub {
    font-family: var(--mono); font-size: 12px;
    color: var(--muted); text-transform: uppercase; letter-spacing: 0.08em;
    margin-left: 8px; padding-left: 10px;
    border-left: 1px solid var(--line);
  }
  .nav .links { display: flex; align-items: center; gap: 6px; }
  .nav .link {
    font-family: var(--mono); font-size: 13px;
    color: var(--ink-2); text-transform: uppercase; letter-spacing: 0.08em;
    padding: 8px 12px; border-radius: var(--radius);
  }
  .nav .link:hover { background: var(--surface-3); text-decoration: none; }

  .page { max-width: 1180px; margin: 0 auto; padding: 0 32px; }

  .hero { padding: 72px 0 56px; }
  .hero h1 {
    font-size: clamp(32px, 4.5vw, 52px);
    line-height: 1.08; letter-spacing: -0.03em;
    font-weight: 600; margin: 0 0 16px;
    text-wrap: balance;
  }
  .hero-sub {
    font-size: 19px; color: var(--ink-3);
    line-height: 1.6; max-width: 680px; margin: 0 0 28px;
  }
  .hero-cta { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
  .btn-lg {
    background: var(--ink); color: #fff; border: 1px solid var(--ink);
    padding: 13px 22px; border-radius: var(--radius);
    font-family: var(--sans); font-size: 16px; font-weight: 500;
    cursor: pointer; text-decoration: none;
    display: inline-flex; align-items: center; gap: 8px;
  }
  .btn-lg:hover { background: var(--ink-2); border-color: var(--ink-2); text-decoration: none; }
  .btn-lg.ghost {
    background: transparent; color: var(--ink); border-color: var(--line-2);
  }
  .btn-lg.ghost:hover { background: var(--surface-3); border-color: var(--line-strong); }

  .hero-stats {
    margin-top: 32px;
    display: grid; grid-template-columns: repeat(4, auto); gap: 0;
    border-top: 1px solid var(--line);
    padding-top: 18px;
    width: fit-content;
  }
  .hero-stats div { padding-right: 24px; }
  .hero-stats div + div { border-left: 1px solid var(--line); padding-left: 24px; }
  .hero-stats .num {
    font-family: var(--mono); font-size: 22px; font-weight: 500;
    color: var(--ink); letter-spacing: -0.01em;
    font-feature-settings: 'tnum';
  }
  .hero-stats .label {
    font-family: var(--mono); font-size: 11px; font-weight: 500;
    color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em;
    margin-top: 4px;
  }

  /* ── Domain sections ─────────────────────────────────────────────── */
  .domain {
    padding: 56px 0;
    border-bottom: 1px solid var(--line);
  }
  .domain:last-of-type { border-bottom: 0; }
  .domain-head {
    display: flex; align-items: baseline; gap: 16px; margin-bottom: 8px;
  }
  .domain-id {
    font-family: var(--mono); font-size: 12px; font-weight: 500;
    color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em;
  }
  .domain-weight {
    font-family: var(--mono); font-size: 13px;
    color: var(--accent-ink); font-weight: 600;
    margin-left: auto;
  }
  .domain h2 {
    font-size: clamp(22px, 2.5vw, 30px);
    font-weight: 600; margin: 0 0 8px;
    letter-spacing: -0.015em;
  }
  .domain-desc {
    font-size: 16px; color: var(--ink-3);
    line-height: 1.6; max-width: 700px; margin: 0 0 28px;
  }

  /* ── Task cards ──────────────────────────────────────────────────── */
  .task-list {
    display: grid; gap: 14px;
  }
  .task {
    border: 1px solid var(--line);
    background: var(--surface);
    border-radius: var(--radius);
    padding: 22px 24px;
  }
  .task-head {
    display: flex; align-items: center; gap: 12px;
    margin-bottom: 8px;
  }
  .task-num {
    font-family: var(--mono); font-size: 11px; font-weight: 600;
    color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em;
    background: var(--surface-2); padding: 3px 8px; border-radius: 4px;
    white-space: nowrap;
  }
  .task h3 {
    font-size: 18px; font-weight: 600; margin: 0;
    letter-spacing: -0.01em;
  }
  .task-body {
    font-size: 15px; color: var(--ink-3);
    line-height: 1.6; margin: 0 0 12px;
    max-width: 700px;
  }
  .task-skills {
    display: flex; flex-wrap: wrap; gap: 6px;
  }
  .task-skills span {
    font-family: var(--mono); font-size: 12px;
    color: var(--muted); background: var(--surface-2);
    padding: 3px 10px; border-radius: 4px;
    letter-spacing: 0.04em;
  }

  /* ── CTA ─────────────────────────────────────────────────────────── */
  .cta-section {
    padding: 72px 0 88px;
    text-align: center;
  }
  .cta-section h2 {
    font-size: clamp(24px, 3vw, 36px);
    font-weight: 600; margin: 0 0 12px;
    letter-spacing: -0.02em;
  }
  .cta-section p {
    font-size: 17px; color: var(--ink-3);
    line-height: 1.6; max-width: 540px; margin: 0 auto 24px;
  }

  /* ── Footer ──────────────────────────────────────────────────────── */
  .foot {
    border-top: 1px solid var(--line);
    padding: 22px 0;
    font-family: var(--mono); font-size: 12px;
    color: var(--muted); letter-spacing: 0.04em;
  }
  .foot-inner {
    max-width: 1180px; margin: 0 auto; padding: 0 32px;
    display: flex; align-items: center; justify-content: space-between;
    flex-wrap: wrap; gap: 12px;
  }
  .foot .links { display: flex; gap: 18px; }
  .foot .links a { color: var(--muted); }
  .foot .links a:hover { color: var(--ink); }

  /* ── Responsive ──────────────────────────────────────────────────── */
  @media (max-width: 768px) {
    .hero-stats { grid-template-columns: repeat(2, 1fr); gap: 14px; width: auto; }
    .hero-stats div + div { border-left: none; padding-left: 0; }
    .nav .links .link.hide-mobile { display: none; }
  }

  /* ── Cert switcher (added for multi-cert topics) ──────────────────── */
  .cert-switch { display:inline-flex; align-items:center; border:1px solid var(--line-2); border-radius:var(--radius); overflow:hidden; margin-right:6px; }
  .cert-switch a { font-family:var(--mono); font-size:12px; font-weight:500; text-transform:uppercase; letter-spacing:0.08em; color:var(--ink-3); padding:7px 12px; text-decoration:none; border-right:1px solid var(--line); }
  .cert-switch a:last-child { border-right:0; }
  .cert-switch a:hover { background:var(--surface-3); text-decoration:none; }
  .cert-switch a.active { background:var(--ink); color:#fff; }
  .task .docs-chip { display:inline-block; margin-top:10px; font-family:var(--mono); font-size:12px; color:var(--accent-ink); }