:root {
    --ink: #0a0f14;
    --ink-2: #0f1620;
    --surface: #131c27;
    --surface-2: #1a2532;
    --surface-3: #233040;
    --border: #243345;
    --border-soft: #1b2532;
    --text: #e8edf3;
    --text-soft: #b4c2d0;
    --text-mute: #7e8e9d;
    --flow: #14b8a6;       /* primary accent */
    --flow-2: #06b6d4;
    --fire: #f59e0b;       /* secondary / sub-routes */
    --fire-2: #fb923c;
    --danger: #ef4444;
    --success: #22c55e;
    --indigo: #818cf8;     /* current location / active branch */
    --indigo-2: #6366f1;
    --serif: 'Fraunces', Georgia, serif;
    --sans: 'Manrope', system-ui, sans-serif;
    --mono: 'JetBrains Mono', ui-monospace, monospace;
  }

  * { box-sizing: border-box; margin: 0; padding: 0; }
  html { scroll-behavior: smooth; }
  body {
    font-family: var(--sans); background: var(--ink); color: var(--text);
    line-height: 1.6; font-size: 16px; overflow-x: hidden; -webkit-font-smoothing: antialiased;
  }
  :focus-visible { outline: 2px solid var(--indigo); outline-offset: 2px; border-radius: 4px; }

  .bg-deco {
    position: fixed; inset: 0; z-index: -1; pointer-events: none;
    background:
      radial-gradient(ellipse 80% 50% at 50% -10%, rgba(129, 140, 248, 0.07), transparent 60%),
      radial-gradient(ellipse 60% 40% at 100% 60%, rgba(20, 184, 166, 0.05), transparent 60%),
      var(--ink);
  }
  .bg-deco::before {
    content: ''; position: absolute; inset: 0;
    background-image:
      linear-gradient(rgba(36, 51, 69, 0.22) 1px, transparent 1px),
      linear-gradient(90deg, rgba(36, 51, 69, 0.22) 1px, transparent 1px);
    background-size: 64px 64px;
    mask-image: radial-gradient(ellipse 80% 60% at 50% 30%, black 30%, transparent 80%);
  }

  .wrap { max-width: 1240px; margin: 0 auto; padding: 0 32px; }

  /* ===== Shared site bar ===== */
  .sitebar { position: sticky; top: 0; z-index: 60; backdrop-filter: blur(14px); background: rgba(10, 15, 20, 0.85); border-bottom: 1px solid var(--border-soft); }
  .sitebar-inner { max-width: 1240px; margin: 0 auto; padding: 12px 32px; display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
  .site-brand { display: flex; align-items: center; gap: 10px; font-family: var(--serif); font-weight: 600; font-style: italic; font-size: 16px; color: var(--text); text-decoration: none; white-space: nowrap; }
  .site-mark { width: 24px; height: 24px; border-radius: 7px; background: linear-gradient(135deg, var(--flow), var(--indigo-2)); position: relative; overflow: hidden; flex-shrink: 0; }
  .site-mark::after { content: ''; position: absolute; inset: 0; background: radial-gradient(circle at 30% 30%, rgba(255,255,255,0.5), transparent 60%); }
  .site-links { display: flex; gap: 4px; flex-wrap: wrap; }
  .site-links a { font-family: var(--sans); font-size: 13px; color: var(--text-mute); text-decoration: none; padding: 6px 12px; border-radius: 8px; transition: all 0.18s; white-space: nowrap; }
  .site-links a:hover { color: var(--text); background: rgba(255,255,255,0.04); }
  .site-links a.active { color: var(--flow); background: rgba(20,184,166,0.1); font-weight: 600; }
  @media (max-width: 720px) { .site-links a { padding: 6px 9px; font-size: 12px; } .site-brand span:not(.site-mark) { display: none; } }

  .topbar {
    position: sticky; top: 0; z-index: 50; backdrop-filter: blur(14px);
    background: rgba(10, 15, 20, 0.78); border-bottom: 1px solid var(--border-soft);
  }
  .topbar-inner {
    display: flex; align-items: center; justify-content: space-between;
    padding: 14px 32px; max-width: 1240px; margin: 0 auto; gap: 24px; flex-wrap: wrap;
  }
  .brand {
    display: flex; align-items: center; gap: 12px;
    font-family: var(--serif); font-weight: 600; font-style: italic; font-size: 18px;
  }
  .brand-mark {
    width: 28px; height: 28px; border-radius: 8px;
    background: linear-gradient(135deg, var(--indigo), var(--flow));
    position: relative; overflow: hidden;
  }
  .brand-mark::after {
    content: ''; position: absolute; inset: 0;
    background: radial-gradient(circle at 30% 30%, rgba(255,255,255,0.5), transparent 60%);
  }
  .topnav { display: flex; gap: 20px; font-size: 13px; color: var(--text-soft); flex-wrap: wrap; }
  .topnav a { color: inherit; text-decoration: none; transition: color 0.2s; }
  .topnav a:hover { color: var(--indigo); }
  @media (max-width: 980px) { .topnav { display: none; } }

  /* Hero */
  .hero { padding: 96px 0 72px; position: relative; }
  .eyebrow {
    display: inline-flex; align-items: center; gap: 10px;
    padding: 6px 14px; border: 1px solid var(--border); border-radius: 999px;
    font-family: var(--mono); font-size: 11px; letter-spacing: 0.1em;
    text-transform: uppercase; color: var(--text-soft); margin-bottom: 32px;
  }
  .eyebrow::before {
    content: ''; width: 6px; height: 6px; border-radius: 50%;
    background: var(--indigo); box-shadow: 0 0 0 4px rgba(129, 140, 248, 0.15);
  }
  h1.title {
    font-family: var(--serif); font-weight: 500;
    font-size: clamp(44px, 6.6vw, 90px); line-height: 0.98;
    letter-spacing: -0.04em; margin-bottom: 28px;
  }
  h1.title em { font-style: italic; font-weight: 400; color: var(--indigo); }
  .lede {
    font-size: clamp(18px, 1.6vw, 22px); color: var(--text-soft);
    max-width: 700px; line-height: 1.5; margin-bottom: 36px;
  }

  /* URL bar motif */
  .urlbar {
    display: inline-flex; align-items: center; gap: 12px;
    background: var(--ink-2); border: 1px solid var(--border);
    border-radius: 12px; padding: 12px 18px; margin-bottom: 40px;
    font-family: var(--mono); font-size: 14px; max-width: 100%;
  }
  .urlbar .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--indigo); flex-shrink: 0; }
  .urlbar .path { color: var(--text); }
  .urlbar .path .seg-param { color: var(--fire); }
  .urlbar .caret {
    display: inline-block; width: 2px; height: 16px; background: var(--indigo);
    margin-left: 2px; vertical-align: middle; animation: blink 1.1s step-end infinite;
  }
  @keyframes blink { 50% { opacity: 0; } }

  .hero-meta {
    display: flex; gap: 40px; flex-wrap: wrap;
    padding-top: 32px; border-top: 1px solid var(--border-soft);
  }
  .meta-item .label {
    font-family: var(--mono); font-size: 10px; letter-spacing: 0.1em;
    text-transform: uppercase; color: var(--text-mute); margin-bottom: 4px;
  }
  .meta-item .value { font-family: var(--serif); font-size: 18px; color: var(--text); }

  section.chapter { padding: 96px 0; position: relative; }
  .chapter-num {
    font-family: var(--mono); font-size: 12px; letter-spacing: 0.15em;
    color: var(--indigo); margin-bottom: 16px; display: flex; align-items: center; gap: 12px;
  }
  .chapter-num::after {
    content: ''; flex: 1; height: 1px;
    background: linear-gradient(to right, var(--indigo), transparent); opacity: 0.35;
  }
  h2.chapter-title {
    font-family: var(--serif); font-weight: 500;
    font-size: clamp(34px, 4.4vw, 54px); line-height: 1.02;
    letter-spacing: -0.03em; margin-bottom: 24px; max-width: 820px;
  }
  h2.chapter-title em { font-style: italic; color: var(--flow); font-weight: 400; }
  .chapter-intro { font-size: 18px; color: var(--text-soft); max-width: 740px; margin-bottom: 48px; }
  h3 { font-family: var(--serif); font-weight: 500; font-size: 27px; letter-spacing: -0.02em; margin: 40px 0 16px; }
  h4 {
    font-family: var(--sans); font-weight: 600; font-size: 12px; letter-spacing: 0.1em;
    text-transform: uppercase; color: var(--indigo); margin: 28px 0 12px;
  }
  p { margin-bottom: 16px; color: var(--text-soft); }
  p strong { color: var(--text); font-weight: 600; }

  pre.code-block {
    background: var(--ink-2); border: 1px solid var(--border);
    border-radius: 12px; padding: 24px 28px;
    font-family: var(--mono); font-size: 13px; line-height: 1.7;
    overflow-x: auto; margin: 16px 0; position: relative;
    white-space: pre; color: var(--text-soft); tab-size: 2;
  }
  pre.code-block::before {
    content: attr(data-lang); position: absolute; top: 12px; right: 16px;
    font-size: 10px; color: var(--text-mute); letter-spacing: 0.1em;
    text-transform: uppercase; background: var(--ink-2); padding: 2px 4px;
  }
  pre.code-block .kw   { color: #c084fc; }
  pre.code-block .typ  { color: var(--flow); }
  pre.code-block .str  { color: var(--fire-2); }
  pre.code-block .num  { color: #fbbf24; }
  pre.code-block .com  { color: var(--text-mute); font-style: italic; }
  pre.code-block .fn   { color: #60a5fa; }
  pre.code-block .anno { color: var(--success); }
  pre.code-block .cst  { color: var(--indigo); }   /* route constants */
  pre.code-block .bad  { color: var(--danger); }

  .two-up { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; margin: 32px 0; }
  @media (max-width: 760px) { .two-up { grid-template-columns: 1fr; } }
  .card { padding: 32px; background: var(--surface); border: 1px solid var(--border); border-radius: 16px; position: relative; }
  .card.bad  { border-color: rgba(239, 68, 68, 0.3); }
  .card.good { border-color: rgba(20, 184, 166, 0.3); }
  .card-tag {
    font-family: var(--mono); font-size: 10px; text-transform: uppercase;
    letter-spacing: 0.1em; color: var(--danger); margin-bottom: 8px;
  }
  .card.good .card-tag { color: var(--flow); }
  .card-title { font-family: var(--serif); font-size: 22px; margin-bottom: 12px; }

  /* Tree explorer */
  .tax-wrap { display: grid; grid-template-columns: 0.95fr 1.05fr; gap: 28px; align-items: start; margin: 32px 0; }
  @media (max-width: 900px) { .tax-wrap { grid-template-columns: 1fr; } }
  .tree {
    background: var(--surface); border: 1px solid var(--border);
    border-radius: 16px; padding: 24px; font-family: var(--mono); font-size: 13px;
    line-height: 1.5; overflow-x: auto;
  }
  .tree-node {
    display: block; width: 100%; text-align: left; background: transparent;
    border: 1px solid transparent; color: var(--text-soft);
    padding: 7px 10px; border-radius: 8px; cursor: pointer;
    transition: all 0.18s; font-family: var(--mono); font-size: 13px;
  }
  .tree-node:hover { border-color: var(--border); color: var(--text); }
  .tree-node.active { border-color: var(--indigo); background: rgba(129,140,248,0.08); color: var(--indigo); }
  .tree-node .tn-kind { color: var(--text-mute); font-size: 11px; }
  .tree-node.shell .tn-label { color: var(--fire); }
  .tree-node.branch .tn-label { color: var(--indigo); }
  .tree-indent { color: var(--text-mute); }
  .tax-panel { background: var(--surface); border: 1px solid var(--border); border-radius: 16px; padding: 28px; position: sticky; top: 90px; }
  .tax-panel .scope-pill {
    display: inline-block; font-family: var(--mono); font-size: 10px;
    padding: 4px 10px; border-radius: 6px; margin-bottom: 12px;
    letter-spacing: 0.1em; text-transform: uppercase;
    background: rgba(129,140,248,0.15); color: var(--indigo);
  }
  .tax-panel h4.tp-title { margin: 0 0 6px; color: var(--text); font-family: var(--serif); font-size: 22px; text-transform: none; letter-spacing: -0.01em; }
  .tax-panel p { font-size: 14px; }
  .tax-panel pre.code-block { margin-top: 14px; }

  /* Demo shell */
  .demo { margin: 32px 0; border: 1px solid var(--border); border-radius: 18px; overflow: hidden; background: var(--surface); }
  .demo-head {
    display: flex; align-items: center; justify-content: space-between;
    padding: 16px 24px; border-bottom: 1px solid var(--border-soft); background: var(--ink-2);
  }
  .demo-head .dot-group { display: flex; gap: 6px; }
  .demo-head .dot { width: 10px; height: 10px; border-radius: 50%; background: var(--surface-3); }
  .demo-head .title-pill { font-family: var(--mono); font-size: 11px; letter-spacing: 0.1em; color: var(--text-mute); text-transform: uppercase; }
  .demo-grid { display: grid; grid-template-columns: 1fr 1fr; }
  @media (max-width: 900px) { .demo-grid { grid-template-columns: 1fr; } }
  .demo-pane { padding: 28px; }
  .demo-pane.left {
    border-right: 1px solid var(--border-soft);
    background: radial-gradient(ellipse at top, rgba(129,140,248,0.05), transparent 60%), var(--ink-2);
    display: flex; flex-direction: column; align-items: center; gap: 18px;
  }
  @media (max-width: 900px) { .demo-pane.left { border-right: none; border-bottom: 1px solid var(--border-soft); } }

  /* Phone */
  .phone {
    width: 100%; max-width: 300px; border: 1px solid var(--border);
    border-radius: 28px; background: var(--ink); overflow: hidden;
    display: flex; flex-direction: column; box-shadow: 0 12px 40px rgba(0,0,0,0.4);
  }
  .phone-status {
    padding: 10px 16px 8px; border-bottom: 1px solid var(--border-soft);
    font-family: var(--mono); font-size: 10px; color: var(--text-mute);
    display: flex; justify-content: space-between; align-items: center;
  }
  .phone-status .loc { color: var(--indigo); }
  .phone-body {
    min-height: 230px; padding: 22px 20px; display: flex; flex-direction: column;
    align-items: center; justify-content: center; gap: 14px; text-align: center;
    position: relative;
  }
  .phone-screen-name { font-family: var(--mono); font-size: 11px; color: var(--text-mute); letter-spacing: 0.1em; }
  .phone-title { font-family: var(--serif); font-size: 26px; color: var(--text); }
  .phone-count { font-family: var(--serif); font-size: 52px; line-height: 1; color: var(--indigo); transition: transform 0.2s, color 0.2s; }
  .phone-count.bump { transform: scale(1.12); color: var(--flow); }
  .phone-actions { display: flex; gap: 8px; flex-wrap: wrap; justify-content: center; margin-top: 4px; }
  .phone-detail-banner {
    font-family: var(--mono); font-size: 10px; color: var(--fire);
    background: rgba(245,158,11,0.1); border: 1px solid rgba(245,158,11,0.3);
    padding: 3px 8px; border-radius: 5px; letter-spacing: 0.1em;
  }
  .phone-nav { display: flex; border-top: 1px solid var(--border-soft); background: var(--ink-2); }
  .phone-nav button {
    flex: 1; background: transparent; border: none; color: var(--text-mute);
    padding: 12px 4px 14px; font-family: var(--sans); font-size: 11px; font-weight: 600;
    cursor: pointer; transition: all 0.2s; display: flex; flex-direction: column; align-items: center; gap: 4px;
    border-top: 2px solid transparent;
  }
  .phone-nav button .nav-ico { font-size: 16px; line-height: 1; }
  .phone-nav button:hover { color: var(--text-soft); }
  .phone-nav button.active { color: var(--indigo); border-top-color: var(--indigo); background: rgba(129,140,248,0.06); }

  .toggle-pill {
    display: inline-flex; align-items: center; gap: 8px;
    font-family: var(--mono); font-size: 11px; color: var(--text-soft);
    background: var(--ink); border: 1px solid var(--border);
    border-radius: 999px; padding: 6px 8px 6px 14px;
  }
  .toggle-pill .switch {
    width: 40px; height: 22px; border-radius: 999px; background: var(--surface-3);
    position: relative; cursor: pointer; transition: background 0.2s; border: none;
  }
  .toggle-pill .switch.on { background: var(--flow); }
  .toggle-pill .switch::after {
    content: ''; position: absolute; top: 2px; left: 2px; width: 18px; height: 18px;
    border-radius: 50%; background: white; transition: transform 0.2s;
  }
  .toggle-pill .switch.on::after { transform: translateX(18px); }

  .console {
    background: #050a10; border: 1px solid var(--border); border-radius: 12px;
    padding: 14px 16px; font-family: var(--mono); font-size: 11px; line-height: 1.7;
    height: 110px; overflow-y: auto; color: var(--text-soft); width: 100%;
  }
  .console .log-time { color: var(--text-mute); }
  .console .log-tag { color: var(--indigo); }
  .console .log-tag.warn { color: var(--fire); }
  .console .log-tag.ok { color: var(--flow); }
  .console .log-line { opacity: 0; animation: logIn 0.3s forwards; }
  @keyframes logIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: translateY(0); } }

  .demo-pane.right { background: var(--ink-2); padding: 0; }
  .demo-pane.right pre.code-block { margin: 0; border: none; border-radius: 0; min-height: 100%; background: transparent; }

  .btn {
    display: inline-flex; align-items: center; gap: 8px; padding: 10px 20px;
    background: var(--indigo); color: var(--ink); border: none; border-radius: 10px;
    font-family: var(--sans); font-weight: 600; font-size: 14px; cursor: pointer; transition: all 0.2s;
  }
  .btn:hover { background: var(--indigo-2); color: white; transform: translateY(-1px); }
  .btn.ghost { background: transparent; color: var(--text-soft); border: 1px solid var(--border); }
  .btn.ghost:hover { border-color: var(--indigo); color: var(--indigo); background: rgba(129,140,248,0.05); }
  .btn.small { padding: 8px 14px; font-size: 12px; }
  .btn.flow { background: var(--flow); color: var(--ink); }
  .btn.flow:hover { background: var(--flow-2); }

  /* Local toggle */
  .toggle-scope .toggle-head {
    display: inline-flex; align-items: center; gap: 6px; padding: 4px; padding-left: 14px;
    background: var(--ink-2); border: 1px solid var(--border); border-radius: 10px; margin: 8px 0 4px;
  }
  .toggle-scope .toggle-head .lbl {
    font-family: var(--mono); font-size: 10px; color: var(--text-mute);
    letter-spacing: 0.15em; text-transform: uppercase; margin-right: 4px;
  }
  .toggle-scope .toggle-head button {
    background: transparent; border: none; color: var(--text-mute);
    padding: 6px 12px; border-radius: 6px; font-family: var(--mono);
    font-size: 11px; cursor: pointer; transition: all 0.2s; white-space: nowrap;
  }
  .toggle-scope .toggle-head button:hover { color: var(--text); }
  .toggle-scope .toggle-head button.active { background: var(--indigo); color: var(--ink); font-weight: 600; }
  .toggle-scope .show-a, .toggle-scope .show-b { display: none; }
  .toggle-scope[data-mode="a"] .show-a { display: block; }
  .toggle-scope[data-mode="b"] .show-b { display: block; }

  .ref-table { width: 100%; border-collapse: separate; border-spacing: 0; margin: 24px 0; font-size: 14px; }
  .ref-table th, .ref-table td { text-align: left; padding: 15px 18px; border-bottom: 1px solid var(--border-soft); vertical-align: top; }
  .ref-table th { font-family: var(--mono); font-size: 11px; color: var(--text-mute); text-transform: uppercase; letter-spacing: 0.1em; font-weight: 500; border-bottom: 1px solid var(--border); }
  .ref-table td:first-child { font-family: var(--mono); font-size: 12.5px; color: var(--indigo); width: 32%; }
  .ref-table td { color: var(--text-soft); }

  .pitfall { padding: 22px 26px; border-left: 3px solid var(--fire); background: rgba(245,158,11,0.04); border-radius: 0 12px 12px 0; margin: 16px 0; }
  .pitfall .tag { font-family: var(--mono); font-size: 10px; text-transform: uppercase; letter-spacing: 0.15em; color: var(--fire); margin-bottom: 6px; }
  .pitfall h4 { color: var(--text); font-family: var(--serif); text-transform: none; letter-spacing: -0.01em; font-size: 18px; margin: 0 0 8px; }
  .pitfall p { font-size: 14px; margin: 0; }

  .callout { background: var(--surface); border: 1px solid var(--border); border-left: 3px solid var(--indigo); border-radius: 0 12px 12px 0; padding: 20px 24px; margin: 24px 0; }
  .callout.warn { border-left-color: var(--fire); }
  .callout .co-tag { font-family: var(--mono); font-size: 10px; text-transform: uppercase; letter-spacing: 0.15em; color: var(--indigo); margin-bottom: 8px; }
  .callout.warn .co-tag { color: var(--fire); }
  .callout p { font-size: 14px; margin: 0; color: var(--text-soft); }
  .callout p + p { margin-top: 10px; }

  ul.bullet { list-style: none; margin: 16px 0; }
  ul.bullet li { padding-left: 24px; position: relative; margin-bottom: 10px; color: var(--text-soft); font-size: 15px; }
  ul.bullet li::before { content: ''; position: absolute; left: 0; top: 10px; width: 8px; height: 8px; border: 1px solid var(--indigo); transform: rotate(45deg); }

  .inline-code { font-family: var(--mono); font-size: 0.9em; background: var(--surface-2); padding: 2px 6px; border-radius: 4px; color: var(--indigo); }

  .divider { height: 1px; background: linear-gradient(to right, transparent, var(--border), transparent); margin: 56px 0; }

  footer { padding: 80px 0 60px; border-top: 1px solid var(--border-soft); margin-top: 56px; text-align: center; }
  footer .closer { font-family: var(--serif); font-style: italic; font-size: 27px; color: var(--text); max-width: 600px; margin: 0 auto 24px; line-height: 1.3; }
  footer .signoff { font-family: var(--mono); font-size: 11px; color: var(--text-mute); letter-spacing: 0.1em; text-transform: uppercase; }

  @media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; transition-duration: 0.001ms !important; }
  }