:root {
    --bg: #EEF2F1;
    --bg-panel: #FFFFFF;
    --bg-panel-raised: #F7FAF9;
    --grid-line: rgba(20,32,43,0.07);
    --ink: #14202B;
    --ink-muted: #4B5A66;
    --ink-faint: #7C8B94;
    --accent: #C6841F;
    --accent-ink: #8B5A00;
    --accent-soft: rgba(198,132,31,0.14);
    --moss: #4F6B4A;
    --moss-soft: rgba(79,107,74,0.14);
    --border: rgba(20,32,43,0.18);
    --border-soft: rgba(20,32,43,0.10);
    --danger: #A6341B;
    --danger-soft: rgba(166,52,27,0.12);
    --font-display: 'Space Grotesk', 'Arial Narrow', Arial, sans-serif;
    --font-mono: 'IBM Plex Mono', 'SFMono-Regular', Consolas, 'Liberation Mono', monospace;
    --radius: 3px;
    --shadow: none;
  }
  @media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
      --bg: #0F1821;
      --bg-panel: #16212B;
      --bg-panel-raised: #1C2934;
      --grid-line: rgba(231,237,240,0.06);
      --ink: #E7EDF0;
      --ink-muted: #9FB0BA;
      --ink-faint: #6E828C;
      --accent: #E3A548;
      --accent-ink: #F4C878;
      --accent-soft: rgba(227,165,72,0.16);
      --moss: #86AC7E;
      --moss-soft: rgba(134,172,126,0.16);
      --border: rgba(231,237,240,0.18);
      --border-soft: rgba(231,237,240,0.10);
      --danger: #E2685A;
      --danger-soft: rgba(226,104,90,0.16);
    }
  }
  :root[data-theme="dark"] {
    --bg: #0F1821;
    --bg-panel: #16212B;
    --bg-panel-raised: #1C2934;
    --grid-line: rgba(231,237,240,0.06);
    --ink: #E7EDF0;
    --ink-muted: #9FB0BA;
    --ink-faint: #6E828C;
    --accent: #E3A548;
    --accent-ink: #F4C878;
    --accent-soft: rgba(227,165,72,0.16);
    --moss: #86AC7E;
    --moss-soft: rgba(134,172,126,0.16);
    --border: rgba(231,237,240,0.18);
    --border-soft: rgba(231,237,240,0.10);
    --danger: #E2685A;
    --danger-soft: rgba(226,104,90,0.16);
  }

  * { box-sizing: border-box; }
  html { scroll-behavior: smooth; }
  body {
    margin: 0;
    background:
      linear-gradient(var(--grid-line) 1px, transparent 1px) 0 0 / 28px 28px,
      linear-gradient(90deg, var(--grid-line) 1px, transparent 1px) 0 0 / 28px 28px,
      var(--bg);
    color: var(--ink);
    font-family: var(--font-mono);
    font-size: 16px;
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
  }
  h1, h2, h3, .disp {
    font-family: var(--font-display);
    color: var(--ink);
    line-height: 1.15;
    font-weight: 600;
    margin: 0 0 .5em;
  }
  a { color: var(--accent-ink); }
  p { max-width: 70ch; }
  :focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
  button, input, textarea, select { font-family: var(--font-mono); font-size: 15px; color: var(--ink); }
  @media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; } }

  /* ---- shell ---- */
  .shell { display: grid; grid-template-columns: 260px 1fr; min-height: 100vh; }
  .side {
    border-right: 1px solid var(--border);
    padding: 22px 18px 40px;
    position: sticky; top: 0; height: 100vh; overflow-y: auto;
    background: var(--bg-panel);
  }
  .brand { display: flex; align-items: baseline; gap: 8px; text-decoration: none; margin-bottom: 4px; }
  .brand-mark { font-family: var(--font-display); font-weight: 700; font-size: 22px; color: var(--ink); }
  .brand-tag { font-size: 11px; color: var(--ink-faint); }
  .side-sub { color: var(--ink-muted); font-size: 12.5px; margin: 4px 0 20px; line-height: 1.5; }
  .nav-group { margin-bottom: 18px; }
  .nav-group h3 { font-family: var(--font-mono); font-weight: 600; font-size: 11.5px; color: var(--ink-faint); margin: 0 0 6px; padding-left: 10px; }
  .nav-group ul { list-style: none; margin: 0; padding: 0; }
  .nav-link {
    display: block; text-decoration: none; color: var(--ink-muted);
    font-size: 14px; padding: 6px 10px; border-radius: var(--radius);
    border-left: 2px solid transparent;
  }
  .nav-link:hover { color: var(--ink); background: var(--bg-panel-raised); }
  .nav-link.active { color: var(--ink); border-left-color: var(--accent); background: var(--accent-soft); font-weight: 500; }
  .theme-btn {
    margin-top: 10px; width: 100%; padding: 8px 10px; background: transparent;
    border: 1px solid var(--border); border-radius: var(--radius); cursor: pointer; color: var(--ink-muted);
    font-size: 12.5px; text-align: left;
  }
  .theme-btn:hover { color: var(--ink); border-color: var(--ink-faint); }

  .main { min-width: 0; }
  .topbar {
    display: none; align-items: center; justify-content: space-between;
    padding: 14px 18px; border-bottom: 1px solid var(--border); background: var(--bg-panel);
    position: sticky; top: 0; z-index: 5;
  }
  .burger { background: none; border: 1px solid var(--border); border-radius: var(--radius); padding: 6px 10px; font-family: var(--font-mono); cursor: pointer; color: var(--ink); }

  .wrap { max-width: 880px; padding: 48px 40px 90px; margin: 0 auto; }
  .kicker { font-size: 12.5px; color: var(--moss); margin: 0 0 10px; }
  .page-head h1 { font-size: clamp(28px, 4vw, 38px); }
  .lede { color: var(--ink-muted); font-size: 16.5px; }

  .panel {
    position: relative;
    background: var(--bg-panel);
    border: 1px solid var(--border);
    padding: 22px;
    margin: 28px 0;
  }
  .panel::before, .panel::after,
  .panel .corner-br, .panel .corner-bl { display: none; }
  .panel { }
  .panel-tick { position: absolute; width: 9px; height: 9px; border: 1px solid var(--ink-faint); }
  .tick-tl { top: -1px; left: -1px; border-right: none; border-bottom: none; }
  .tick-tr { top: -1px; right: -1px; border-left: none; border-bottom: none; }
  .tick-bl { bottom: -1px; left: -1px; border-right: none; border-top: none; }
  .tick-br { bottom: -1px; right: -1px; border-left: none; border-top: none; }

  .field-label { display: block; font-size: 12.5px; color: var(--ink-faint); margin: 0 0 6px; }
  textarea, .tin {
    width: 100%; background: var(--bg-panel-raised); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 10px 12px; color: var(--ink); resize: vertical;
  }
  textarea:focus, .tin:focus { border-color: var(--accent); }
  .row { display: grid; gap: 16px; }
  .row.two { grid-template-columns: 1fr 1fr; }
  @media (max-width: 720px) { .row.two { grid-template-columns: 1fr; } }
  .controls { display: flex; flex-wrap: wrap; gap: 10px; margin: 14px 0; align-items: center; }
  .btn {
    background: var(--ink); color: var(--bg-panel); border: 1px solid var(--ink);
    padding: 9px 16px; border-radius: var(--radius); cursor: pointer; font-size: 14px; font-weight: 500;
  }
  .btn:hover { opacity: .88; }
  .btn.ghost { background: transparent; color: var(--ink); border-color: var(--border); }
  .btn.ghost:hover { border-color: var(--ink-faint); }
  .btn.accent { background: var(--accent); border-color: var(--accent); color: #1B1200; }
  select.tin { appearance: none; }
  .flags { display: flex; gap: 14px; flex-wrap: wrap; font-size: 13.5px; color: var(--ink-muted); }
  .flags label { display: flex; align-items: center; gap: 6px; }
  .out-error { color: var(--danger); background: var(--danger-soft); border: 1px solid var(--danger); border-radius: var(--radius); padding: 8px 10px; font-size: 13.5px; }
  .out-ok { color: var(--moss); font-size: 13px; margin-top: 8px; }
  .stat-row { display: flex; gap: 22px; flex-wrap: wrap; margin-top: 6px; }
  .stat { }
  .stat b { display: block; font-family: var(--font-display); font-size: 22px; }
  .stat span { font-size: 12px; color: var(--ink-faint); }
  .swatch { width: 100%; height: 64px; border-radius: var(--radius); border: 1px solid var(--border); margin-bottom: 12px; }
  .copy-btn { font-size: 12px; padding: 4px 9px; }
  mark.add { background: var(--moss-soft); color: var(--moss); text-decoration: none; }
  mark.del { background: var(--danger-soft); color: var(--danger); text-decoration: line-through; }

  .page-copy { margin-top: 40px; }
  .page-copy h2 { font-size: 19px; margin-top: 32px; }
  .page-copy p, .page-copy li { color: var(--ink-muted); font-size: 15px; }
  .faq dt { font-family: var(--font-display); font-weight: 600; font-size: 15px; color: var(--ink); margin-top: 16px; }
  .faq dd { margin: 6px 0 0; color: var(--ink-muted); font-size: 14.5px; }

  .hub-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 1px; background: var(--border); border: 1px solid var(--border); margin-top: 30px; }
  .hub-card { background: var(--bg-panel); padding: 18px; text-decoration: none; color: var(--ink); }
  .hub-card:hover { background: var(--bg-panel-raised); }
  .hub-card .cat { font-size: 11.5px; color: var(--moss); }
  .hub-card h3 { font-size: 16px; margin: 6px 0 4px; }
  .hub-card p { font-size: 13px; color: var(--ink-muted); margin: 0; }

  .hero { display: grid; grid-template-columns: 1.1fr 1fr; gap: 40px; align-items: start; margin-top: 6px; }
  @media (max-width: 860px) { .hero { grid-template-columns: 1fr; } }
  .hero h1 { font-size: clamp(30px, 4.4vw, 44px); }
  .hero-demo { background: var(--bg-panel); border: 1px solid var(--border); padding: 18px; position: relative; }

  footer { border-top: 1px solid var(--border); margin-top: 60px; padding: 30px 0 10px; }
  footer .cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 20px; }
  footer h4 { font-family: var(--font-display); font-size: 12.5px; color: var(--ink-faint); margin: 0 0 8px; }
  footer ul { list-style: none; margin: 0; padding: 0; }
  footer li a { color: var(--ink-muted); text-decoration: none; font-size: 13.5px; line-height: 2; }
  footer li a:hover { color: var(--ink); }
  .fine { color: var(--ink-faint); font-size: 12px; margin-top: 24px; }

  @media (max-width: 900px) {
    .shell { grid-template-columns: 1fr; }
    .side { position: fixed; left: -280px; top: 0; width: 260px; z-index: 20; transition: left .18s ease; box-shadow: 0 0 0 2000px rgba(0,0,0,0); }
    .side.open { left: 0; box-shadow: 4px 0 24px rgba(0,0,0,.25); }
    .topbar { display: flex; }
    .wrap { padding: 32px 20px 70px; }
  }