:root {
    --bg: #fbfaf7;
    --surface: #ffffff;
    --ink: #1c2420;
    --muted: #5d6b64;
    --line: #e4e7e1;
    --accent: #1f6f50;
    --accent-ink: #ffffff;
    --accent-soft: #e3f1ea;
    --debit: #1f6f50;
    --credit: #a8452f;
    --shadow: 0 1px 2px rgba(20, 30, 25, .06), 0 8px 24px rgba(20, 30, 25, .06);
  }
  @media (prefers-color-scheme: dark) {
    :root {
      --bg: #101613;
      --surface: #18201c;
      --ink: #eaf0ec;
      --muted: #9aaba2;
      --line: #28332d;
      --accent: #4cb98b;
      --accent-ink: #08140e;
      --accent-soft: #1b2d25;
      --debit: #4cb98b;
      --credit: #e0826c;
      --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .3);
    }
  }
  * { box-sizing: border-box; }
  html { scroll-behavior: smooth; }
  body {
    margin: 0;
    background: var(--bg);
    color: var(--ink);
    font: 17px/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    -webkit-font-smoothing: antialiased;
  }
  a { color: var(--accent); }
  .wrap { max-width: 1040px; margin: 0 auto; padding: 0 20px; }
  section { padding: 72px 0; }
  h1, h2, h3 { line-height: 1.2; margin: 0 0 .5em; letter-spacing: -.02em; }
  h1 { font-size: clamp(2.1rem, 5.5vw, 3.4rem); }
  h2 { font-size: clamp(1.6rem, 3.6vw, 2.2rem); }
  h3 { font-size: 1.1rem; letter-spacing: -.01em; }
  p { margin: 0 0 1em; }
  .lead { font-size: 1.2rem; color: var(--muted); max-width: 40em; }
  .eyebrow { color: var(--accent); font-weight: 650; font-size: .85rem; letter-spacing: .08em; text-transform: uppercase; margin-bottom: .8em; }

  /* header */
  header { padding: 18px 0; }
  header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; }
  .brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--ink); text-decoration: none; }
  .brand img { width: 28px; height: 28px; }
  nav { display: flex; gap: 22px; align-items: center; }
  nav a.plain { color: var(--muted); text-decoration: none; font-size: .95rem; }
  nav a.plain:hover { color: var(--ink); }

  .btn {
    display: inline-block; padding: 12px 22px; border-radius: 10px; font-weight: 650;
    text-decoration: none; background: var(--accent); color: var(--accent-ink);
    border: 1px solid var(--accent);
  }
  .btn:hover { filter: brightness(1.08); }
  .btn.ghost { background: transparent; color: var(--ink); border-color: var(--line); }
  .btn.ghost:hover { border-color: var(--muted); filter: none; }
  .btn.sm { padding: 8px 16px; font-size: .95rem; }
  .cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }
  .fine { color: var(--muted); font-size: .9rem; margin-top: 14px; }

  /* hero */
  .hero { padding-top: 40px; }
  .hero-grid { display: grid; grid-template-columns: 1.05fr .95fr; gap: 48px; align-items: center; }

  /* chat mock */
  .chat {
    background: var(--surface); border: 1px solid var(--line); border-radius: 18px;
    box-shadow: var(--shadow); padding: 18px; font-size: .95rem;
  }
  .msg { padding: 10px 14px; border-radius: 14px; margin-bottom: 10px; max-width: 92%; }
  .msg.you { background: var(--accent-soft); margin-left: auto; border-bottom-right-radius: 4px; }
  .msg.ai { background: var(--bg); border: 1px solid var(--line); border-bottom-left-radius: 4px; }
  .photo {
    display: flex; align-items: center; gap: 10px; font-size: .85rem; color: var(--muted);
  }
  .photo .thumb {
    width: 38px; height: 48px; border-radius: 4px; background:
      repeating-linear-gradient(0deg, var(--line) 0 2px, transparent 2px 6px), var(--surface);
    border: 1px solid var(--line);
  }
  .tool { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .8rem; color: var(--muted); margin: 2px 0 10px 4px; }
  .tool b { color: var(--accent); font-weight: 600; }
  table.post { width: 100%; border-collapse: collapse; font-size: .85rem; margin-top: 8px; }
  table.post th { text-align: left; color: var(--muted); font-weight: 600; padding: 4px 0; border-bottom: 1px solid var(--line); }
  table.post td { padding: 4px 0; border-bottom: 1px dashed var(--line); }
  table.post .n { text-align: right; font-variant-numeric: tabular-nums; }
  .dr { color: var(--debit); }
  .cr { color: var(--credit); }

  /* steps / cards */
  .grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 32px; }
  .grid2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; margin-top: 32px; }
  .card { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 24px; }
  .card p:last-child { margin-bottom: 0; }
  .card p { color: var(--muted); }
  .num {
    display: inline-flex; width: 32px; height: 32px; border-radius: 50%; align-items: center; justify-content: center;
    background: var(--accent-soft); color: var(--accent); font-weight: 700; margin-bottom: 12px;
  }
  .alt { background: var(--surface); border-block: 1px solid var(--line); }
  .alt .card { background: var(--bg); }

  /* double entry */
  .de { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: center; }
  .ledger { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 22px; box-shadow: var(--shadow); }
  .alt .ledger { background: var(--bg); }
  .ledger h3 { margin-bottom: .2em; }
  .ledger .sub { color: var(--muted); font-size: .9rem; margin-bottom: 12px; }
  .ledger .sum { margin-top: 10px; font-size: .9rem; color: var(--muted); }

  /* faq */
  details { border-bottom: 1px solid var(--line); padding: 16px 0; }
  summary { cursor: pointer; font-weight: 650; list-style: none; display: flex; justify-content: space-between; gap: 16px; }
  summary::-webkit-details-marker { display: none; }
  summary::after { content: "+"; color: var(--accent); font-size: 1.3rem; line-height: 1; }
  details[open] summary::after { content: "–"; }
  details p { color: var(--muted); margin: 12px 0 0; }

  .final { text-align: center; }
  .final .lead { margin-inline: auto; }
  .final .cta-row { justify-content: center; }

  footer { border-top: 1px solid var(--line); padding: 28px 0; color: var(--muted); font-size: .9rem; }
  footer .wrap { display: flex; flex-wrap: wrap; gap: 12px 24px; justify-content: space-between; }
  footer a { color: var(--muted); }

  .demo { margin: 24px 0 0; }
  .demo video { display: block; width: 100%; border: 1px solid var(--line); border-radius: 16px; background: var(--surface); }
  a:focus-visible, summary:focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }
  @media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

  @media (max-width: 820px) {
    section { padding: 52px 0; }
    .hero-grid, .de { grid-template-columns: 1fr; gap: 32px; }
    .grid3, .grid2 { grid-template-columns: 1fr; }
    nav a.plain { display: none; }
  }
  @media (max-width: 420px) {
    header .wrap { flex-wrap: wrap; }
    nav { width: 100%; justify-content: space-between; }
  }