:root {
    --bg: #eef1f4;
    --surface: #ffffff;
    --surface-2: #e8ecef;
    --border: #d5dade;
    --text: #12191f;
    --text-muted: #5b6670;
    --accent: #f28c00;
    --accent-strong: #c26800;
    --accent-soft: #fdecd2;
    --success: #2f8f4e;
    --success-soft: #e1f3e6;
    --warning: #a3701c;
    --warning-soft: #fbedd6;
    --danger: #b23434;
    --danger-soft: #fbe3e3;
    --ib: #3563a0;
    --ib-soft: #e4ecf5;
    --iz: #1f8a72;
    --iz-soft: #e0f2ed;
    --shadow: 0 1px 2px rgba(20,24,29,0.06), 0 8px 24px rgba(20,24,29,0.06);
  }


  @media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
      --bg: #0e1417;
      --surface: #161e23;
      --surface-2: #1c262c;
      --border: #303b42;
      --text: #edeeee;
      --text-muted: #98a4ac;
      --accent: #ffa733;
      --accent-strong: #ffc06a;
      --accent-soft: #3a2a12;
      --success: #4fbb72;
      --success-soft: #163826;
      --warning: #d9a441;
      --warning-soft: #3a2e14;
      --danger: #e1615f;
      --danger-soft: #3a1d1d;
      --ib: #7aa8db;
      --ib-soft: #1c2836;
      --iz: #52c9ab;
      --iz-soft: #123028;
      --shadow: 0 1px 2px rgba(0,0,0,0.3), 0 8px 24px rgba(0,0,0,0.35);
    }
  }
  :root[data-theme="dark"] {
    --bg: #0e1417;
    --surface: #161e23;
    --surface-2: #1c262c;
    --border: #303b42;
    --text: #edeeee;
    --text-muted: #98a4ac;
    --accent: #ffa733;
    --accent-strong: #ffc06a;
    --accent-soft: #3a2a12;
    --success: #4fbb72;
    --success-soft: #163826;
    --warning: #d9a441;
    --warning-soft: #3a2e14;
    --danger: #e1615f;
    --danger-soft: #3a1d1d;
    --ib: #7aa8db;
    --ib-soft: #1c2836;
    --iz: #52c9ab;
    --iz-soft: #123028;
    --shadow: 0 1px 2px rgba(0,0,0,0.3), 0 8px 24px rgba(0,0,0,0.35);
  }

  * { box-sizing: border-box; }
  html, body { margin: 0; padding: 0; }
  body {
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
  }
  .num { font-family: "IBM Plex Mono", ui-monospace, monospace; font-variant-numeric: tabular-nums; }

  .wrap {
    max-width: 960px;
    margin: 0 auto;
    padding: 2rem 1.25rem 4rem;
    font-family: "IBM Plex Sans", ui-sans-serif, system-ui, sans-serif;
    color: var(--text);
    line-height: 1.5;
  }

  .wrap header.page { margin-bottom: 1.5rem; }
  .wrap .hero-card { margin-bottom: 1.1rem; }
  .wrap .eyebrow {
    font-family: "Oswald", ui-sans-serif, sans-serif;
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--accent-strong);
    background: var(--surface);
    border: 1px solid color-mix(in srgb, var(--accent) 32%, var(--border));
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.32rem 0.75rem 0.32rem 0.55rem;
    border-radius: 999px;
    margin-top: 0.75rem;
  }
  .eyebrow-icon { width: 15px; height: 15px; flex-shrink: 0; }
  .eyebrow-icon svg { width: 100%; height: 100%; display: block; }
  h1 {
    font-family: "Oswald", ui-sans-serif, sans-serif;
    font-weight: 600;
    font-size: clamp(1.7rem, 3.4vw, 2.35rem);
    letter-spacing: -0.01em;
    text-wrap: balance;
    margin: 0 0 0.55rem;
    background: linear-gradient(90deg, var(--text) 55%, var(--accent-strong) 130%);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
  }
  .lede { color: var(--text-muted); font-size: 1.02rem; max-width: 62ch; margin: 0; }

  .callout {
    margin-top: 1.2rem;
    background: var(--accent-soft);
    border: 1px solid color-mix(in srgb, var(--accent) 35%, var(--border));
    border-radius: 12px;
    padding: 0.85rem 1.05rem;
    font-size: 0.9rem;
    color: var(--text);
    box-shadow: var(--shadow);
  }
  .callout-row { display: flex; align-items: flex-start; gap: 0.7rem; }
  .callout-icon {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background: var(--accent);
    color: #ffffff;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    margin-top: 0.05rem;
  }
  .callout-icon svg { width: 17px; height: 17px; }
  .callout b { color: var(--accent-strong); }
  .callout-text { flex: 1; min-width: 0; }

  .toolbar { display: flex; align-items: center; gap: 0.7rem; margin-top: 1.2rem; flex-wrap: wrap; }
  .btn {
    font-family: "IBM Plex Sans", sans-serif;
    font-size: 0.84rem;
    font-weight: 600;
    padding: 0.6rem 1.15rem;
    border-radius: 9px;
    cursor: pointer;
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--text);
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    box-shadow: 0 1px 2px rgba(20,24,29,0.05);
    transition: border-color .15s ease, background .15s ease, color .15s ease, box-shadow .15s ease, transform .1s ease;
  }
  .btn svg { width: 16px; height: 16px; flex-shrink: 0; }
  .btn:hover { border-color: var(--accent); box-shadow: 0 2px 6px rgba(20,24,29,0.09); transform: translateY(-1px); }
  .btn:active { transform: translateY(0); }
  .btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
  .btn-primary { background: var(--accent); border-color: var(--accent); color: #ffffff; box-shadow: 0 2px 8px color-mix(in srgb, var(--accent) 35%, transparent); }
  .btn-primary:hover { background: var(--accent-strong); border-color: var(--accent-strong); box-shadow: 0 3px 10px color-mix(in srgb, var(--accent) 45%, transparent); }
  .share-feedback { font-size: 0.78rem; color: var(--success); font-weight: 600; opacity: 0; transition: opacity .25s ease; }
  .share-feedback.show { opacity: 1; }

  .grid { display: grid; grid-template-columns: minmax(0, 1fr); gap: 1.1rem; margin-top: 1.5rem; }
  @media (min-width: 860px) { .grid { grid-template-columns: 380px minmax(0, 1fr); align-items: start; } }

  .card { background: var(--surface); border: 1px solid var(--border); border-radius: 14px; padding: 1.15rem 1.25rem 1.3rem; box-shadow: var(--shadow); }
  .card + .card { margin-top: 1.1rem; }
  .card h2 {
    font-family: "Oswald", ui-sans-serif, sans-serif;
    font-size: 0.95rem;
    font-weight: 600;
    letter-spacing: 0.02em;
    margin: 0 0 0.85rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
  }
  .card h2 .idx {
    font-size: 0.7rem;
    color: var(--text-muted);
    font-weight: 500;
    background: var(--surface-2);
    border: 1px solid var(--border);
    border-radius: 5px;
    padding: 0.1rem 0.4rem;
    font-family: "IBM Plex Mono", monospace;
  }

  fieldset { border: none; padding: 0; margin: 0 0 1rem; }
  legend { font-size: 0.82rem; font-weight: 600; color: var(--text); padding: 0 0 0.5rem; width: 100%; }
  .radio-row { display: flex; flex-direction: column; gap: 0.45rem; }
  .radio-opt {
    display: flex; align-items: flex-start; gap: 0.55rem;
    border: 1px solid var(--border); border-radius: 9px; padding: 0.55rem 0.7rem;
    cursor: pointer; transition: border-color .15s ease, background .15s ease;
  }
  .radio-opt:hover { border-color: var(--accent); }
  .radio-opt.active { border-color: var(--accent); background: var(--accent-soft); }
  .radio-opt input { margin-top: 0.2rem; accent-color: var(--accent); flex-shrink: 0; }
  .radio-opt .lbl { font-size: 0.88rem; font-weight: 500; }
  .radio-opt .sub { font-size: 0.78rem; color: var(--text-muted); display: block; margin-top: 0.1rem; }
  .tag-rec {
    font-size: 0.62rem; font-weight: 600; letter-spacing: 0.04em; text-transform: uppercase;
    color: var(--success); background: var(--success-soft); border-radius: 4px; padding: 0.08rem 0.35rem; margin-left: 0.4rem;
  }

  label.field-label { display: block; font-size: 0.8rem; font-weight: 500; color: var(--text-muted); margin: 0 0 0.35rem; }
  .field-group { margin-bottom: 1rem; }
  .field-group:last-child { margin-bottom: 0; }
  input[type="number"], select {
    width: 100%; background: var(--surface-2); border: 1px solid var(--border); color: var(--text);
    border-radius: 8px; padding: 0.55rem 0.65rem; font-size: 0.92rem; font-family: "IBM Plex Mono", monospace;
  }
  select { font-family: "IBM Plex Sans", sans-serif; }
  input[type="number"]:focus, select:focus, input[type="radio"]:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
  .conditional-input { margin-top: 0.6rem; padding-left: 1.75rem; }
  .inline-fields { display: flex; gap: 0.6rem; }
  .inline-fields > div { flex: 1; }

  details.adv { border-top: 1px dashed var(--border); padding-top: 0.85rem; margin-top: 0.3rem; }
  details.adv summary { cursor: pointer; font-size: 0.82rem; font-weight: 600; color: var(--accent-strong); list-style: none; }
  details.adv summary::-webkit-details-marker { display: none; }
  details.adv summary::before { content: "\25b8 "; display: inline-block; }
  details.adv[open] summary::before { content: "\25be "; }
  details.adv .adv-body { margin-top: 0.85rem; }
  .adv-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.8rem; }

  .result-tiles { display: grid; grid-template-columns: 1fr 1fr; gap: 0.85rem; }
  @media (max-width: 520px) { .result-tiles { grid-template-columns: 1fr; } }
  .tile { background: var(--surface-2); border: 1px solid var(--border); border-radius: 12px; padding: 0.95rem 1rem; position: relative; overflow: hidden; }
  .tile::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px; background: var(--accent); }
  .tile .tile-label { font-family: "Oswald", sans-serif; font-size: 0.7rem; font-weight: 600; letter-spacing: 0.1em; text-transform: uppercase; color: var(--text-muted); margin-bottom: 0.4rem; }
  .tile .tile-value { font-family: "IBM Plex Mono", monospace; font-size: 1.6rem; font-weight: 600; line-height: 1.1; color: var(--text); }
  .tile .tile-value small { font-size: 0.92rem; font-weight: 500; color: var(--text-muted); }
  .chip-row { margin-top: 0.5rem; display: flex; gap: 0.4rem; flex-wrap: wrap; }
  .chip { font-size: 0.66rem; font-weight: 600; padding: 0.18rem 0.5rem; border-radius: 999px; letter-spacing: 0.02em; }
  .chip.accent { background: var(--accent-soft); color: var(--accent-strong); }
  .chip.bad { background: var(--danger-soft); color: var(--danger); }

  .stat-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.65rem; margin-top: 0.85rem; }
  @media (max-width: 620px) { .stat-row { grid-template-columns: 1fr 1fr; } }
  .stat { border: 1px solid var(--border); border-radius: 10px; padding: 0.6rem 0.7rem; }
  .stat .k { font-size: 0.68rem; color: var(--text-muted); margin-bottom: 0.25rem; }
  .stat .v { font-family: "IBM Plex Mono", monospace; font-size: 1rem; font-weight: 600; }
  .stat .v.small-note { font-size: 0.7rem; font-weight: 500; color: var(--text-muted); margin-top: 0.15rem; }

  .formula-band { margin-top: 1rem; }
  .formula-row { display: flex; align-items: stretch; gap: 0.55rem; }
  @media (max-width: 620px) {
    .formula-row { flex-direction: column; }
    .formula-op { padding: 0.05rem 0; }
  }
  .formula-term {
    flex: 1;
    min-width: 0;
    border-radius: 12px;
    padding: 0.8rem 0.65rem;
    text-align: center;
    border: 1.5px solid;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.2rem;
  }
  .formula-term.ib { background: var(--ib-soft); border-color: var(--ib); }
  .formula-term.in { background: var(--accent-soft); border-color: var(--accent); }
  .formula-term.iz { background: var(--iz-soft); border-color: var(--iz); }
  .ft-icon { width: 26px; height: 26px; margin-bottom: 0.1rem; }
  .ft-icon svg { width: 100%; height: 100%; }
  .formula-term.ib .ft-icon, .formula-term.ib .ft-var { color: var(--ib); }
  .formula-term.in .ft-icon, .formula-term.in .ft-var { color: var(--accent-strong); }
  .formula-term.iz .ft-icon, .formula-term.iz .ft-var { color: var(--iz); }
  .ft-var { font-family: "Oswald", sans-serif; font-size: 1.02rem; font-weight: 600; }
  .ft-label { font-size: 0.66rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.03em; }
  .ft-value { font-family: "IBM Plex Mono", monospace; font-size: 1.15rem; font-weight: 700; color: var(--text); }
  .formula-op {
    display: flex; align-items: center; justify-content: center;
    font-size: 1.3rem; font-weight: 700; width: 1.5rem; flex-shrink: 0;
  }
  .formula-op.ok { color: var(--success); }
  .formula-op.bad { color: var(--danger); }
  .formula-verdict {
    margin-top: 0.7rem; display: flex; align-items: center; gap: 0.55rem;
    padding: 0.6rem 0.8rem; border-radius: 10px; font-size: 0.85rem; font-weight: 600;
  }
  .formula-verdict.ok { background: var(--success-soft); color: var(--success); }
  .formula-verdict.bad { background: var(--danger-soft); color: var(--danger); }
  .fv-icon { font-size: 1.05rem; flex-shrink: 0; }

  .placeholder { color: var(--text-muted); font-size: 0.9rem; padding: 1.4rem 0; text-align: center; border: 1px dashed var(--border); border-radius: 10px; }

  details.steps-detail { margin-top: 0.9rem; border-top: 1px dashed var(--border); padding-top: 0.75rem; }
  details.steps-detail summary { cursor: pointer; font-size: 0.85rem; font-weight: 600; color: var(--accent-strong); list-style: none; }
  details.steps-detail summary::-webkit-details-marker { display: none; }
  details.steps-detail summary::before { content: "\25b8 "; }
  details.steps-detail[open] summary::before { content: "\25be "; }
  .steps { margin-top: 0.8rem; font-size: 0.85rem; }
  .steps ol { margin: 0.4rem 0 0; padding-left: 1.2rem; }
  .steps li { margin-bottom: 0.5rem; }
  .steps .formula {
    display: block; font-family: "IBM Plex Mono", monospace; background: var(--surface-2);
    border: 1px solid var(--border); border-radius: 6px; padding: 0.35rem 0.55rem; margin-top: 0.25rem; font-size: 0.8rem; overflow-x: auto;
  }

  table.ref { width: 100%; border-collapse: collapse; font-size: 0.84rem; margin-top: 0.5rem; }
  table.ref th, table.ref td { text-align: left; padding: 0.4rem 0.5rem; border-bottom: 1px solid var(--border); }
  table.ref th { font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.04em; color: var(--text-muted); font-weight: 600; }
  table.ref td.num { font-family: "IBM Plex Mono", monospace; }
  .table-wrap { overflow-x: auto; }
  .table-caption { margin-top: 0.55rem; font-size: 0.78rem; color: var(--text-muted); }

  .notes { margin-top: 1rem; font-size: 0.82rem; color: var(--text-muted); }
  .notes ul { margin: 0.4rem 0 0; padding-left: 1.1rem; }
  .notes li { margin-bottom: 0.3rem; }

  .calc-page-footer, footer.page { margin-top: 1.75rem; font-size: 0.75rem; color: var(--text-muted); border-top: 1px solid var(--border); padding-top: 0.9rem; }
  .ad-slot { margin-top: 1rem; min-height: 0; overflow: hidden; }