:root {
    color-scheme: light dark;
    --canvas: #F3F5F8;
    --surface: #FFFFFF;
    --surface-soft: #E9EDF3;
    --ink: #14171C;
    --ink-soft: #3F4652;
    --muted: #687386;
    --line: #D7DDE6;
    --line-strong: #B9C2D0;
    --accent: #2867D3;
    --accent-deep: #174C9F;
    --accent-soft: #E8F0FF;
    --code-bg: #182232;
    --code-ink: #FFFFFF;
    --purpose-bg: #17202D;
    --purpose-ink: #F7F9FC;
    --purpose-muted: #CBD3DF;
    --focus: #0D55CE;
  }

  *, *::before, *::after { box-sizing: border-box; }
  html { background: var(--canvas); }
  body {
    margin: 0;
    min-block-size: 100vh;
    color: var(--ink);
    background: var(--canvas);
    font-family: 'Inter', system-ui, sans-serif;
    font-size: 1rem;
    line-height: 1.6;
  }
  a { color: var(--accent); text-decoration: none; }
  a:hover { text-decoration: underline; }
  a:focus-visible { outline: 3px solid var(--focus); outline-offset: 3px; }
  p { margin: 0; }
  h1, h2, h3 { margin: 0; color: var(--ink); }
  h1 { font-size: 2.75rem; line-height: 1.12; font-weight: 600; text-wrap: balance; }
  h2 { font-size: 1.125rem; line-height: 1.35; font-weight: 600; }
  h3 { font-size: 0.8125rem; line-height: 1.4; font-weight: 600; }

  .skip-link {
    position: fixed;
    inset: 12px auto auto 12px;
    z-index: 10;
    padding: 10px 14px;
    color: var(--surface);
    background: var(--ink);
    transform: translateY(-160%);
  }
  .skip-link:focus { transform: translateY(0); }

  .index-detail-page main,
  .index-detail-page footer,
  .index-list-page main,
  .index-list-page footer,
  .index-list-page .page-header {
    inline-size: min(100% - 48px, 1120px);
    margin-inline: auto;
  }

  .index-detail-page main { padding-block: 34px 72px; }
  .detail-article { min-inline-size: 0; }
  .breadcrumb { margin-block-end: 52px; font-size: 0.75rem; line-height: 1.45; }
  .breadcrumb ol {
    display: flex;
    flex-wrap: wrap;
    gap: 4px 8px;
    margin: 0;
    padding: 0;
    list-style: none;
  }
  .breadcrumb li:not(:last-child)::after { content: "›"; margin-inline-start: 8px; color: var(--muted); }

  .term-header { max-inline-size: 920px; padding-block-end: 52px; }
  .term-meta-row {
    display: flex;
    align-items: baseline;
    flex-wrap: wrap;
    gap: 10px 24px;
    margin-block-end: 18px;
  }
  .term-code { display: flex; align-items: baseline; gap: 10px; margin: 0; }
  .term-code-label { color: var(--accent-deep); font-size: 0.8125rem; font-weight: 600; letter-spacing: 0.08em; }
  .term-code-value {
    color: var(--accent-deep);
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.625rem;
    font-weight: 500;
    line-height: 1;
    letter-spacing: 0.02em;
  }
  .term-level { color: var(--muted); font-size: 0.875rem; }

  .content-layout {
    display: grid;
    grid-template-columns: minmax(0, 1.55fr) minmax(280px, 0.8fr);
    gap: 44px 64px;
    padding-block: 44px 52px;
    border-block: 1px solid var(--line);
  }
  .content-layout--single { grid-template-columns: minmax(0, 720px); }
  .content-primary { display: grid; align-content: start; gap: 40px; min-inline-size: 0; }
  .note-section h2,
  .related-section h2 { margin-block-end: 16px; }
  .note-section p { max-inline-size: 68ch; color: var(--ink-soft); font-size: 1.0625rem; text-wrap: pretty; }
  .note-list { display: block; max-inline-size: 68ch; margin: 0; }
  .note-list dt { display: inline; color: var(--ink); font-weight: 600; font-style: italic; }
  .note-list dd { display: inline; margin: 0; color: var(--ink-soft); font-style: italic; text-wrap: pretty; }
  .note-list dd::after { content: ""; display: block; block-size: 12px; }

  .purpose-section {
    align-self: start;
    padding: 28px;
    color: var(--purpose-ink);
    background: var(--purpose-bg);
    border-radius: 6px;
  }
  .purpose-section h2 { margin-block-end: 12px; color: var(--purpose-ink); }
  .purpose-section .summary { color: var(--purpose-muted); font-size: 0.9375rem; line-height: 1.7; text-wrap: pretty; }

  .taxonomy-section { padding-block: 52px 8px; }
  .taxonomy-heading {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 8px 24px;
    margin-block-end: 24px;
  }
  .taxonomy-heading h2 { font-size: 1.5rem; }
  .taxonomy-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(100%, 18rem), 1fr));
    gap: 36px 28px;
  }
  .index-nav-group { min-inline-size: 0; }
  .index-nav-group h3 { margin-block-end: 10px; color: var(--muted); }
  .index-nav-list { margin: 0; padding: 0; list-style: none; border-block-start: 1px solid var(--line-strong); }
  .index-nav-list li { border-block-end: 1px solid var(--line); }
  .index-nav-link {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    gap: 8px 14px;
    align-items: center;
    min-block-size: 66px;
    padding: 12px 10px;
    color: var(--ink);
    touch-action: manipulation;
    -webkit-tap-highlight-color: rgba(40,103,211,0.15);
    transition: background-color 140ms ease;
  }
  .index-nav-link:hover { color: var(--accent-deep); background: var(--accent-soft); text-decoration: none; }
  .index-nav-link:focus-visible { outline-offset: -3px; }
  .index-nav-code {
    grid-column: 1;
    justify-self: start;
    padding: 3px 7px;
    color: var(--code-ink);
    background: var(--code-bg);
    border-radius: 3px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 500;
    line-height: 1.35;
    letter-spacing: 0.01em;
    white-space: nowrap;
  }
  .index-nav-name { grid-column: 1; min-inline-size: 0; color: var(--accent); overflow-wrap: anywhere; }
  .index-nav-arrow { grid-column: 2; grid-row: 1 / span 2; color: var(--muted); font-size: 1.125rem; transition: transform 140ms ease; }
  .index-nav-link:hover .index-nav-arrow { color: var(--accent); transform: translateX(3px); }

  .source-note {
    display: grid;
    grid-template-columns: max-content minmax(0, 1fr);
    gap: 8px 18px;
    margin-block-start: 48px;
    padding-block-start: 20px;
    border-block-start: 1px solid var(--line);
    color: var(--muted);
    font-size: 0.8125rem;
  }
  .source-note strong,
  .source-note cite { color: var(--ink-soft); font-style: normal; }

  .index-detail-page footer { padding-block: 0 64px; }
  .page-actions { display: flex; flex-wrap: wrap; gap: 10px; }
  .page-action {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    min-block-size: 48px;
    padding: 10px 16px;
    color: var(--accent-deep);
    background: transparent;
    border: 1px solid var(--line-strong);
    border-radius: 4px;
    font-weight: 500;
    touch-action: manipulation;
  }
  .page-action:hover { background: var(--surface); border-color: var(--accent); text-decoration: none; }

  .index-list-page { padding-block: 48px 72px; }
  .index-list-page .page-header { display: flex; justify-content: space-between; gap: 20px; margin-block-end: 24px; }
  .index-list-page .page-title { font-size: 1.375rem; font-weight: 600; }
  .index-list-page .page-sub { color: var(--muted); font-size: 0.875rem; }
  .index-list-page .top-links { display: flex; flex-wrap: wrap; gap: 12px; }
  .index-list-page main { padding: 36px; background: var(--surface); border: 1px solid var(--line); }
  .index-list-page main h1 { font-size: 2rem; margin-block-end: 12px; }
  .index-list-page main > p { margin-block-end: 32px; color: var(--ink-soft); }
  .index-list-page main > section { padding-block: 24px; border-block-start: 1px solid var(--line); }
  .index-list-page main ul { margin: 0; padding-inline-start: 22px; }

  @media (prefers-color-scheme: dark) {
    :root {
      --canvas: #171A20;
      --surface: #22262E;
      --surface-soft: #2B303A;
      --ink: #EEF1F6;
      --ink-soft: #C4CAD4;
      --muted: #8F99A9;
      --line: #363D48;
      --line-strong: #4A5361;
      --accent: #78A7FF;
      --accent-deep: #A9C7FF;
      --accent-soft: #263B61;
      --code-bg: #DCE7FA;
      --code-ink: #172033;
      --purpose-bg: #E5EAF2;
      --purpose-ink: #151A22;
      --purpose-muted: #414B5B;
      --focus: #A9C7FF;
    }
  }

  @media (max-width: 800px) {
    h1 { font-size: 2.125rem; }
    .index-detail-page main,
    .index-detail-page footer,
    .index-list-page main,
    .index-list-page footer,
    .index-list-page .page-header { inline-size: min(100% - 32px, 1120px); }
    .breadcrumb { margin-block-end: 38px; }
    .term-header { padding-block-end: 40px; }
    .content-layout { grid-template-columns: 1fr; gap: 36px; padding-block: 36px 42px; }
    .content-primary { gap: 34px; }
    .purpose-section { max-inline-size: 44rem; }
    .taxonomy-section { padding-block-start: 42px; }
  }

  @media (max-width: 520px) {
    h1 { font-size: 1.75rem; }
    .index-detail-page main { padding-block: 24px 52px; }
    .breadcrumb { margin-block-end: 30px; }
    .term-meta-row { display: grid; gap: 12px; margin-block-end: 16px; }
    .term-code-value { font-size: 1.35rem; }
    .term-header { padding-block-end: 34px; }
    .content-layout { padding-block: 30px 36px; }
    .purpose-section { padding: 22px; }
    .taxonomy-heading h2 { font-size: 1.3rem; }
    .taxonomy-grid { gap: 30px; }
    .index-nav-link { min-block-size: 62px; }
    .source-note { grid-template-columns: 1fr; gap: 3px; margin-block-start: 38px; }
    .index-detail-page footer { padding-block-end: 44px; }
    .page-actions { display: grid; grid-template-columns: 1fr; }
    .page-action { justify-content: flex-start; }
    .index-list-page main { padding: 24px 20px; }
  }

  @media (pointer: coarse) {
    .index-nav-link { min-block-size: 70px; }
    .page-action { min-block-size: 54px; }
  }
  @media (prefers-reduced-motion: reduce) {
    .index-nav-link,
    .index-nav-arrow { transition: none; }
  }

  /* Production index pages: document-card system, ink-blue palette. */
  .index-detail-page {
    --canvas: #F3F3F0;
    --surface: #FFFFFF;
    --surface-soft: #E2E8EF;
    --ink: #18202A;
    --ink-soft: #37424E;
    --muted: #66717D;
    --line: #D2D8DF;
    --line-strong: #BBC5CE;
    --accent: #173F6B;
    --accent-deep: #173F6B;
    --accent-soft: #EDF2F6;
    --code-ink: #784552;
    --purpose-bg: #F7F8F8;
    --purpose-ink: #18202A;
    --purpose-muted: #37424E;
    --focus: #8B6C3F;
    color-scheme: light dark;
  }
  @media (prefers-color-scheme: dark) {
    .index-detail-page {
      --canvas: #191D23;
      --surface: #242932;
      --surface-soft: #2E3540;
      --ink: #EDF1F6;
      --ink-soft: #C8D0DB;
      --muted: #98A3B3;
      --line: #3A424F;
      --line-strong: #515B6A;
      --accent: #8EB8FF;
      --accent-deep: #8EB8FF;
      --accent-soft: #273A57;
      --code-ink: #F0B5C0;
      --purpose-bg: #202630;
      --purpose-ink: #EDF1F6;
      --purpose-muted: #C8D0DB;
      --focus: #D4B77C;
    }
  }
  .index-detail-page main,
  .index-detail-page footer { inline-size: min(100% - 40px, 1100px); }
  .index-detail-page main { padding-block: 38px 58px; }
  .index-detail-page .breadcrumb { margin-block-end: 22px; font-size: .78rem; line-height: 1.65; color: var(--muted); }
  .index-detail-page .record {
    overflow: hidden;
    background: var(--surface);
    border: 1px solid var(--line);
    box-shadow: 0 16px 50px rgba(25,43,64,.09);
  }
  .index-detail-page .term-header {
    display: grid;
    grid-template-columns: 260px minmax(0,1fr);
    max-inline-size: none;
    min-block-size: 240px;
    padding: 0;
    border-block-end: 1px solid var(--line);
  }
  .index-detail-page .term-meta-row {
    display: block;
    margin: 0;
    padding: 34px;
    background: var(--surface-soft);
  }
  .index-detail-page .term-code { display: block; margin: 0; }
  .index-detail-page .term-code-label {
    display: block;
    margin-block-end: 14px;
    color: var(--accent);
    font-size: .7rem;
    font-weight: 600;
    letter-spacing: .12em;
    text-transform: uppercase;
  }
  .index-detail-page .term-code-value {
    display: block;
    color: var(--ink);
    font-family: 'Courier New', monospace;
    font-size: 1.62rem;
    font-weight: 700;
    line-height: 1.25;
    letter-spacing: .045em;
    white-space: nowrap;
  }
  .index-detail-page .term-level { display: none; }
  .index-detail-page .term-header h1 {
    align-self: start;
    width: 100%;
    padding: 38px 44px;
    font-family: Georgia, 'Times New Roman', serif;
    font-size: var(--detail-title-size, 4.1rem);
    font-weight: 400;
    line-height: 1.08;
    text-wrap: balance;
  }
  .index-detail-page .content-layout {
    display: grid;
    grid-template-columns: minmax(0,1.2fr) minmax(280px,.8fr);
    gap: 0;
    padding: 0;
    border: 0;
    border-block-end: 1px solid var(--line);
  }
  .index-detail-page .content-layout--single { grid-template-columns: minmax(0, 1fr); }
  .index-detail-page .content-primary {
    display: grid;
    align-content: start;
    gap: 34px;
    padding: 42px 44px;
    border-inline-end: 1px solid var(--line);
  }
  .index-detail-page .note-section h2,
  .index-detail-page .related-section h2 { margin-block-end: 14px; }
  .index-detail-page h2,
  .index-detail-page h3 {
    color: var(--accent);
    font-family: 'Inter', system-ui, sans-serif;
    font-size: .78rem;
    font-weight: 600;
    letter-spacing: .1em;
    text-transform: uppercase;
  }
  .index-detail-page .note-section p,
  .index-detail-page .note-list {
    max-inline-size: 68ch;
    color: var(--ink);
    font-family: Georgia, 'Times New Roman', serif;
    font-size: 1.1rem;
    line-height: 1.7;
  }
  .index-detail-page .note-list dt { color: var(--ink); }
  .index-detail-page .note-list dd { color: var(--ink-soft); }
  .index-detail-page .purpose-section {
    align-self: stretch;
    padding: 42px 36px;
    color: var(--purpose-ink);
    background: var(--purpose-bg);
    border: 0;
    border-radius: 0;
  }
  .index-detail-page .purpose-section h2 { margin-block-end: 14px; color: var(--focus); }
  .index-detail-page .purpose-section .summary { color: var(--purpose-muted); font-size: 1.05rem; line-height: 1.7; }
  .index-detail-page .taxonomy-section { padding: 42px 44px; border-block-start: 0; }
  .index-detail-page .taxonomy-heading { margin-block-end: 28px; }
  .index-detail-page .taxonomy-heading h2 {
    color: var(--ink);
    font-family: Georgia, 'Times New Roman', serif;
    font-size: 1.6rem;
    font-weight: 400;
    letter-spacing: 0;
    text-transform: none;
  }
  .index-detail-page .taxonomy-grid { grid-template-columns: repeat(3,minmax(0,1fr)); gap: 24px; }
  .index-detail-page .index-nav-group { border: 1px solid var(--line); background: var(--surface); }
  .index-detail-page .index-nav-group h3 {
    margin: 0;
    padding: 12px 14px;
    background: var(--surface-soft);
  }
  .index-detail-page .index-nav-list { border-block-start: 0; }
  .index-detail-page .index-nav-link {
    display: grid;
    grid-template-columns: minmax(0,1fr) auto;
    gap: 3px 12px;
    min-block-size: 68px;
    padding: 12px 14px;
    color: var(--accent);
  }
  .index-detail-page .index-nav-code {
    display: block;
    justify-self: start;
    padding: 0;
    color: var(--code-ink);
    background: transparent;
    border-radius: 0;
    font-family: 'Courier New', monospace;
    font-size: 14px;
    font-weight: 700;
    line-height: 1.35;
    letter-spacing: .025em;
  }
  .index-detail-page .index-nav-name { color: var(--accent); line-height: 1.5; }
  .index-detail-page .index-nav-arrow { color: var(--accent); }
  .index-detail-page .related-section .index-nav-list { border-block-start: 1px solid var(--line); }
  .index-detail-page .related-section .index-nav-link {
    grid-template-columns: 116px minmax(0,1fr) auto;
    column-gap: 14px;
    min-block-size: 58px;
    padding-inline: 0;
  }
  .index-detail-page .related-section .index-nav-code,
  .index-detail-page .related-section .index-nav-name { grid-row: 1; }
  .index-detail-page .related-section .index-nav-name { grid-column: 2; }
  .index-detail-page .related-section .index-nav-arrow { grid-column: 3; grid-row: 1; }
  .index-detail-page .source-note {
    margin: 0 44px;
    padding-block: 18px 24px;
    border-block-start: 1px solid var(--line);
  }
  .index-detail-page footer { padding-block: 22px 64px; }
  .index-detail-page .page-action { border-radius: 0; }

  @media (max-width: 800px) {
    .index-detail-page main,
    .index-detail-page footer { inline-size: min(100% - 24px,1100px); }
    .index-detail-page .term-header { grid-template-columns: 1fr; }
    .index-detail-page .term-meta-row { padding: 24px; }
    .index-detail-page .term-header h1 { padding: 28px 24px; font-size: min(var(--detail-title-size,2.6rem),2.6rem); }
    .index-detail-page .content-layout { grid-template-columns: 1fr; }
    .index-detail-page .content-primary { padding: 30px 24px; border-inline-end: 0; border-block-end: 1px solid var(--line); }
    .index-detail-page .purpose-section { padding: 30px 24px; }
    .index-detail-page .taxonomy-section { padding: 32px 24px; }
    .index-detail-page .taxonomy-grid { grid-template-columns: 1fr; }
    .index-detail-page .source-note { margin-inline: 24px; }
  }

  @media (max-width: 520px) {
    .index-detail-page main { padding-block: 24px 42px; }
    .index-detail-page .term-code-value { font-size: 1.4rem; }
    .index-detail-page .term-header h1 { font-size: min(var(--detail-title-size,2.3rem),2.3rem); }
    .index-detail-page .related-section .index-nav-link { grid-template-columns: 1fr auto; gap: 3px 10px; }
    .index-detail-page .related-section .index-nav-code { grid-column: 1; }
    .index-detail-page .related-section .index-nav-name { grid-column: 1; grid-row: 2; }
    .index-detail-page .related-section .index-nav-arrow { grid-column: 2; grid-row: 1 / span 2; }
  }