@layer reset, base, theme, layout, components, utilities;

@layer reset {
  html {
    box-sizing: border-box;
    -webkit-text-size-adjust: 100%;
    scroll-padding-top: 9rem;
  }

  *, *::before, *::after {
    box-sizing: inherit;
  }

  body, h1, h2, h3, h4, p, figure, blockquote, dl, dd {
    margin: 0;
  }

  ul[role="list"], ol[role="list"] {
    list-style: none;
    margin: 0;
    padding: 0;
  }

  button, input, select, textarea {
    font: inherit;
    color: inherit;
  }

  img, svg {
    display: block;
    max-inline-size: 100%;
  }
}

@layer theme {
  :root {
    color-scheme: light dark;

    /* Tier 1: Palette tokens */
    --bg-light: #f4f6f8;
    --bg-dark: #0f1419;
    --surface-light: #ffffff;
    --surface-dark: #171e26;
    --surface-alt-light: #eaeff4;
    --surface-alt-dark: #1f2833;
    --text-light: #161d24;
    --text-dark: #edf2f7;
    --muted-light: #4b5866;
    --muted-dark: #9fb0c2;
    --border-light: #cbd5e1;
    --border-dark: #2e3b4a;

    --accent-light: #0369a1;
    --accent-dark: #38bdf8;
    --accent-contrast-light: #ffffff;
    --accent-contrast-dark: #082032;
    --accent-subtle-light: #e0f2fe;
    --accent-subtle-dark: #0c2d48;

    --ok-light: #15803d;
    --ok-dark: #4ade80;
    --ok-bg-light: #dcfce7;
    --ok-bg-dark: #0d2e1b;

    --warn-light: #b45309;
    --warn-dark: #fbbf24;
    --warn-bg-light: #fef3c7;
    --warn-bg-dark: #332208;

    --danger-light: #b91c1c;
    --danger-dark: #f87171;
    --danger-bg-light: #fee2e2;
    --danger-bg-dark: #361215;

    --focus-light: #c2410c;
    --focus-dark: #fb923c;

    /* Tier 2: Semantic tokens (default light, fallback for pre-light-dark browsers) */
    --bg: var(--bg-light);
    --surface: var(--surface-light);
    --surface-alt: var(--surface-alt-light);
    --text: var(--text-light);
    --muted: var(--muted-light);
    --border: var(--border-light);
    --accent: var(--accent-light);
    --accent-contrast: var(--accent-contrast-light);
    --accent-subtle: var(--accent-subtle-light);
    --ok: var(--ok-light);
    --ok-bg: var(--ok-bg-light);
    --warn: var(--warn-light);
    --warn-bg: var(--warn-bg-light);
    --danger: var(--danger-light);
    --danger-bg: var(--danger-bg-light);
    --focus-ring: var(--focus-light);

    --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --font-mono: ui-monospace, "SFMono-Regular", Menlo, Monaco, Consolas, monospace;

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --shadow-sm: 0 1px 2px rgb(0 0 0 / 0.06);
    --shadow-md: 0 6px 20px rgb(0 0 0 / 0.08);
    --max-width: 1240px;
  }

  @media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
      --bg: var(--bg-dark);
      --surface: var(--surface-dark);
      --surface-alt: var(--surface-alt-dark);
      --text: var(--text-dark);
      --muted: var(--muted-dark);
      --border: var(--border-dark);
      --accent: var(--accent-dark);
      --accent-contrast: var(--accent-contrast-dark);
      --accent-subtle: var(--accent-subtle-dark);
      --ok: var(--ok-dark);
      --ok-bg: var(--ok-bg-dark);
      --warn: var(--warn-dark);
      --warn-bg: var(--warn-bg-dark);
      --danger: var(--danger-dark);
      --danger-bg: var(--danger-bg-dark);
      --focus-ring: var(--focus-dark);
    }
  }

  :root[data-theme="light"] {
    color-scheme: light;
  }

  :root[data-theme="dark"] {
    color-scheme: dark;
    --bg: var(--bg-dark);
    --surface: var(--surface-dark);
    --surface-alt: var(--surface-alt-dark);
    --text: var(--text-dark);
    --muted: var(--muted-dark);
    --border: var(--border-dark);
    --accent: var(--accent-dark);
    --accent-contrast: var(--accent-contrast-dark);
    --accent-subtle: var(--accent-subtle-dark);
    --ok: var(--ok-dark);
    --ok-bg: var(--ok-bg-dark);
    --warn: var(--warn-dark);
    --warn-bg: var(--warn-bg-dark);
    --danger: var(--danger-dark);
    --danger-bg: var(--danger-bg-dark);
    --focus-ring: var(--focus-dark);
  }

  @supports (color: light-dark(white, black)) {
    :root {
      --bg: light-dark(var(--bg-light), var(--bg-dark));
      --surface: light-dark(var(--surface-light), var(--surface-dark));
      --surface-alt: light-dark(var(--surface-alt-light), var(--surface-alt-dark));
      --text: light-dark(var(--text-light), var(--text-dark));
      --muted: light-dark(var(--muted-light), var(--muted-dark));
      --border: light-dark(var(--border-light), var(--border-dark));
      --accent: light-dark(var(--accent-light), var(--accent-dark));
      --accent-contrast: light-dark(var(--accent-contrast-light), var(--accent-contrast-dark));
      --accent-subtle: light-dark(var(--accent-subtle-light), var(--accent-subtle-dark));
      --ok: light-dark(var(--ok-light), var(--ok-dark));
      --ok-bg: light-dark(var(--ok-bg-light), var(--ok-bg-dark));
      --warn: light-dark(var(--warn-light), var(--warn-dark));
      --warn-bg: light-dark(var(--warn-bg-light), var(--warn-bg-dark));
      --danger: light-dark(var(--danger-light), var(--danger-dark));
      --danger-bg: light-dark(var(--danger-bg-light), var(--danger-bg-dark));
      --focus-ring: light-dark(var(--focus-light), var(--focus-dark));
    }
  }

  html {
    accent-color: var(--accent);
  }

  @media (forced-colors: active) {
    :root {
      --border: CanvasText;
      --accent: Highlight;
      --focus-ring: Highlight;
    }
  }
}

@layer base {
  body {
    font-family: var(--font-sans);
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.55;
    text-align: start;
    min-block-size: 100dvh;
    display: flex;
    flex-direction: column;
  }

  h1, h2, h3, h4 {
    line-height: 1.25;
    text-wrap: balance;
  }

  h1 {
    font-size: clamp(1.5rem, 1.15rem + 1.4vw, 2.2rem);
    letter-spacing: -0.02em;
  }

  h2 {
    font-size: clamp(1.15rem, 1.05rem + 0.5vw, 1.45rem);
  }

  h3 {
    font-size: 1.05rem;
  }

  p, li {
    text-wrap: pretty;
    max-inline-size: 75ch;
  }

  a {
    color: var(--accent);
    text-underline-offset: 0.18em;
  }

  code, kbd {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 0.1em 0.35em;
  }

  :where(a:any-link, button, summary, input, select):focus-visible {
    outline: 3px solid var(--focus-ring);
    outline-offset: 2px;
  }
}

@layer layout {
  .site-header {
    background: var(--surface);
    border-block-end: 1px solid var(--border);
    position: sticky;
    inset-block-start: 0;
    z-index: 20;
  }

  @media (max-width: 760px) {
    .site-header {
      position: static;
    }
  }

  .header-inner,
  .safety-ribbon-inner,
  main,
  .footer-inner {
    inline-size: 100%;
    max-inline-size: var(--max-width);
    margin-inline: auto;
    padding-inline: clamp(1rem, 3vw, 1.75rem);
  }

  .header-inner {
    padding-block: 0.75rem;
    display: grid;
    gap: 0.75rem;
  }

  .brand-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 0.75rem;
  }

  .nav-search-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 0.75rem;
  }

  main {
    flex: 1;
    padding-block: 1.5rem 3rem;
  }

  .site-footer {
    background: var(--surface);
    border-block-start: 1px solid var(--border);
    padding-block: 1.25rem;
    font-size: 0.9rem;
  }

  .footer-inner {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: 0.5rem 1.5rem;
  }
}

@layer components {
  .skip-link {
    position: absolute;
    inset-inline-start: -9999px;
    inset-block-start: 0.5rem;
    z-index: 100;
    background: var(--accent);
    color: var(--accent-contrast);
    padding: 0.6rem 1rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    text-decoration: none;
  }

  .skip-link:focus {
    inset-inline-start: 0.5rem;
  }

  .brand {
    display: inline-flex;
    align-items: center;
    gap: 0.65rem;
    text-decoration: none;
    color: var(--text);
  }

  .brand-icon {
    color: var(--accent);
    flex-shrink: 0;
  }

  .brand-text {
    display: flex;
    flex-direction: column;
    line-height: 1.15;
  }

  .brand-text strong {
    font-size: 1.1rem;
  }

  .brand-sub {
    font-size: 0.78rem;
    color: var(--muted);
  }

  .header-controls {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
  }

  /* Experience level segmented switcher */
  .skill-switcher {
    display: inline-flex;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-alt);
    padding: 2px;
    margin: 0;
  }

  .skill-option {
    position: relative;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
  }

  .skill-option input {
    position: absolute;
    opacity: 0;
    inline-size: 1px;
    block-size: 1px;
  }

  .skill-option span {
    padding: 0.32rem 0.7rem;
    min-block-size: 34px;
    display: inline-flex;
    align-items: center;
    border-radius: 4px;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--muted);
    transition: background-color 0.15s ease, color 0.15s ease;
  }

  .skill-option:has(:checked) span {
    background: var(--surface);
    color: var(--text);
    box-shadow: var(--shadow-sm);
  }

  .skill-option:has(:focus-visible) span {
    outline: 2px solid var(--focus-ring);
    outline-offset: 1px;
  }

  .icon-btn,
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.4rem;
    min-block-size: 40px;
    padding: 0.45rem 0.9rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--text);
    font-weight: 600;
    font-size: 0.88rem;
    cursor: pointer;
    text-decoration: none;
  }

  .icon-btn:hover:not(:disabled),
  .btn:hover:not(:disabled) {
    background: var(--surface-alt);
  }

  .btn-primary {
    background: var(--accent);
    color: var(--accent-contrast);
    border-color: var(--accent);
  }

  .btn-primary:hover:not(:disabled) {
    filter: brightness(1.08);
    background: var(--accent);
  }

  /* Primary navigation */
  .primary-nav ul {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem;
  }

  .primary-nav a {
    display: inline-flex;
    align-items: center;
    min-block-size: 40px;
    padding: 0.4rem 0.8rem;
    border-radius: var(--radius-sm);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--muted);
    border: 1px solid transparent;
  }

  .primary-nav a:hover {
    color: var(--text);
    background: var(--surface-alt);
  }

  .primary-nav a[aria-current="page"] {
    background: var(--accent-subtle);
    color: var(--accent);
    border-color: var(--border);
  }

  /* Search */
  .global-search form {
    position: relative;
    display: flex;
    align-items: center;
  }

  .global-search input {
    min-block-size: 40px;
    inline-size: min(100%, 280px);
    padding: 0.4rem 2.1rem 0.4rem 0.75rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-alt);
    font-size: 0.9rem;
  }

  .kbd-hint {
    position: absolute;
    inset-inline-end: 0.5rem;
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--muted);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 0.05rem 0.35rem;
    pointer-events: none;
  }

  /* Safety ribbon */
  .safety-ribbon {
    background: var(--warn-bg);
    border-block-end: 1px solid var(--border);
    padding-block: 0.5rem;
    font-size: 0.88rem;
  }

  .safety-ribbon-inner {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.5rem 0.85rem;
  }

  .safety-ribbon p {
    max-inline-size: none;
  }

  /* Badges */
  .badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.15rem 0.55rem;
    border-radius: 999px;
    font-size: 0.78rem;
    font-weight: 700;
    border: 1px solid transparent;
    white-space: nowrap;
  }

  .badge-ok { background: var(--ok-bg); color: var(--ok); border-color: var(--ok); }
  .badge-warn { background: var(--warn-bg); color: var(--warn); border-color: var(--warn); }
  .badge-danger { background: var(--danger-bg); color: var(--danger); border-color: var(--danger); }
  .badge-info { background: var(--accent-subtle); color: var(--accent); border-color: var(--accent); }
  .badge-neutral { background: var(--surface-alt); color: var(--muted); border-color: var(--border); }

  .eyebrow {
    font-size: 0.78rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--accent);
    margin-block-end: 0.25rem;
  }

  .lead {
    color: var(--muted);
    font-size: 1.02rem;
    margin-block-start: 0.4rem;
  }

  .muted {
    color: var(--muted);
  }

  .section-header {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-end;
    justify-content: space-between;
    gap: 1rem;
    margin-block-end: 1.25rem;
  }

  /* Hero & Golden Rules */
  .hero-panel {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: clamp(1.1rem, 2.5vw, 1.75rem);
    margin-block-end: 1.5rem;
    display: grid;
    gap: 1.25rem;
    box-shadow: var(--shadow-sm);
  }

  .hero-quick-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 0.85rem;
  }

  .rule-card {
    display: flex;
    gap: 0.75rem;
    align-items: flex-start;
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 0.85rem;
  }

  .rule-num {
    font-family: var(--font-mono);
    font-weight: 800;
    color: var(--accent);
    font-size: 1.05rem;
  }

  .rule-card p {
    font-size: 0.88rem;
    color: var(--muted);
    margin-block-start: 0.2rem;
  }

  /* Triage Layout */
  .triage-layout {
    display: grid;
    grid-template-columns: minmax(250px, 310px) 1fr;
    gap: 1.25rem;
    align-items: start;
  }

  @media (max-width: 820px) {
    .triage-layout {
      grid-template-columns: 1fr;
    }
  }

  .triage-sidebar {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1rem;
  }

  .triage-sidebar h2 {
    margin-block-end: 0.75rem;
    font-size: 1rem;
  }

  .symptom-list {
    display: grid;
    gap: 0.45rem;
  }

  .symptom-btn {
    inline-size: 100%;
    text-align: start;
    padding: 0.7rem 0.85rem;
    min-block-size: 44px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--surface-alt);
    cursor: pointer;
    display: grid;
    gap: 0.2rem;
  }

  .symptom-btn:hover {
    border-color: var(--accent);
  }

  .symptom-btn[aria-selected="true"] {
    background: var(--accent-subtle);
    border-color: var(--accent);
  }

  .symptom-btn strong {
    font-size: 0.94rem;
  }

  .symptom-btn span {
    font-size: 0.8rem;
    color: var(--muted);
  }

  .triage-detail {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: clamp(1rem, 2.5vw, 1.6rem);
    box-shadow: var(--shadow-sm);
  }

  .step-list {
    display: grid;
    gap: 1rem;
    margin-block: 1.15rem;
    padding: 0;
    list-style: none;
  }

  .step-card {
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1rem;
    background: var(--surface-alt);
  }

  .step-header {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
    margin-block-end: 0.45rem;
  }

  .step-title {
    font-weight: 700;
    font-size: 1rem;
  }

  .step-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-block-start: 0.65rem;
  }

  .suspect-links {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-block-start: 0.6rem;
  }

  /* Filter Chips */
  .filter-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-block-end: 1.25rem;
  }

  .chip, .chip-sm {
    min-block-size: 38px;
    padding: 0.35rem 0.85rem;
    border-radius: 999px;
    border: 1px solid var(--border);
    background: var(--surface);
    cursor: pointer;
    font-size: 0.86rem;
    font-weight: 600;
  }

  .chip-sm {
    min-block-size: 32px;
    padding: 0.2rem 0.65rem;
    font-size: 0.8rem;
    font-family: var(--font-mono);
  }

  .chip.active {
    background: var(--accent);
    color: var(--accent-contrast);
    border-color: var(--accent);
  }

  /* Components Workspace */
  .components-workspace {
    display: grid;
    grid-template-columns: minmax(260px, 340px) 1fr;
    gap: 1.25rem;
    align-items: start;
  }

  @media (max-width: 900px) {
    .components-workspace {
      grid-template-columns: 1fr;
    }
  }

  .component-selector-grid {
    display: grid;
    gap: 0.55rem;
  }

  .comp-nav-btn {
    inline-size: 100%;
    text-align: start;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.65rem 0.8rem;
    min-block-size: 54px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
    background: var(--surface);
    cursor: pointer;
  }

  .comp-nav-btn:hover {
    border-color: var(--accent);
  }

  .comp-nav-btn[aria-current="true"] {
    background: var(--accent-subtle);
    border-color: var(--accent);
  }

  .comp-symbol-mini {
    inline-size: 42px;
    block-size: 34px;
    flex-shrink: 0;
    color: var(--accent);
  }

  .comp-nav-text {
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
  }

  .comp-nav-text small {
    color: var(--muted);
    font-size: 0.78rem;
  }

  .component-detail-panel {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: clamp(1rem, 2.5vw, 1.65rem);
    box-shadow: var(--shadow-sm);
    container-type: inline-size;
  }

  .comp-hero {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding-block-end: 1rem;
    border-block-end: 1px solid var(--border);
    margin-block-end: 1.15rem;
  }

  .comp-hero-symbol {
    inline-size: 120px;
    block-size: 76px;
    padding: 0.5rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-alt);
    color: var(--accent);
  }

  .test-columns {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1rem;
    margin-block: 1rem;
  }

  .test-box {
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1rem;
    background: var(--surface-alt);
  }

  .test-box h3 {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
    margin-block-end: 0.6rem;
  }

  .test-box ol, .test-box ul {
    padding-inline-start: 1.2rem;
    display: grid;
    gap: 0.4rem;
    font-size: 0.93rem;
  }

  .callout {
    border-inline-start: 4px solid var(--accent);
    background: var(--accent-subtle);
    padding: 0.85rem 1rem;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    margin-block: 0.85rem;
  }

  .callout-warn {
    border-inline-start-color: var(--warn);
    background: var(--warn-bg);
  }

  .callout-advanced {
    border-inline-start-color: var(--ok);
    background: var(--ok-bg);
  }

  /* Multimeter interactive */
  .meter-interactive {
    display: grid;
    grid-template-columns: minmax(260px, 360px) 1fr;
    gap: 1.25rem;
    margin-block-end: 2rem;
  }

  @media (max-width: 820px) {
    .meter-interactive {
      grid-template-columns: 1fr;
    }
  }

  .meter-dial-panel,
  .meter-detail-card,
  .readings-cheat-sheet {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1.2rem;
  }

  .meter-mode-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.55rem;
    margin-block-start: 0.85rem;
  }

  .meter-mode-btn {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 0.15rem;
    padding: 0.7rem;
    min-block-size: 56px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--surface-alt);
    cursor: pointer;
    text-align: start;
  }

  .meter-mode-btn[aria-pressed="true"] {
    background: var(--accent-subtle);
    border-color: var(--accent);
  }

  .meter-symbol {
    font-family: var(--font-mono);
    font-weight: 800;
    font-size: 1.15rem;
    color: var(--accent);
  }

  .meter-specs {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
    gap: 0.75rem;
    margin-block: 1rem;
  }

  .spec-tile {
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 0.7rem;
  }

  .spec-tile small {
    display: block;
    color: var(--muted);
    font-size: 0.76rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
  }

  /* Tables */
  .table-scroll {
    overflow-x: auto;
    margin-block-start: 0.75rem;
  }

  table {
    inline-size: 100%;
    border-collapse: collapse;
    font-size: 0.92rem;
  }

  caption {
    text-align: start;
    font-weight: 600;
    color: var(--muted);
    margin-block-end: 0.5rem;
  }

  th, td {
    text-align: start;
    padding: 0.7rem 0.75rem;
    border-block-end: 1px solid var(--border);
    vertical-align: top;
  }

  th {
    background: var(--surface-alt);
    text-wrap: balance;
  }

  /* Calculators */
  .calc-grid,
  .safety-grid,
  .card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.15rem;
  }

  .calc-card,
  .info-card,
  .search-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 1.2rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
  }

  .calc-form label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    margin-block-end: 0.25rem;
  }

  .calc-form input,
  .calc-form select {
    inline-size: 100%;
    min-block-size: 40px;
    padding: 0.4rem 0.65rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-alt);
    font-family: var(--font-mono);
    color: var(--text);
  }

  .input-row {
    display: flex;
    gap: 0.5rem;
  }

  .form-grid-2 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.6rem;
  }

  .form-grid-3 {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.6rem;
  }

  .band-select-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
    gap: 0.55rem;
  }

  .band-mode-row {
    display: flex;
    gap: 0.4rem;
  }

  .chip-sm.active {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
  }

  .resistor-preview {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 0;
  }

  .resistor-lead {
    height: 4px;
    width: 28px;
    background: #9ca3af;
    border-radius: 2px;
  }

  .resistor-body {
    display: flex;
    align-items: stretch;
    justify-content: space-evenly;
    min-width: 170px;
    height: 34px;
    padding: 0 14px;
    border-radius: 10px;
    border: 1px solid rgba(0, 0, 0, 0.2);
    box-shadow: inset 0 -3px 6px rgba(0, 0, 0, 0.14);
  }

  .resistor-body.carbon {
    background: #d9b88c;
  }

  .resistor-body.metal {
    background: #5b9bd5;
  }

  .resistor-band {
    width: 11px;
    height: 100%;
    border-inline: 1px solid rgba(0, 0, 0, 0.15);
  }

  .resistor-band.tol-band {
    margin-inline-start: 10px;
  }

  @media (max-width: 520px) {
    .form-grid-2,
    .form-grid-3 {
      grid-template-columns: 1fr;
    }
  }

  .calc-result {
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 0.85rem;
    font-family: var(--font-mono);
    font-size: 0.95rem;
  }

  .preset-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
  }

  .danger-card {
    border-color: var(--danger);
  }

  details {
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-alt);
  }

  summary {
    padding: 0.75rem 0.9rem;
    font-weight: 700;
    cursor: pointer;
    min-block-size: 44px;
    display: flex;
    align-items: center;
  }

  .details-body {
    padding: 0 0.9rem 0.9rem;
    font-size: 0.92rem;
  }

  .details-body ul {
    padding-inline-start: 1.2rem;
    display: grid;
    gap: 0.4rem;
  }

  /* Experience-level visibility */
  :root[data-skill="novice"] .only-advanced {
    display: none;
  }

  :root[data-skill="advanced"] .only-novice {
    display: none;
  }

  @media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
      transition-duration: 0.01ms !important;
      scroll-behavior: auto !important;
    }
  }
}

@layer utilities {
  .visually-hidden:where(:not(:focus-within, :active)) {
    position: absolute !important;
    clip-path: inset(50%) !important;
    overflow: hidden !important;
    width: 1px !important;
    height: 1px !important;
    margin: -1px !important;
    padding: 0 !important;
    border: 0 !important;
    white-space: nowrap !important;
  }
}