/* ============================================================================
   Electronics Fundamentals Reference — scoped styles
   Uses site-wide CSS variables (--c-bg, --c-surface, --c-text, --c-accent…)
   defined in assets/css/style.css, so dark/light theme switching is automatic.

   Mirrors the structural patterns of assets/css/spectrum.css so the page
   reads as a sibling reference. BEM with the "electronics-" prefix.
   ========================================================================== */

.electronics-page {
  padding: var(--space-2xl) 0 var(--space-3xl);
}

.electronics-container {
  max-width: 80rem;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* ---- Hero ---- */
.electronics-hero { margin-bottom: var(--space-xl); }
.electronics-eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.75rem;
  color: var(--c-accent);
  margin: 0 0 var(--space-sm);
  font-weight: 600;
}
.electronics-title {
  font-size: clamp(1.75rem, 1.4rem + 1.5vw, 2.75rem);
  margin: 0 0 var(--space-md);
  line-height: 1.15;
  color: var(--c-text);
}
.electronics-lede {
  font-size: 1.05rem;
  line-height: 1.65;
  color: var(--c-text);
  margin: 0 0 var(--space-md);
  max-width: 60rem;
}
.electronics-howto {
  font-size: 0.95rem;
  color: var(--c-text-muted);
  margin: 0 0 var(--space-lg);
  max-width: 60rem;
}
.electronics-howto strong { color: var(--c-text); }
.electronics-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  font-size: 0.85rem;
  color: var(--c-text-muted);
}
.electronics-meta__item strong {
  color: var(--c-accent);
  font-variant-numeric: tabular-nums;
}

/* ---- Safety disclaimer ---- */
.electronics-disclaimer {
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.35);
  border-left: 4px solid #f59e0b;
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  margin: var(--space-lg) 0;
  color: var(--c-text);
}
[data-theme="light"] .electronics-disclaimer {
  background: #fff8e1;
  border-color: rgba(180, 83, 9, 0.35);
  border-left-color: #d97706;
  color: #5c4500;
}
.electronics-disclaimer h3 {
  margin: 0 0 0.5rem;
  font-size: 1rem;
  font-weight: 600;
  color: #fbbf24;
}
[data-theme="light"] .electronics-disclaimer h3 {
  color: #b45309;
}
.electronics-disclaimer p {
  margin: 0;
  line-height: 1.6;
  font-size: 0.95rem;
  color: inherit;
}

/* ============================================================================
   Generic section scaffold — every locked section uses .electronics-section
   so headings, intros, and bottom margins stay consistent without per-section
   tweaks.
   ========================================================================== */
.electronics-section {
  margin-top: var(--space-2xl);
  scroll-margin-top: calc(var(--header-height, 3.75rem) + var(--space-md));
}
.electronics-section + .electronics-section {
  border-top: 1px solid var(--c-border-light);
  padding-top: var(--space-2xl);
}
.electronics-section__title {
  font-size: clamp(1.25rem, 1.05rem + 0.8vw, 1.65rem);
  margin: 0 0 var(--space-sm);
  color: var(--c-text);
  letter-spacing: -0.005em;
}
.electronics-section__intro {
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--c-text-muted);
  margin: 0 0 var(--space-lg);
  max-width: 56rem;
}

/* ============================================================================
   Reusable card primitive — formula cards, calculator cards, component cards,
   and design-guide cards all share .electronics-card so future content batches
   only need to fill markup.
   ========================================================================== */
.electronics-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  box-shadow: 0 4px 16px var(--c-card-shadow);
  transition: border-color var(--transition-fast),
              transform var(--transition-fast),
              box-shadow var(--transition-fast);
}
.electronics-card:hover {
  border-color: var(--c-accent-border);
}
.electronics-card__title {
  margin: 0 0 var(--space-sm);
  font-size: 1rem;
  font-weight: 600;
  color: var(--c-text);
}
.electronics-card__subtitle {
  margin: -0.25rem 0 var(--space-sm);
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--c-accent);
}
.electronics-card__body {
  font-size: 0.92rem;
  line-height: 1.6;
  color: var(--c-text);
}
.electronics-card__footer {
  margin-top: var(--space-md);
  padding-top: var(--space-sm);
  border-top: 1px solid var(--c-border-light);
  font-size: 0.82rem;
  color: var(--c-text-muted);
}

/* ============================================================================
   Section 1 — Quick Reference Wheel
   Square-aspect container that holds the interactive radial nav. Sized
   responsively so the inscribed wheel always has equal room top/bottom.
   ========================================================================== */
.electronics-wheel {
  position: relative;
  width: 100%;
  max-width: 36rem;
  margin: 0 auto;
  aspect-ratio: 1 / 1;
  border-radius: 50%;
  background:
    radial-gradient(circle at center,
      var(--c-surface) 0%,
      var(--c-surface) 55%,
      var(--c-surface-alt) 100%);
  border: 1px solid var(--c-border);
  box-shadow: 0 8px 28px var(--c-card-shadow);
}
.electronics-wheel__hub {
  position: absolute;
  inset: 50% auto auto 50%;
  transform: translate(-50%, -50%);
  width: 38%;
  height: 38%;
  border-radius: 50%;
  background: var(--c-surface-alt);
  border: 1px solid var(--c-border);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-weight: 600;
  color: var(--c-text-muted);
  font-size: 0.9rem;
}
.electronics-wheel__spoke {
  position: absolute;
  width: 28%;
  text-align: center;
  font-size: 0.85rem;
  color: var(--c-text);
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: 0.5rem 0.75rem;
  transition: border-color var(--transition-fast),
              transform var(--transition-fast);
}
.electronics-wheel__spoke:hover {
  border-color: var(--c-accent-border);
  color: var(--c-accent);
}

/* ============================================================================
   Section 2 — Core Formulas & Laws
   A simple responsive grid of formula cards. Each card centers its formula
   and uses a monospace font for the equation itself.
   ========================================================================== */
.electronics-formulas {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-md);
}
.electronics-formula-card {
  /* Inherits from .electronics-card; this class adds formula-specific layout. */
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  box-shadow: 0 4px 16px var(--c-card-shadow);
  transition: border-color var(--transition-fast),
              transform var(--transition-fast);
}
.electronics-formula-card:hover {
  border-color: var(--c-accent-border);
}
.electronics-formula-card__name {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--c-text);
}
.electronics-formula-card__equation {
  font-family: var(--f-mono);
  font-size: 1.1rem;
  text-align: center;
  padding: var(--space-sm) var(--space-md);
  background: var(--c-code-bg);
  border: 1px solid var(--c-border-light);
  border-radius: var(--border-radius-sm);
  color: var(--c-accent);
  font-variant-numeric: tabular-nums;
  overflow-x: auto;
}
.electronics-formula-card__legend {
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 0.82rem;
  color: var(--c-text-muted);
  display: grid;
  gap: 0.2rem;
}
.electronics-formula-card__legend li {
  display: flex;
  gap: 0.4rem;
}
.electronics-formula-card__legend strong {
  color: var(--c-text);
  font-family: var(--f-mono);
  min-width: 1.5rem;
}

/* ============================================================================
   Section 3 — Interactive Calculators
   Card grid where each card holds inputs, a result line, and a tiny "reset"
   affordance. Dark-only by default, light-theme overrides via [data-theme].
   ========================================================================== */
.electronics-calculators {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
}
.electronics-calculator {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  box-shadow: 0 4px 16px var(--c-card-shadow);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}
.electronics-calculator__title {
  margin: 0;
  font-size: 1rem;
  font-weight: 600;
  color: var(--c-text);
}
.electronics-calculator__hint {
  margin: 0;
  font-size: 0.82rem;
  color: var(--c-text-muted);
  line-height: 1.5;
}
.electronics-calculator__field {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  font-size: 0.85rem;
  color: var(--c-text-muted);
}
.electronics-calculator__field label {
  font-weight: 500;
}
.electronics-calculator__input {
  appearance: none;
  background: var(--c-bg-alt);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius-sm);
  color: var(--c-text);
  font: inherit;
  font-family: var(--f-mono);
  font-size: 0.92rem;
  padding: 0.45rem 0.65rem;
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast);
}
.electronics-calculator__input:focus {
  outline: none;
  border-color: var(--c-accent-border);
  box-shadow: 0 0 0 3px var(--c-accent-bg);
}
.electronics-calculator__select {
  appearance: none;
  background: var(--c-bg-alt);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius-sm);
  color: var(--c-text);
  font: inherit;
  font-size: 0.88rem;
  padding: 0.4rem 0.6rem;
  cursor: pointer;
}
.electronics-calculator__result {
  margin-top: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--c-accent-bg);
  border: 1px solid var(--c-accent-border);
  border-radius: var(--border-radius-sm);
  color: var(--c-accent);
  font-family: var(--f-mono);
  font-size: 1rem;
  font-variant-numeric: tabular-nums;
  text-align: center;
}
.electronics-calculator__reset {
  align-self: flex-start;
  appearance: none;
  background: transparent;
  border: 1px solid var(--c-border);
  border-radius: 999px;
  color: var(--c-text-muted);
  padding: 0.25rem 0.7rem;
  font: inherit;
  font-size: 0.78rem;
  cursor: pointer;
  transition: border-color var(--transition-fast),
              color var(--transition-fast);
}
.electronics-calculator__reset:hover {
  color: var(--c-text);
  border-color: var(--c-accent-border);
}

/* ============================================================================
   Section 4 — Component References & Charts
   Resistor color codes, capacitor markings, etc. Two-column grid on desktop;
   a generic chart container holds anything that needs an aspect-locked area.
   ========================================================================== */
.electronics-components {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-lg);
}
.electronics-component-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  box-shadow: 0 4px 16px var(--c-card-shadow);
}
.electronics-component-card__title {
  margin: 0 0 var(--space-sm);
  font-size: 1rem;
  font-weight: 600;
  color: var(--c-text);
}
.electronics-component-card__caption {
  margin: var(--space-sm) 0 0;
  font-size: 0.82rem;
  color: var(--c-text-muted);
  line-height: 1.5;
}

.electronics-chart-container {
  position: relative;
  width: 100%;
  background: var(--c-bg-alt);
  border: 1px solid var(--c-border-light);
  border-radius: var(--border-radius-sm);
  padding: var(--space-md);
  overflow: auto;
}
.electronics-chart-container--square { aspect-ratio: 1 / 1; }
.electronics-chart-container--wide   { aspect-ratio: 16 / 9; }

/* Resistor color-band swatches, used by the resistor color-code chart. */
.electronics-color-band {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.5rem;
  height: 1.5rem;
  border-radius: var(--border-radius-sm);
  border: 1px solid rgba(0, 0, 0, 0.25);
  font-size: 0.75rem;
  font-weight: 600;
  color: #ffffff;
  text-shadow: 0 1px 1px rgba(0, 0, 0, 0.45);
}
.electronics-color-band--black  { background: #111111; }
.electronics-color-band--brown  { background: #8b4513; }
.electronics-color-band--red    { background: #d42d2d; }
.electronics-color-band--orange { background: #ff8c00; color: #111111; text-shadow: none; }
.electronics-color-band--yellow { background: #ffd400; color: #111111; text-shadow: none; }
.electronics-color-band--green  { background: #3aa14b; }
.electronics-color-band--blue   { background: #2563eb; }
.electronics-color-band--violet { background: #8b5cf6; }
.electronics-color-band--gray   { background: #6b7280; }
.electronics-color-band--white  { background: #f9fafb; color: #111111; text-shadow: none; }
.electronics-color-band--gold   { background: linear-gradient(135deg, #d4a017, #f0c957); color: #3a2a00; text-shadow: none; }
.electronics-color-band--silver { background: linear-gradient(135deg, #9aa0a6, #d0d4d8); color: #1a1a1a; text-shadow: none; }

/* ============================================================================
   Section 5 — Circuit Design Guides & Practical Tips
   Tip cards stacked in a single column on mobile, two columns on wider
   screens. Each tip carries an optional "callout" tag for severity/category.
   ========================================================================== */
.electronics-guides {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-lg);
}
.electronics-guide {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-left: 3px solid var(--c-accent);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  box-shadow: 0 4px 16px var(--c-card-shadow);
}
.electronics-guide__tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.15rem 0.55rem;
  border-radius: 999px;
  background: var(--c-accent-bg);
  color: var(--c-accent);
  border: 1px solid var(--c-accent-border);
  margin-bottom: var(--space-sm);
}
.electronics-guide__tag--warning {
  background: rgba(245, 158, 11, 0.12);
  color: #fbbf24;
  border-color: rgba(245, 158, 11, 0.35);
}
[data-theme="light"] .electronics-guide__tag--warning {
  color: #b45309;
}
.electronics-guide__tag--danger {
  background: rgba(239, 68, 68, 0.12);
  color: #f87171;
  border-color: rgba(239, 68, 68, 0.35);
}
.electronics-guide__title {
  margin: 0 0 var(--space-sm);
  font-size: 1rem;
  font-weight: 600;
  color: var(--c-text);
}
.electronics-guide__body {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.6;
  color: var(--c-text);
}
.electronics-guide__body p { margin: 0 0 var(--space-sm); }
.electronics-guide__body p:last-child { margin-bottom: 0; }

/* ============================================================================
   Section 6 — Reference Tables
   SI prefixes, conversions, schematic symbols. Wrapper provides horizontal
   scroll on small viewports while keeping desktop tables flush.
   ========================================================================== */
.electronics-tables {
  display: grid;
  gap: var(--space-lg);
}
.electronics-table-wrapper {
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  background: var(--c-surface);
  box-shadow: 0 4px 16px var(--c-card-shadow);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.electronics-table-wrapper:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}
.electronics-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  font-size: 0.9rem;
  color: var(--c-text);
}
.electronics-table thead th {
  position: sticky;
  top: 0;
  z-index: 1;
  background: var(--c-surface-alt);
  color: var(--c-text);
  text-align: left;
  font-weight: 600;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 0.85rem 1rem 0.7rem;
  border-bottom: 2px solid var(--c-border);
}
.electronics-table tbody td {
  padding: 0.7rem 1rem;
  vertical-align: top;
  border-bottom: 1px solid var(--c-border-light);
  line-height: 1.5;
}
.electronics-table tbody tr:hover td { background: var(--c-surface-alt); }
.electronics-table tbody tr:last-child td { border-bottom: 0; }
.electronics-table .mono,
.electronics-table .col-mono {
  font-family: var(--f-mono);
  font-size: 0.84rem;
  font-variant-numeric: tabular-nums;
  color: var(--c-text);
}

/* Caption / heading row used inside reference-table containers. */
.electronics-table-caption {
  caption-side: top;
  text-align: left;
  padding: 0.85rem 1rem;
  color: var(--c-text-muted);
  font-size: 0.82rem;
  border-bottom: 1px solid var(--c-border-light);
  background: var(--c-surface-alt);
}

/* ============================================================================
   Collapsibles (used by formula derivations, calculator hints, etc.)
   Mirrors the .cell-collapse pattern from spectrum.css.
   ========================================================================== */
.electronics-collapse { font-size: inherit; }
.electronics-collapse > summary {
  list-style: none;
  cursor: pointer;
  display: inline-flex;
  align-items: baseline;
  gap: 0.5rem;
  flex-wrap: wrap;
  color: var(--c-text);
  user-select: none;
}
.electronics-collapse > summary::-webkit-details-marker { display: none; }
.electronics-collapse > summary::marker { display: none; content: ""; }
.electronics-collapse__label { color: var(--c-text-muted); }
.electronics-collapse__more {
  font-size: 0.75rem;
  color: var(--c-accent);
  text-decoration: underline;
  text-underline-offset: 2px;
  text-decoration-thickness: 1px;
}
.electronics-collapse[open] > summary .electronics-collapse__more::after { content: " (collapse)"; }

/* ============================================================================
   Utilities
   ========================================================================== */
.electronics-mono {
  font-family: var(--f-mono);
  font-size: 0.84rem;
  color: var(--c-text);
  font-variant-numeric: tabular-nums;
}
.electronics-pill {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.15rem 0.55rem;
  border-radius: 999px;
  background: var(--c-surface-alt);
  border: 1px solid var(--c-border);
  color: var(--c-text-muted);
}
.electronics-pill--accent {
  background: var(--c-accent-bg);
  border-color: var(--c-accent-border);
  color: var(--c-accent);
}

/* ============================================================================
   Responsive — small screens
   ========================================================================== */
@media (max-width: 640px) {
  .electronics-container { padding: 0 var(--space-md); }
  .electronics-section { margin-top: var(--space-xl); }
  .electronics-section + .electronics-section { padding-top: var(--space-xl); }
  .electronics-formulas,
  .electronics-calculators,
  .electronics-components,
  .electronics-guides {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }
  .electronics-card,
  .electronics-formula-card,
  .electronics-calculator,
  .electronics-component-card,
  .electronics-guide {
    padding: var(--space-md);
  }
  .electronics-wheel { max-width: 100%; }
}

/* ============================================================================
   Reduced motion
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  .electronics-card,
  .electronics-formula-card,
  .electronics-calculator__input,
  .electronics-calculator__reset,
  .electronics-wheel__spoke {
    transition: none;
  }
}

/* ============================================================================
   Print
   Strip backgrounds, drop shadows, and force single-column layout so the
   reference reads as a clean cheat sheet on paper.
   ========================================================================== */
@media print {
  .electronics-page { padding: 0; }
  .electronics-container { max-width: none; padding: 0; }
  /* Keep cards intact across page breaks. The legacy `page-break-inside`
     alias is paired with the modern `break-inside` so older WebKit /
     Blink renderers (Chromium pre-83, Safari pre-15) honour the rule
     when they're driving a print job. */
  .electronics-hero,
  .electronics-section,
  .electronics-card,
  .electronics-formula-card,
  .electronics-component-card,
  .electronics-guide,
  .electronics-calculator,
  .electronics-table-wrapper {
    break-inside: avoid;
    page-break-inside: avoid;
  }
  .electronics-card,
  .electronics-formula-card,
  .electronics-calculator,
  .electronics-component-card,
  .electronics-guide,
  .electronics-table-wrapper,
  .electronics-wheel {
    box-shadow: none;
    border-color: #999;
    background: #ffffff;
    color: #111111;
  }
  .electronics-formulas,
  .electronics-calculators,
  .electronics-components,
  .electronics-guides {
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
  }
  .electronics-disclaimer {
    background: #fff8e1;
    color: #5c4500;
    border-color: #d97706;
  }
  .electronics-formula-card__equation {
    background: #f4f4f4;
    color: #111111;
    border-color: #ccc;
  }
}

/* ============================================================================
   SECTION 7 — Page-level chrome (Batch 3 extraction)
   Originally inline <style> blocks in the HTML, moved here per audit
   recommendation #1. Order preserved exactly so cascade behavior matches.
   ============================================================================ */

/* ---- 7.1 — Top-of-page chrome (TOC / floating reset / footer / Section-4 chrome) ---- */
      /* z-index ladder for top-of-page chrome:
         site header (global)        — topmost
         TOC right-rail              — 11
         help `?` / mobile `≡`       — 10
         abbreviations sticky summary — 9 (in abbreviations.css)
         Keep TOC > summary so the rail is never obscured. */
      .electronics-toc {
        position: fixed;
        top: calc(var(--header-height, 3.75rem) + 0.5rem);
        right: var(--space-md);
        width: 12rem;
        max-height: calc(100vh - var(--header-height, 3.75rem) - 2 * var(--space-md));
        overflow-y: auto;
        padding: var(--space-sm) var(--space-md);
        background: var(--c-surface);
        border: 1px solid var(--c-border);
        border-radius: var(--border-radius);
        box-shadow: 0 4px 16px var(--c-card-shadow);
        font-size: 0.85rem;
        z-index: 11;
        display: none;
      }
      @media (min-width: 1280px) {
        .electronics-toc { display: block; }
      }
      .electronics-toc__title {
        margin: 0 0 0.4rem;
        font-size: 0.7rem;
        letter-spacing: 0.08em;
        text-transform: uppercase;
        color: var(--c-text-muted);
        font-weight: 600;
      }
      .electronics-toc ol {
        list-style: none;
        margin: 0;
        padding: 0;
        display: flex;
        flex-direction: column;
        gap: 0.15rem;
      }
      .electronics-toc a {
        display: block;
        padding: 0.35rem 0.5rem;
        border-left: 2px solid transparent;
        border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
        color: var(--c-text-muted);
        text-decoration: none;
        transition: background var(--transition-fast),
                    border-color var(--transition-fast),
                    color var(--transition-fast);
      }
      .electronics-toc a:hover {
        color: var(--c-text);
        background: var(--c-surface-alt);
      }
      .electronics-toc a.is-active {
        color: var(--c-accent);
        border-left-color: var(--c-accent);
        background: var(--c-accent-bg);
        font-weight: 600;
      }

      .electronics-floating-reset {
        position: fixed;
        /* Lift above the page footer so they don't overlap on short
           pages where both compete for the bottom-right corner. The
           env(safe-area-inset-bottom) addition keeps clearance under
           iOS Safari's home-bar overlay. JS additionally adds the
           .is-stowed modifier when the footer is on-screen. */
        bottom: calc(1.5rem + env(safe-area-inset-bottom, 0px));
        right: var(--space-md);
        z-index: 60;
        appearance: none;
        background: var(--c-surface);
        color: var(--c-text);
        border: 1px solid var(--c-border);
        border-radius: 999px;
        padding: 0.55rem 1.1rem;
        font: inherit;
        font-size: 0.85rem;
        font-weight: 600;
        cursor: pointer;
        box-shadow: 0 6px 24px var(--c-card-shadow);
        transition: background var(--transition-fast),
                    color var(--transition-fast),
                    border-color var(--transition-fast),
                    transform var(--transition-fast),
                    opacity var(--transition-fast);
      }
      .electronics-floating-reset.is-stowed {
        opacity: 0;
        pointer-events: none;
        transform: translateY(0.5rem);
      }
      .electronics-floating-reset:hover {
        color: var(--c-accent);
        border-color: var(--c-accent-border);
        transform: translateY(-1px);
      }
      .electronics-floating-reset:focus-visible {
        outline: 2px solid var(--c-accent);
        outline-offset: 3px;
      }
      .electronics-floating-reset[hidden] { display: none; }

      .electronics-bookmark-btn::before { content: ""; }
      /* Lightweight emphasis so the bookmark button reads as a "save" action
         even when it sits next to Clear / Copy / Open-in-Wheel siblings.
         font-family: prepend the platform colour-emoji fonts so the
         🔖 and 🔗 glyphs render in colour on Windows (which otherwise
         falls back to monochrome) while still letting the Latin label
         pick up the body face from the font stack. */
      .electronics-bookmark-btn,
      .electronics-share-btn {
        font-weight: 600;
        font-family: "Apple Color Emoji", "Segoe UI Emoji",
                     "Segoe UI Symbol", "Noto Color Emoji",
                     system-ui, var(--f-body, sans-serif);
      }
      .electronics-share-btn:hover,
      .electronics-bookmark-btn:hover {
        color: var(--c-accent);
        border-color: var(--c-accent-border);
      }

      /* Value-cloud chips are real <button> elements (Batch 9.9). Strip the
         browser default chrome so the existing .electronics-eseries-value
         visuals stay intact, plus a focus ring for keyboard users. */
      button.electronics-eseries-value {
        appearance: none;
        -webkit-appearance: none;
        font: inherit;
        cursor: pointer;
        line-height: 1;
        transition: transform var(--transition-fast),
                    color var(--transition-fast),
                    border-color var(--transition-fast),
                    background var(--transition-fast);
      }
      button.electronics-eseries-value:hover {
        color: var(--c-accent);
        border-color: var(--c-accent-border);
        transform: translateY(-1px);
      }
      button.electronics-eseries-value:focus-visible {
        outline: 2px solid var(--c-accent);
        outline-offset: 2px;
      }

      .electronics-footer {
        margin-top: var(--space-2xl);
        padding: var(--space-lg) 0 var(--space-2xl);
        border-top: 1px solid var(--c-border-light);
        display: flex;
        flex-wrap: wrap;
        gap: var(--space-md);
        align-items: baseline;
        font-size: 0.82rem;
        color: var(--c-text-muted);
      }
      .electronics-footer__version {
        font-family: var(--f-mono);
        font-variant-numeric: tabular-nums;
        background: var(--c-surface-alt);
        border: 1px solid var(--c-border);
        border-radius: var(--border-radius-sm);
        padding: 0.15rem 0.55rem;
      }

      /* Live resistor preview SVG (Section 4). The container locks a
         5:1 aspect ratio so the body never collapses into an
         illegibly thin sliver on narrow screens; the SVG inside
         fills the box without distortion via preserveAspectRatio. */
      .electronics-rcd-resistor-preview {
        margin: var(--space-md) auto;
        max-width: 22rem;
        color: var(--c-text-muted);
        aspect-ratio: 5 / 1;
        width: 100%;
      }
      .electronics-rcd-resistor-preview svg {
        width: 100%;
        height: 100%;
        display: block;
      }

      /* Pseudo-3D tilt on swatches — pure CSS. Hover fires on pointer
         devices; :active + :focus-visible give tap / keyboard users
         the same affordance on mobile and via assistive tech. */
      .electronics-rcd-swatch {
        perspective: 600px;
        transform-style: preserve-3d;
      }
      .electronics-rcd-swatch:hover,
      .electronics-rcd-swatch:active,
      .electronics-rcd-swatch:focus-visible {
        transform: scale(1.06) rotateX(8deg) rotateY(-6deg);
      }
      .electronics-rcd-swatch.is-active:hover,
      .electronics-rcd-swatch.is-active:active,
      .electronics-rcd-swatch.is-active:focus-visible {
        transform: scale(1.10) rotateX(8deg) rotateY(-6deg);
      }
      /* Light-theme contrast fix for white / yellow / silver chips —
         their backgrounds are too pale to read against the light
         page, so use a darker, thicker themed border + a faint inset
         shadow to reach AA contrast against the surrounding card. */
      [data-theme="light"] .electronics-rcd-swatch[data-color="white"],
      [data-theme="light"] .electronics-rcd-swatch[data-color="yellow"],
      [data-theme="light"] .electronics-rcd-swatch[data-color="silver"] {
        border: 1.5px solid var(--c-text);
        box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.10);
      }

      /* E-series "value cloud" — popularity-derived font sizes. JS adds
         the .electronics-eseries-value--tN modifier (1..4). */
      .electronics-eseries-value--t1 { font-size: 0.7rem;  opacity: 0.65; }
      .electronics-eseries-value--t2 { font-size: 0.82rem; opacity: 0.85; }
      .electronics-eseries-value--t3 { font-size: 0.95rem; }
      .electronics-eseries-value--t4 {
        font-size: 1.1rem;
        font-weight: 700;
        background: var(--c-accent-bg);
        border-color: var(--c-accent-border);
        color: var(--c-accent);
      }

      /* Tolerance-chart toggle (Section 4). Default = chart hidden, CSS
         fallback visible. The fallback shows nested rectangles whose width
         matches each tolerance class's spread relative to ±20%. */
      .electronics-rcd-chart-wrapper {
        display: none;
      }
      .electronics-rcd-chart-wrapper.is-shown {
        display: block;
      }
      .electronics-rcd-chart-fallback {
        position: relative;
        height: 200px;
        margin: 0 0 var(--space-md);
        padding: var(--space-sm) var(--space-md);
        background: var(--c-bg-alt);
        border: 1px solid var(--c-border-light);
        border-radius: var(--border-radius-sm);
        display: flex;
        flex-direction: column;
        justify-content: space-around;
      }
      .electronics-rcd-chart-fallback.is-hidden { display: none; }
      .electronics-rcd-chart-fallback__row {
        display: grid;
        grid-template-columns: 4rem minmax(0, 1fr);
        gap: 0.5rem;
        align-items: center;
        font-size: 0.78rem;
        font-family: var(--f-mono);
        font-variant-numeric: tabular-nums;
      }
      .electronics-rcd-chart-fallback__label {
        color: var(--c-text-muted);
        text-align: right;
      }
      .electronics-rcd-chart-fallback__bar {
        position: relative;
        height: 1.2rem;
        background: var(--c-border);
        border-radius: 4px;
      }
      .electronics-rcd-chart-fallback__fill {
        position: absolute;
        top: 0;
        height: 100%;
        background: var(--fallback-color, var(--c-accent));
        border-radius: 4px;
        opacity: 0.85;
      }
      .electronics-rcd-chart-toggle {
        /* Made more prominent (Batch 4): bigger pill, accent border by
           default, hover lift, and a small chart-icon glyph — so the
           "you can also see this as a chart" affordance stops getting
           lost between the tolerance bar and the Reset / Copy /
           Open-in-Quick-Wheel actions row. */
        appearance: none;
        display: inline-flex;
        align-items: center;
        gap: 0.4rem;
        background: var(--c-surface);
        border: 1.5px solid var(--c-accent-border);
        color: var(--c-accent);
        border-radius: 999px;
        padding: 0.5rem 1.05rem;
        font: inherit;
        font-size: 0.88rem;
        font-weight: 600;
        cursor: pointer;
        margin-bottom: var(--space-md);
        box-shadow: 0 2px 8px var(--c-card-shadow);
        transition: background var(--transition-fast),
                    color var(--transition-fast),
                    border-color var(--transition-fast),
                    transform var(--transition-fast),
                    box-shadow var(--transition-fast);
      }
      .electronics-rcd-chart-toggle:hover {
        background: var(--c-accent-bg);
        color: var(--c-accent);
        border-color: var(--c-accent);
        transform: translateY(-1px);
        box-shadow: 0 4px 14px var(--c-card-shadow);
      }
      .electronics-rcd-chart-toggle:focus-visible {
        outline: 2px solid var(--c-accent);
        outline-offset: 2px;
      }
      .electronics-rcd-chart-toggle[aria-pressed="true"] {
        background: var(--c-accent-bg);
        color: var(--c-accent);
        border-color: var(--c-accent);
      }

      @media print {
        /* Hide interactive chrome that doesn't print well. The mobile TOC
           trigger + drawer, the share button, and the help-trigger join
           the existing toc / floating-reset / chart-toggle / bookmark
           hides so the paper copy is read-only content. */
        .electronics-toc,
        .electronics-toc-trigger,
        .electronics-toc-drawer,
        .electronics-floating-reset,
        .electronics-rcd-chart-toggle,
        .electronics-bookmark-btn,
        .electronics-share-btn,
        .electronics-help-trigger,
        .electronics-modal-backdrop,
        canvas.electronics-rcd-resistor-preview,
        .electronics-rcd-chart-wrapper canvas,
        .electronics-ohms-chart-wrapper canvas,
        .electronics-led-chart-wrapper canvas,
        .electronics-divider-chart-wrapper canvas,
        .electronics-rc-chart-wrapper canvas,
        .electronics-wheel-chart-wrapper canvas,
        .electronics-sp-chart-wrapper canvas {
          display: none !important;
        }
        /* Force the CSS fallback bar visible on print so a paper copy still
           communicates tolerance ranges. */
        .electronics-rcd-chart-fallback.is-hidden { display: flex !important; }
        /* Enlarge formula equations for paper readability. */
        .electronics-formula-card__equation {
          font-size: 1.3rem !important;
          line-height: 1.5;
        }
        /* Resistor preview prints in colour. */
        .electronics-rcd-resistor-preview svg {
          color: #111 !important;
        }
      }

/* ---- 7.2 — Section 1: Quick Reference Wheel ---- */
        .electronics-wheel-layout {
          display: grid;
          grid-template-columns: repeat(auto-fit, minmax(20rem, 1fr));
          gap: var(--space-xl);
          align-items: center;
        }
        .electronics-wheel-svg { width: 100%; height: 100%; display: block; }
        .electronics-wheel__quadrant { cursor: pointer; transition: opacity var(--transition-fast); }
        .electronics-wheel__quadrant:hover { opacity: 0.9; }
        .electronics-wheel__quadrant:focus { outline: none; }
        .electronics-wheel__quadrant-bg {
          fill: transparent;
          stroke: transparent;
          stroke-width: 2;
          transition: fill var(--transition-fast), stroke var(--transition-fast);
        }
        .electronics-wheel__quadrant:hover .electronics-wheel__quadrant-bg,
        .electronics-wheel__quadrant.is-focused .electronics-wheel__quadrant-bg {
          fill: var(--c-accent-bg);
        }
        .electronics-wheel__quadrant:focus-visible .electronics-wheel__quadrant-bg {
          stroke: var(--c-accent);
          fill: var(--c-accent-bg);
        }
        .electronics-wheel__symbol {
          font-size: 2.4rem;
          font-weight: 700;
          fill: var(--c-text);
          transition: fill var(--transition-fast);
        }
        .electronics-wheel__quadrant.is-focused .electronics-wheel__symbol { fill: var(--c-accent); }
        .electronics-wheel__formula {
          font-size: 0.78rem;
          font-family: var(--f-mono);
          fill: var(--c-text-muted);
        }
        .electronics-wheel__divider { stroke: var(--c-border); stroke-width: 1; opacity: 0.6; }

        /* Brief accent-coloured flash to signal a quadrant whose value
           was just driven by setExternalValues (e.g. "Open in Quick
           Wheel" from a formula card). The keyframe animates the
           quadrant background from a soft accent fill back to
           transparent so the wheel returns to its neutral resting
           state without a hard pop. */
        .electronics-wheel__quadrant.is-flash .electronics-wheel__quadrant-bg {
          animation: electronics-wheel-flash 700ms ease-out;
        }
        @keyframes electronics-wheel-flash {
          0%   { fill: var(--c-accent-bg); stroke: var(--c-accent); }
          60%  { fill: var(--c-accent-bg); stroke: var(--c-accent); }
          100% { fill: transparent;        stroke: transparent;     }
        }
        @media (prefers-reduced-motion: reduce) {
          .electronics-wheel__quadrant.is-flash .electronics-wheel__quadrant-bg {
            animation-duration: 1ms;
          }
        }

        .electronics-wheel-fields {
          display: grid;
          grid-template-columns: repeat(2, minmax(0, 1fr));
          gap: var(--space-sm);
        }
        .electronics-wheel-field--computed input {
          color: var(--c-accent);
          font-weight: 600;
        }
        .electronics-wheel-field--computed label::after {
          content: " · solved";
          font-size: 0.7rem;
          color: var(--c-accent);
          letter-spacing: 0.04em;
          text-transform: uppercase;
          margin-left: 0.25rem;
        }

        .electronics-wheel-status {
          font-size: 0.85rem;
          padding: var(--space-sm) var(--space-md);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius-sm);
          background: var(--c-surface-alt);
          color: var(--c-text-muted);
          line-height: 1.5;
          font-variant-numeric: tabular-nums;
        }
        .electronics-wheel-status--ok { color: var(--c-text); border-color: var(--c-accent-border); }
        .electronics-wheel-status--warn {
          background: rgba(245, 158, 11, 0.12);
          border-color: rgba(245, 158, 11, 0.35);
          color: #fbbf24;
        }
        [data-theme="light"] .electronics-wheel-status--warn { color: #b45309; }

        .electronics-wheel-chart-wrapper {
          position: relative;
          height: 220px;
          background: var(--c-bg-alt);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          padding: var(--space-sm);
        }
        .electronics-wheel-chart-label {
          margin: 0;
          text-align: center;
          font-size: 0.75rem;
          color: var(--c-text-muted);
          letter-spacing: 0.08em;
          text-transform: uppercase;
        }

        .electronics-wheel-examples { display: flex; flex-wrap: wrap; gap: var(--space-xs); }
        .electronics-wheel-example {
          appearance: none;
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          color: var(--c-text);
          border-radius: 999px;
          padding: 0.4rem 0.85rem;
          font: inherit;
          font-size: 0.82rem;
          cursor: pointer;
          transition: border-color var(--transition-fast),
                      color var(--transition-fast),
                      background var(--transition-fast);
        }
        .electronics-wheel-example:hover,
        .electronics-wheel-example:focus-visible {
          border-color: var(--c-accent-border);
          color: var(--c-accent);
          background: var(--c-accent-bg);
          outline: none;
        }
        .electronics-wheel-actions { display: flex; gap: var(--space-sm); flex-wrap: wrap; }

/* ---- 7.3 — Section 2: Core Formulas & Laws ---- */
        .electronics-formula-card { gap: 0.6rem; }
        .electronics-formula-card__equation { line-height: 1.55; }
        .electronics-formula-card__equation .alt {
          display: block;
          font-size: 0.92rem;
          opacity: 0.8;
          margin-top: 0.2rem;
        }
        .electronics-formula-card__description,
        .electronics-formula-card__example {
          margin: 0;
          font-size: 0.88rem;
          line-height: 1.55;
          color: var(--c-text-muted);
        }
        .electronics-formula-card__example {
          color: var(--c-text);
          padding-top: 0.45rem;
          border-top: 1px solid var(--c-border-light);
        }
        .electronics-formula-card__example strong {
          display: inline-block;
          margin-right: 0.4rem;
          color: var(--c-accent);
          letter-spacing: 0.06em;
          text-transform: uppercase;
          font-size: 0.7rem;
          font-weight: 700;
        }
        .electronics-formula-card__try {
          align-self: flex-start;
          margin-top: auto;
        }
        .electronics-formula-card__try::after { content: " →"; }

        .electronics-formulas-notes {
          margin-top: var(--space-lg);
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius);
        }
        .electronics-formulas-notes > summary {
          padding: var(--space-md) var(--space-lg);
          font-weight: 600;
          color: var(--c-text);
          cursor: pointer;
          list-style: none;
          display: flex;
          align-items: center;
          gap: 0.6rem;
        }
        .electronics-formulas-notes > summary::marker { display: none; }
        .electronics-formulas-notes > summary::-webkit-details-marker { display: none; }
        .electronics-formulas-notes > summary::after {
          content: "▾";
          margin-left: auto;
          font-size: 0.8rem;
          color: var(--c-text-muted);
          transition: transform var(--transition-fast);
        }
        .electronics-formulas-notes[open] > summary::after { transform: rotate(180deg); }
        .electronics-formulas-notes[open] > summary { border-bottom: 1px solid var(--c-border-light); }
        .electronics-formulas-notes__body { padding: var(--space-md) var(--space-lg) var(--space-lg); }
        .electronics-formulas-notes__body ul { margin: 0; padding-left: 1.2rem; }
        .electronics-formulas-notes__body li {
          margin: 0.45rem 0;
          line-height: 1.6;
          color: var(--c-text);
          font-size: 0.92rem;
        }
        .electronics-formulas-notes__body li code,
        .electronics-formulas-notes__body li var {
          background: var(--c-code-bg);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          padding: 0.05rem 0.35rem;
          font-family: var(--f-mono);
          font-size: 0.85rem;
          font-style: normal;
          color: var(--c-accent);
        }

        @media print {
          .electronics-formula-card__try { display: none; }
          .electronics-formulas-notes { break-inside: avoid; }
          .electronics-formulas-notes[open] > summary,
          .electronics-formulas-notes__body { background: #fff; color: #111; }
        }

/* ---- 7.4 — Section 3 / Calculator 1: Ohm's Law / Power ---- */
        .electronics-ohms-grid {
          display: grid;
          grid-template-columns: minmax(0, 1fr);
          gap: var(--space-lg);
          align-items: start;
        }
        @media (min-width: 880px) {
          .electronics-ohms-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr); }
        }
        .electronics-ohms-fields { display: grid; gap: var(--space-md); min-width: 0; }
        .electronics-ohms-field {
          display: grid;
          grid-template-columns: minmax(7rem, 9rem) minmax(0, 1fr);
          gap: var(--space-sm);
          align-items: center;
        }
        .electronics-ohms-field__label {
          font-size: 0.85rem;
          color: var(--c-text);
          font-weight: 500;
          line-height: 1.2;
        }
        .electronics-ohms-field__label small {
          display: block;
          font-size: 0.72rem;
          color: var(--c-text-muted);
          margin-top: 0.1rem;
          font-weight: 400;
        }
        .electronics-ohms-field__row {
          display: grid;
          grid-template-columns: minmax(0, 1fr);
          gap: 0.45rem;
          min-width: 0;
        }
        .electronics-ohms-field--computed input[type="number"] {
          color: var(--c-accent);
          font-weight: 600;
        }
        .electronics-ohms-slider {
          appearance: none;
          -webkit-appearance: none;
          width: 100%;
          height: 18px;
          background: transparent;
          cursor: pointer;
        }
        .electronics-ohms-slider::-webkit-slider-runnable-track {
          height: 4px; background: var(--c-border); border-radius: 2px;
        }
        .electronics-ohms-slider::-moz-range-track {
          height: 4px; background: var(--c-border); border-radius: 2px;
        }
        .electronics-ohms-slider::-webkit-slider-thumb {
          -webkit-appearance: none;
          width: 14px; height: 14px;
          margin-top: -5px;
          border-radius: 50%;
          background: var(--c-accent);
          border: 2px solid var(--c-bg-alt);
          transition: box-shadow var(--transition-fast);
        }
        .electronics-ohms-slider::-moz-range-thumb {
          width: 14px; height: 14px;
          border-radius: 50%;
          background: var(--c-accent);
          border: 2px solid var(--c-bg-alt);
          transition: box-shadow var(--transition-fast);
        }
        .electronics-ohms-slider:focus-visible::-webkit-slider-thumb {
          box-shadow: 0 0 0 3px var(--c-accent-bg);
        }
        .electronics-ohms-slider:focus-visible::-moz-range-thumb {
          box-shadow: 0 0 0 3px var(--c-accent-bg);
        }

        .electronics-ohms-charts { display: grid; gap: var(--space-md); min-width: 0; }
        @media (min-width: 1280px) {
          .electronics-ohms-charts { grid-template-columns: 1fr 1fr; }
        }
        .electronics-ohms-chart-wrapper {
          position: relative;
          height: 240px;
          background: var(--c-bg-alt);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          padding: var(--space-sm);
        }
        .electronics-ohms-chart-label {
          margin: 0.25rem 0 0;
          text-align: center;
          font-size: 0.72rem;
          color: var(--c-text-muted);
          letter-spacing: 0.06em;
          text-transform: uppercase;
        }

        .electronics-ohms-result {
          font-family: var(--f-mono);
          font-size: 0.92rem;
          line-height: 1.6;
          font-variant-numeric: tabular-nums;
          padding: var(--space-sm) var(--space-md);
          background: var(--c-surface-alt);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius-sm);
          color: var(--c-text);
          overflow-wrap: anywhere;
        }
        .electronics-ohms-result--ok { border-color: var(--c-accent-border); }

        .electronics-ohms-warning {
          font-size: 0.85rem;
          padding: 0.6rem 0.9rem;
          border-radius: var(--border-radius-sm);
          background: rgba(245, 158, 11, 0.12);
          border: 1px solid rgba(245, 158, 11, 0.35);
          color: #fbbf24;
          line-height: 1.5;
        }
        [data-theme="light"] .electronics-ohms-warning { color: #b45309; }

        .electronics-ohms-actions { display: flex; flex-wrap: wrap; gap: var(--space-sm); }
        .electronics-ohms-actions button { font-size: 0.85rem; }

        @media print {
          .electronics-ohms-actions,
          .electronics-ohms-slider { display: none; }
        }

/* ---- 7.5 — Section 3 / Calculator 2: LED Resistor ---- */
            .electronics-led-grid {
              display: grid;
              grid-template-columns: minmax(0, 1fr);
              gap: var(--space-lg);
              align-items: start;
            }
            @media (min-width: 880px) {
              .electronics-led-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr); }
            }
            .electronics-led-chart-wrapper {
              position: relative;
              height: 240px;
              background: var(--c-bg-alt);
              border: 1px solid var(--c-border-light);
              border-radius: var(--border-radius-sm);
              padding: var(--space-sm);
            }
            .electronics-led-chart-label {
              margin: 0.25rem 0 0;
              text-align: center;
              font-size: 0.72rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
            }
            .electronics-led-eseries {
              display: grid;
              grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
              gap: var(--space-sm);
            }
            .electronics-led-eseries__pill {
              padding: 0.5rem 0.75rem;
              background: var(--c-surface-alt);
              border: 1px solid var(--c-border);
              border-radius: var(--border-radius-sm);
              display: flex;
              flex-direction: column;
              gap: 0.15rem;
              font-family: var(--f-mono);
              font-size: 0.92rem;
              font-variant-numeric: tabular-nums;
            }
            .electronics-led-eseries__pill small {
              font-family: var(--f-body);
              font-size: 0.7rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
              font-weight: 500;
            }
            .electronics-led-eseries__pill strong {
              color: var(--c-accent);
              font-weight: 600;
            }
            .electronics-led-eseries__pill--highlight {
              border-color: var(--c-accent-border);
              background: var(--c-accent-bg);
            }

/* ---- 7.6 — Section 3 / Calculator 3: Voltage Divider ---- */
            .electronics-divider-grid {
              display: grid;
              grid-template-columns: minmax(0, 1fr);
              gap: var(--space-lg);
              align-items: start;
            }
            @media (min-width: 880px) {
              .electronics-divider-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr); }
            }
            .electronics-divider-chart-wrapper {
              position: relative;
              height: 240px;
              background: var(--c-bg-alt);
              border: 1px solid var(--c-border-light);
              border-radius: var(--border-radius-sm);
              padding: var(--space-sm);
            }
            .electronics-divider-chart-label {
              margin: 0.25rem 0 0;
              text-align: center;
              font-size: 0.72rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
            }

/* ---- 7.7 — Section 3 / Calculator 4: Series / Parallel ---- */
            .electronics-sp-modes {
              display: flex;
              flex-wrap: wrap;
              gap: var(--space-md);
              margin-bottom: var(--space-md);
            }
            .electronics-sp-modes fieldset {
              border: 0; padding: 0; margin: 0;
              display: flex; flex-wrap: wrap; gap: 0.4rem;
            }
            .electronics-sp-modes legend {
              position: absolute;
              width: 1px; height: 1px;
              margin: -1px; padding: 0;
              overflow: hidden;
              clip: rect(0, 0, 0, 0);
              border: 0;
            }
            .electronics-sp-modes label {
              display: inline-flex;
              cursor: pointer;
              user-select: none;
            }
            .electronics-sp-modes input[type="radio"] {
              position: absolute;
              opacity: 0;
              pointer-events: none;
            }
            .electronics-sp-modes label > span {
              padding: 0.4rem 0.85rem;
              border: 1px solid var(--c-border);
              border-radius: 999px;
              background: var(--c-surface);
              color: var(--c-text-muted);
              font-size: 0.82rem;
              font-weight: 500;
              transition: background var(--transition-fast),
                          color var(--transition-fast),
                          border-color var(--transition-fast);
            }
            .electronics-sp-modes label:hover > span {
              border-color: var(--c-accent-border);
              color: var(--c-text);
            }
            .electronics-sp-modes input:checked + span {
              background: var(--c-accent-bg);
              color: var(--c-accent);
              border-color: var(--c-accent-border);
            }
            .electronics-sp-modes input:focus-visible + span {
              outline: 2px solid var(--c-accent);
              outline-offset: 2px;
            }

            .electronics-sp-grid {
              display: grid;
              grid-template-columns: minmax(0, 1fr);
              gap: var(--space-lg);
              align-items: start;
            }
            @media (min-width: 880px) {
              .electronics-sp-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr); }
            }
            .electronics-sp-rows {
              display: flex;
              flex-direction: column;
              gap: var(--space-sm);
            }
            .electronics-sp-row {
              display: grid;
              grid-template-columns: minmax(2.5rem, 3.25rem) minmax(0, 1fr) auto;
              gap: var(--space-sm);
              align-items: center;
            }
            .electronics-sp-row__label {
              font-family: var(--f-mono);
              color: var(--c-text);
              font-size: 0.92rem;
              font-variant-numeric: tabular-nums;
            }
            .electronics-sp-row__remove {
              appearance: none;
              background: transparent;
              border: 1px solid var(--c-border);
              border-radius: 50%;
              width: 1.75rem; height: 1.75rem;
              color: var(--c-text-muted);
              cursor: pointer;
              font-size: 1.1rem;
              line-height: 1;
              padding: 0;
              transition: color var(--transition-fast),
                          border-color var(--transition-fast);
            }
            .electronics-sp-row__remove:hover:not(:disabled) {
              color: #f87171;
              border-color: rgba(239, 68, 68, 0.5);
            }
            .electronics-sp-row__remove:disabled {
              opacity: 0.35;
              cursor: not-allowed;
            }
            .electronics-sp-add {
              appearance: none;
              background: transparent;
              border: 1px dashed var(--c-border);
              border-radius: var(--border-radius-sm);
              padding: 0.5rem 0.85rem;
              color: var(--c-text-muted);
              cursor: pointer;
              font: inherit;
              font-size: 0.85rem;
              align-self: flex-start;
              transition: border-color var(--transition-fast),
                          color var(--transition-fast);
            }
            .electronics-sp-add:hover:not(:disabled) {
              border-color: var(--c-accent-border);
              color: var(--c-accent);
            }
            .electronics-sp-add:disabled { opacity: 0.4; cursor: not-allowed; }

            .electronics-sp-chart-wrapper {
              position: relative;
              height: 260px;
              background: var(--c-bg-alt);
              border: 1px solid var(--c-border-light);
              border-radius: var(--border-radius-sm);
              padding: var(--space-sm);
            }
            .electronics-sp-chart-label {
              margin: 0.25rem 0 0;
              text-align: center;
              font-size: 0.72rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
            }
            .electronics-calculator__reset:disabled {
              opacity: 0.4; cursor: not-allowed;
            }

/* ---- 7.8 — Section 3 / Calculator 5: RC Timer ---- */
            .electronics-rc-grid {
              display: grid;
              grid-template-columns: minmax(0, 1fr);
              gap: var(--space-lg);
              align-items: start;
            }
            @media (min-width: 880px) {
              .electronics-rc-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr); }
            }
            .electronics-rc-stats {
              display: grid;
              grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
              gap: var(--space-sm);
              margin-bottom: var(--space-md);
            }
            .electronics-rc-stats__pill {
              padding: 0.5rem 0.75rem;
              background: var(--c-surface-alt);
              border: 1px solid var(--c-border);
              border-radius: var(--border-radius-sm);
              font-family: var(--f-mono);
              font-variant-numeric: tabular-nums;
              font-size: 0.92rem;
            }
            .electronics-rc-stats__pill small {
              display: block;
              font-family: var(--f-body);
              font-size: 0.7rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
              font-weight: 500;
              margin-bottom: 0.15rem;
            }
            .electronics-rc-stats__pill strong {
              color: var(--c-accent);
              font-weight: 600;
            }
            .electronics-rc-chart-wrapper {
              position: relative;
              height: 260px;
              background: var(--c-bg-alt);
              border: 1px solid var(--c-border-light);
              border-radius: var(--border-radius-sm);
              padding: var(--space-sm);
            }
            .electronics-rc-chart-label {
              margin: 0.25rem 0 0;
              text-align: center;
              font-size: 0.72rem;
              color: var(--c-text-muted);
              letter-spacing: 0.06em;
              text-transform: uppercase;
            }
            .electronics-rc-controls {
              display: flex;
              flex-wrap: wrap;
              gap: var(--space-sm);
              margin-top: var(--space-sm);
            }
            .electronics-rc-controls button {
              appearance: none;
              background: var(--c-surface);
              border: 1px solid var(--c-border);
              color: var(--c-text);
              border-radius: 999px;
              padding: 0.45rem 0.95rem;
              font: inherit;
              font-size: 0.85rem;
              font-weight: 500;
              cursor: pointer;
              transition: background var(--transition-fast),
                          color var(--transition-fast),
                          border-color var(--transition-fast);
            }
            .electronics-rc-controls button:hover {
              border-color: var(--c-accent-border);
              color: var(--c-accent);
            }
            .electronics-rc-controls button.is-active {
              background: var(--c-accent-bg);
              color: var(--c-accent);
              border-color: var(--c-accent-border);
            }
            @media print {
              .electronics-rc-controls { display: none; }
            }

/* ---- 7.8b — Section 3 / Calculator 6: Battery Charge & Capacity ----
   Reuses .electronics-sp-modes for the radio cluster, .electronics-rcd-presets
   for the preset pill row, .electronics-ohms-fields for the input grid, and
   .electronics-ohms-result for the live result region. Only the panel visibility
   toggle and the SOC progress bar are new. */
            .electronics-bat-panel[hidden] {
              display: none;
            }
            .electronics-bat-soc-bar {
              position: relative;
              margin: var(--space-md) 0 var(--space-sm);
              height: 1.6rem;
            }
            .electronics-bat-soc-bar__track {
              position: absolute;
              top: 0.6rem;
              left: 0; right: 0;
              height: 6px;
              background: var(--c-border);
              border-radius: 3px;
            }
            .electronics-bat-soc-bar__fill {
              position: absolute;
              top: 0.4rem;
              left: 0;
              width: 0;
              height: 1rem;
              background: var(--c-accent-bg);
              border: 1px solid var(--c-accent-border);
              border-radius: 4px;
              transition: left 0.2s ease, width 0.2s ease;
            }
            .electronics-bat-soc-bar__label {
              position: absolute;
              top: 1.6rem;
              font-size: 0.72rem;
              font-family: var(--f-mono);
              font-variant-numeric: tabular-nums;
              color: var(--c-text-muted);
              white-space: nowrap;
            }
            .electronics-bat-soc-bar__label--start { left: 0; }
            .electronics-bat-soc-bar__label--end   { right: 0; }
            @media print {
              .electronics-bat-soc-bar__fill { transition: none; }
            }

/* ---- 7.9 — Section 4: Visual Component Lab ---- */
        .electronics-rcd-bands {
          display: grid;
          grid-template-columns: repeat(auto-fit, minmax(82px, 1fr));
          gap: var(--space-sm);
          margin: var(--space-md) 0;
        }
        .electronics-rcd-band {
          display: flex;
          flex-direction: column;
          gap: 0.4rem;
          min-width: 0;
        }
        .electronics-rcd-band__legend {
          font-size: 0.7rem;
          color: var(--c-text-muted);
          text-align: center;
          letter-spacing: 0.06em;
          text-transform: uppercase;
          font-weight: 500;
        }
        .electronics-rcd-band__select {
          /* Deprecated: kept as a no-op for any cached HTML still in flight.
             The decoder now uses .electronics-rcd-swatch buttons instead. */
          display: none;
        }
        .electronics-rcd-band__palette {
          display: grid;
          grid-template-columns: repeat(auto-fit, minmax(2.4rem, 1fr));
          gap: 0.3rem;
          padding: 0.25rem;
          background: var(--c-bg-alt);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
        }
        .electronics-rcd-swatch {
          appearance: none;
          -webkit-appearance: none;
          display: inline-flex;
          align-items: center;
          justify-content: center;
          aspect-ratio: 1 / 1;
          min-height: 2.4rem;
          padding: 0;
          border: 2px solid rgba(0, 0, 0, 0.35);
          border-radius: var(--border-radius-sm);
          font: inherit;
          font-family: var(--f-mono);
          font-size: 0.7rem;
          font-weight: 700;
          font-variant-numeric: tabular-nums;
          line-height: 1;
          cursor: pointer;
          background-color: var(--swatch-bg, var(--c-surface-alt));
          color: var(--swatch-fg, var(--c-text));
          transition: transform var(--transition-fast),
                      box-shadow var(--transition-fast),
                      border-color var(--transition-fast);
        }
        .electronics-rcd-swatch:hover {
          transform: scale(1.06);
          box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
          z-index: 1;
        }
        .electronics-rcd-swatch:focus-visible {
          outline: none;
          box-shadow: 0 0 0 3px var(--c-accent-bg),
                      0 0 0 5px var(--c-accent-border);
          z-index: 2;
        }
        .electronics-rcd-swatch.is-active {
          transform: scale(1.10);
          border-color: var(--c-accent);
          box-shadow: 0 0 0 2px var(--c-bg-alt),
                      0 0 0 4px var(--c-accent),
                      inset 0 0 0 1px rgba(255, 255, 255, 0.35);
          z-index: 3;
        }
        .electronics-rcd-swatch.is-active:focus-visible {
          box-shadow: 0 0 0 2px var(--c-bg-alt),
                      0 0 0 4px var(--c-accent),
                      0 0 0 7px var(--c-accent-bg);
        }
        @media (prefers-reduced-motion: reduce) {
          .electronics-rcd-swatch { transition: none; }
          .electronics-rcd-swatch:hover,
          .electronics-rcd-swatch.is-active { transform: none; }
        }
        @media print {
          .electronics-rcd-swatch { transform: none !important; box-shadow: none !important; }
        }
        .electronics-rcd-band__caption {
          font-size: 0.78rem;
          color: var(--c-text-muted);
          text-align: center;
          font-family: var(--f-mono);
          font-variant-numeric: tabular-nums;
        }

        .electronics-rcd-result {
          display: flex;
          flex-wrap: wrap;
          align-items: baseline;
          gap: var(--space-md);
          padding: var(--space-md);
          background: var(--c-surface-alt);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius-sm);
          font-family: var(--f-mono);
          margin: var(--space-md) 0;
        }
        .electronics-rcd-result__value {
          font-size: 1.5rem;
          font-weight: 700;
          color: var(--c-accent);
          font-variant-numeric: tabular-nums;
        }
        .electronics-rcd-result__tolerance {
          font-size: 0.95rem;
          color: var(--c-text-muted);
          font-variant-numeric: tabular-nums;
        }
        .electronics-rcd-result__range {
          width: 100%;
          font-size: 0.82rem;
          color: var(--c-text-muted);
          font-variant-numeric: tabular-nums;
        }

        .electronics-rcd-tolerance-bar {
          position: relative;
          height: 3rem;
          margin: var(--space-md) 0 calc(var(--space-md) + 0.4rem);
        }
        .electronics-rcd-tolerance-bar__track {
          position: absolute;
          top: 1rem;
          left: 0; right: 0;
          height: 6px;
          background: var(--c-border);
          border-radius: 3px;
        }
        .electronics-rcd-tolerance-bar__fill {
          position: absolute;
          top: 0.6rem;
          height: 1.4rem;
          background: var(--c-accent-bg);
          border: 1px solid var(--c-accent-border);
          border-radius: 4px;
          transition: left 0.2s ease, width 0.2s ease;
        }
        .electronics-rcd-tolerance-bar__nominal {
          position: absolute;
          top: 0.4rem;
          width: 3px;
          height: 1.85rem;
          background: var(--c-accent);
          border-radius: 1px;
          left: 50%;
          transform: translateX(-50%);
        }
        .electronics-rcd-tolerance-bar__label {
          position: absolute;
          top: 2.1rem;
          font-size: 0.72rem;
          font-family: var(--f-mono);
          font-variant-numeric: tabular-nums;
          color: var(--c-text-muted);
          white-space: nowrap;
          transform: translateX(-50%);
        }
        .electronics-rcd-tolerance-bar__label--nominal {
          color: var(--c-accent);
          font-weight: 600;
          left: 50%;
        }
        .electronics-rcd-tolerance-bar__label--min { left: 0; transform: none; }
        .electronics-rcd-tolerance-bar__label--max { right: 0; left: auto; transform: none; text-align: right; }

        .electronics-rcd-chart-wrapper {
          position: relative;
          height: 220px;
          background: var(--c-bg-alt);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          padding: var(--space-sm);
          margin-bottom: var(--space-md);
        }

        /* E-series card */
        .electronics-eseries-tabs {
          display: flex; flex-wrap: wrap; gap: 0.4rem;
          margin-bottom: var(--space-md);
        }
        .electronics-eseries-tab {
          appearance: none;
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          color: var(--c-text-muted);
          border-radius: 999px;
          padding: 0.4rem 0.85rem;
          font: inherit;
          font-size: 0.82rem;
          font-weight: 500;
          cursor: pointer;
          transition: background var(--transition-fast),
                      color var(--transition-fast),
                      border-color var(--transition-fast);
        }
        .electronics-eseries-tab:hover {
          color: var(--c-text);
          border-color: var(--c-accent-border);
        }
        .electronics-eseries-tab.is-active {
          background: var(--c-accent-bg);
          color: var(--c-accent);
          border-color: var(--c-accent-border);
        }
        .electronics-eseries-tab:focus-visible {
          outline: 2px solid var(--c-accent);
          outline-offset: 2px;
        }
        .electronics-eseries-finder {
          display: flex; flex-wrap: wrap; gap: var(--space-sm);
          align-items: center;
          margin-bottom: var(--space-md);
        }
        .electronics-eseries-finder label {
          display: inline-flex; align-items: center; gap: 0.5rem;
          font-size: 0.85rem; color: var(--c-text-muted);
        }
        .electronics-eseries-finder input[type="number"] { width: 9rem; }
        .electronics-eseries-grid {
          /* Value-cloud polish (Batch 4): wider min-track and a touch
             more gap so popularity-tier sizing has room to breathe;
             extra inner padding on the cloud frame for visual rhythm. */
          display: grid;
          grid-template-columns: repeat(auto-fit, minmax(64px, 1fr));
          gap: 0.5rem;
          align-items: center;
          justify-items: center;
          max-height: 280px;
          overflow-y: auto;
          padding: 0.6rem;
          background: var(--c-bg-alt);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          margin-top: var(--space-sm);
        }
        .electronics-eseries-value {
          padding: 0.4rem 0.5rem;
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius-sm);
          font-family: var(--f-mono);
          font-size: 0.82rem;
          font-variant-numeric: tabular-nums;
          text-align: center;
          color: var(--c-text);
        }
        .electronics-eseries-value.is-closest {
          background: var(--c-accent-bg);
          color: var(--c-accent);
          border-color: var(--c-accent-border);
          font-weight: 700;
          box-shadow: 0 0 0 1px var(--c-accent-border);
        }
        .electronics-eseries-empty {
          text-align: center;
          padding: var(--space-md);
          color: var(--c-text-muted);
          font-size: 0.85rem;
        }

        @media print {
          .electronics-eseries-tabs,
          .electronics-eseries-finder { break-inside: avoid; }
          .electronics-eseries-grid { max-height: none; overflow: visible; }
        }

/* ---- 7.10 — Section 5: Circuit Design Guides ---- */
        .electronics-guides-controls {
          display: flex;
          flex-wrap: wrap;
          gap: var(--space-md);
          align-items: center;
          margin-bottom: var(--space-md);
        }
        .electronics-guides-tabs {
          display: flex; flex-wrap: wrap; gap: 0.4rem;
        }
        .electronics-guides-filter {
          appearance: none;
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          color: var(--c-text-muted);
          border-radius: 999px;
          padding: 0.4rem 0.85rem;
          font: inherit;
          font-size: 0.82rem;
          font-weight: 500;
          cursor: pointer;
          transition: background var(--transition-fast),
                      color var(--transition-fast),
                      border-color var(--transition-fast);
        }
        .electronics-guides-filter:hover {
          color: var(--c-text);
          border-color: var(--c-accent-border);
        }
        .electronics-guides-filter.is-active {
          background: var(--c-accent-bg);
          color: var(--c-accent);
          border-color: var(--c-accent-border);
        }
        .electronics-guides-filter:focus-visible {
          outline: 2px solid var(--c-accent);
          outline-offset: 2px;
        }
        .electronics-guides-search {
          position: relative;
          display: flex;
          align-items: center;
          gap: var(--space-sm);
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius);
          padding: 0.3rem 0.65rem;
          flex: 0 1 16rem;
          min-width: 0;
          transition: border-color var(--transition-fast),
                      box-shadow var(--transition-fast);
        }
        .electronics-guides-search:focus-within {
          border-color: var(--c-accent-border);
          box-shadow: 0 0 0 3px var(--c-accent-bg);
        }
        .electronics-guides-search input {
          flex: 1;
          background: transparent;
          border: 0;
          outline: 0;
          color: var(--c-text);
          font: inherit;
          font-size: 0.9rem;
          padding: 0.15rem 0;
          min-width: 0;
        }
        .electronics-guides-search input::placeholder { color: var(--c-text-faint); }
        .electronics-guides-search__count {
          font-size: 0.75rem;
          color: var(--c-text-faint);
          font-variant-numeric: tabular-nums;
          white-space: nowrap;
        }

        /* Tier-specific left-border tints (mirrors the .electronics-guide__tag
           palette without overriding .electronics-guide's default green). */
        .electronics-guide[data-tier="warning"] { border-left-color: #f59e0b; }
        .electronics-guide[data-tier="danger"]  { border-left-color: #ef4444; }
        .electronics-guide__example {
          margin: var(--space-sm) 0 0;
          padding-top: var(--space-sm);
          border-top: 1px solid var(--c-border-light);
          font-size: 0.85rem;
          color: var(--c-text-muted);
          line-height: 1.55;
        }
        .electronics-guide__example strong {
          display: inline-block;
          margin-right: 0.4rem;
          color: var(--c-accent);
          letter-spacing: 0.06em;
          text-transform: uppercase;
          font-size: 0.7rem;
          font-weight: 700;
        }
        .electronics-guide__body code {
          background: var(--c-code-bg);
          border: 1px solid var(--c-border-light);
          border-radius: var(--border-radius-sm);
          padding: 0.05rem 0.35rem;
          font-family: var(--f-mono);
          font-size: 0.85rem;
          color: var(--c-accent);
        }
        .electronics-guides-empty {
          text-align: center;
          padding: var(--space-xl);
          color: var(--c-text-muted);
          font-size: 0.95rem;
        }

        @media print {
          .electronics-guides-controls { display: none; }
          .electronics-guide { break-inside: avoid; }
        }

/* ---- 7.11 — Section 6: Reference Tables ---- */
        .electronics-tables-controls {
          display: flex;
          flex-wrap: wrap;
          gap: var(--space-md);
          align-items: center;
          margin-bottom: var(--space-md);
        }
        .electronics-tables-tabs { display: flex; flex-wrap: wrap; gap: 0.4rem; }
        .electronics-tables-tab {
          appearance: none;
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          color: var(--c-text-muted);
          border-radius: 999px;
          padding: 0.4rem 0.85rem;
          font: inherit;
          font-size: 0.82rem;
          font-weight: 500;
          cursor: pointer;
          transition: background var(--transition-fast),
                      color var(--transition-fast),
                      border-color var(--transition-fast);
        }
        .electronics-tables-tab:hover {
          color: var(--c-text);
          border-color: var(--c-accent-border);
        }
        .electronics-tables-tab.is-active {
          background: var(--c-accent-bg);
          color: var(--c-accent);
          border-color: var(--c-accent-border);
        }
        .electronics-tables-tab:focus-visible {
          outline: 2px solid var(--c-accent);
          outline-offset: 2px;
        }
        .electronics-tables-search {
          position: relative;
          display: flex;
          align-items: center;
          gap: var(--space-sm);
          background: var(--c-surface);
          border: 1px solid var(--c-border);
          border-radius: var(--border-radius);
          padding: 0.3rem 0.65rem;
          flex: 0 1 16rem;
          min-width: 0;
        }
        .electronics-tables-search:focus-within {
          border-color: var(--c-accent-border);
          box-shadow: 0 0 0 3px var(--c-accent-bg);
        }
        .electronics-tables-search input {
          flex: 1;
          background: transparent;
          border: 0;
          outline: 0;
          color: var(--c-text);
          font: inherit;
          font-size: 0.9rem;
          padding: 0.15rem 0;
          min-width: 0;
        }
        .electronics-tables-search input::placeholder { color: var(--c-text-faint); }
        .electronics-tables-search__count {
          font-size: 0.75rem;
          color: var(--c-text-faint);
          font-variant-numeric: tabular-nums;
          white-space: nowrap;
        }
        .electronics-tables-empty {
          text-align: center;
          padding: var(--space-xl);
          color: var(--c-text-muted);
          font-size: 0.95rem;
        }
        /* Inline color swatch used in the resistor color-code table. */
        .electronics-color-swatch {
          display: inline-flex;
          align-items: center;
          gap: 0.4rem;
        }
        .electronics-color-swatch__chip {
          width: 0.95rem;
          height: 0.95rem;
          border-radius: 3px;
          border: 1px solid rgba(0, 0, 0, 0.35);
          flex-shrink: 0;
        }
        @media print {
          .electronics-tables-controls { display: none; }
          .electronics-table-wrapper { display: block !important; break-inside: avoid; margin-bottom: var(--space-md); }
          .electronics-table-wrapper[hidden] { display: block !important; }
        }

/* ============================================================================
   SECTION 8 — Batch 8 delight & UX polish
   * Modal dialog (EF.confirmModal) — replaces window.confirm()
   * "?" help trigger in the hero + keyboard-shortcut overlay
   * Resistor-decoder common-values preset row
   * Floating Reset All — first-scroll pulse + mobile placement tweaks
   * Share-popup card (URL + QR code)
   ============================================================================ */

/* ---- 8.1 — Modal (EF.confirmModal) ---- */
.electronics-modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: rgba(0, 0, 0, 0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-md);
  backdrop-filter: blur(2px);
  -webkit-backdrop-filter: blur(2px);
  animation: electronics-modal-fade 140ms ease-out;
}
@keyframes electronics-modal-fade {
  from { opacity: 0; }
  to   { opacity: 1; }
}
.electronics-modal {
  background: var(--c-surface);
  color: var(--c-text);
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius);
  padding: var(--space-md) var(--space-lg);
  max-width: 32rem;
  width: 100%;
  box-shadow: 0 14px 40px var(--c-card-shadow);
  animation: electronics-modal-pop 160ms ease-out;
}
@keyframes electronics-modal-pop {
  from { opacity: 0; transform: translateY(8px) scale(0.98); }
  to   { opacity: 1; transform: none; }
}
.electronics-modal--alert {
  /* Warm-amber framing for destructive confirmations (Reset All). */
  background: rgba(245, 158, 11, 0.12);
  border-color: rgba(245, 158, 11, 0.35);
  border-left: 4px solid #f59e0b;
}
[data-theme="light"] .electronics-modal--alert {
  background: #fff8e1;
  border-color: rgba(180, 83, 9, 0.35);
  border-left-color: #d97706;
  color: #5c4500;
}
.electronics-modal__title {
  margin: 0 0 var(--space-sm);
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.3;
  color: var(--c-text);
}
.electronics-modal--alert .electronics-modal__title { color: #fbbf24; }
[data-theme="light"] .electronics-modal--alert .electronics-modal__title { color: #b45309; }
.electronics-modal__message {
  margin: 0 0 var(--space-md);
  line-height: 1.55;
  color: inherit;
}
.electronics-modal__body  { margin: 0 0 var(--space-md); color: inherit; }
.electronics-modal__actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--space-sm);
  flex-wrap: wrap;
  margin-top: var(--space-md);
}
.electronics-modal__btn { font-weight: 600; }
.electronics-modal__btn--primary {
  background: var(--c-accent-bg);
  color: var(--c-accent);
  border-color: var(--c-accent-border);
}
.electronics-modal__btn--danger {
  background: rgba(245, 158, 11, 0.18);
  color: #fbbf24;
  border-color: rgba(245, 158, 11, 0.55);
}
[data-theme="light"] .electronics-modal__btn--danger {
  background: #fff1d6;
  color: #b45309;
  border-color: rgba(180, 83, 9, 0.45);
}

/* Keyboard-shortcut list rendered inside the help modal. */
.electronics-shortcut-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 0.55rem var(--space-md);
  font-size: 0.92rem;
  line-height: 1.4;
}
.electronics-shortcut-list dt { font-weight: 600; }
.electronics-shortcut-list kbd {
  display: inline-block;
  min-width: 1.5rem;
  padding: 0.1rem 0.45rem;
  border: 1px solid var(--c-border);
  border-bottom-width: 2px;
  border-radius: var(--border-radius-sm);
  background: var(--c-surface-alt);
  color: var(--c-text);
  font-family: var(--f-mono);
  font-size: 0.82rem;
  font-variant-numeric: tabular-nums;
  text-align: center;
}
.electronics-shortcut-list kbd + kbd { margin-left: 0.25rem; }

/* ---- 8.2 — "?" help trigger pinned below the site top-bar ----
   Fixed (not absolute-in-hero) so it stays visible during scroll.
   At ≥1280 px the desktop right-rail TOC takes the right side, so flip
   the trigger to the left for that breakpoint — the mobile `≡` is
   hidden there so the left side is free. */
.electronics-help-trigger {
  position: fixed;
  top: calc(var(--header-height, 3.75rem) + 0.5rem);
  right: var(--space-md);
  z-index: 10;
  width: 2rem;
  height: 2rem;
  border-radius: 999px;
  border: 1px solid var(--c-border);
  background: var(--c-surface);
  color: var(--c-text-muted);
  font: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px var(--c-card-shadow);
  transition: color var(--transition-fast),
              border-color var(--transition-fast),
              transform var(--transition-fast);
}
@media (min-width: 1280px) {
  .electronics-help-trigger {
    right: auto;
    left: var(--space-md);
  }
}
.electronics-help-trigger:hover {
  color: var(--c-accent);
  border-color: var(--c-accent-border);
  transform: scale(1.05);
}
.electronics-help-trigger:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}
.electronics-hero { position: relative; }

/* ---- 8.2b — Mobile TOC trigger + drawer ----
   The desktop sticky aside (.electronics-toc) hides itself below
   1280 px; this trigger + drawer pair give those viewports a
   bottom-sheet equivalent so the section index isn't lost on mobile.
   Trigger sits opposite the help "?" so they don't collide. */
.electronics-toc-trigger {
  position: fixed;
  top: calc(var(--header-height, 3.75rem) + 0.5rem);
  left: var(--space-md);
  z-index: 10;
  width: 2rem;
  height: 2rem;
  border-radius: 999px;
  border: 1px solid var(--c-border);
  background: var(--c-surface);
  color: var(--c-text-muted);
  font: inherit;
  font-size: 1rem;
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px var(--c-card-shadow);
  transition: color var(--transition-fast),
              border-color var(--transition-fast),
              transform var(--transition-fast);
}
.electronics-toc-trigger:hover {
  color: var(--c-accent);
  border-color: var(--c-accent-border);
  transform: scale(1.05);
}
.electronics-toc-trigger:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}
@media (max-width: 1279px) {
  .electronics-toc-trigger:not([hidden]) { display: inline-flex; }
}

.electronics-toc-drawer {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  z-index: 70;
  display: flex;
  align-items: flex-end;
  justify-content: center;
}
.electronics-toc-drawer[hidden] { display: none; }
.electronics-toc-drawer__sheet {
  width: 100%;
  max-width: 32rem;
  max-height: 80vh;
  overflow-y: auto;
  background: var(--c-surface);
  color: var(--c-text);
  border: 1px solid var(--c-border);
  border-bottom: 0;
  border-top-left-radius: var(--border-radius);
  border-top-right-radius: var(--border-radius);
  padding: var(--space-md) var(--space-md) var(--space-lg);
  box-shadow: 0 -8px 24px var(--c-card-shadow);
}
.electronics-toc-drawer__title {
  margin: 0 0 var(--space-sm);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--c-text-muted);
  font-weight: 600;
}
.electronics-toc-drawer__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}
.electronics-toc-drawer__list a {
  display: block;
  padding: 0.65rem 0.6rem;
  border-left: 2px solid transparent;
  border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
  color: var(--c-text);
  text-decoration: none;
  transition: background var(--transition-fast),
              border-color var(--transition-fast),
              color var(--transition-fast);
}
.electronics-toc-drawer__list a:hover,
.electronics-toc-drawer__list a:focus-visible {
  color: var(--c-accent);
  background: var(--c-surface-alt);
  border-left-color: var(--c-accent);
  outline: none;
}
.electronics-toc-drawer__close {
  margin-top: var(--space-sm);
  appearance: none;
  background: transparent;
  border: 1px solid var(--c-border);
  border-radius: var(--border-radius-sm);
  padding: 0.5rem 0.9rem;
  color: var(--c-text);
  font: inherit;
  font-size: 0.85rem;
  cursor: pointer;
  width: 100%;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}
.electronics-toc-drawer__close:hover {
  color: var(--c-accent);
  border-color: var(--c-accent-border);
}
.electronics-toc-drawer__close:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}
@media (prefers-reduced-motion: no-preference) {
  .electronics-toc-drawer__sheet {
    animation: electronics-drawer-slide 220ms ease-out;
  }
  @keyframes electronics-drawer-slide {
    from { transform: translateY(100%); }
    to   { transform: translateY(0);    }
  }
}

/* ---- 8.3 — Resistor decoder common-values preset row ---- */
.electronics-rcd-presets {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0 0 var(--space-md);
  align-items: center;
}
.electronics-rcd-presets__label {
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--c-text-muted);
  margin-right: 0.25rem;
}
.electronics-rcd-presets__btn {
  appearance: none;
  background: var(--c-surface-alt);
  color: var(--c-text);
  border: 1px solid var(--c-border);
  border-radius: 999px;
  padding: 0.3rem 0.7rem;
  font: inherit;
  font-size: 0.82rem;
  font-family: var(--f-mono);
  font-variant-numeric: tabular-nums;
  cursor: pointer;
  transition: color var(--transition-fast),
              border-color var(--transition-fast),
              background var(--transition-fast);
}
.electronics-rcd-presets__btn:hover {
  color: var(--c-accent);
  border-color: var(--c-accent-border);
}
.electronics-rcd-presets__btn:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
}
.electronics-rcd-presets__btn.is-active {
  color: var(--c-accent);
  background: var(--c-accent-bg);
  border-color: var(--c-accent-border);
}

/* ---- 8.4 — Floating Reset All — pulse + mobile placement ---- */
@keyframes electronics-pulse {
  0%   { box-shadow: 0 6px 24px var(--c-card-shadow), 0 0 0 0   rgba(245, 158, 11, 0.55); }
  60%  { box-shadow: 0 6px 24px var(--c-card-shadow), 0 0 0 14px rgba(245, 158, 11, 0);   }
  100% { box-shadow: 0 6px 24px var(--c-card-shadow), 0 0 0 0   rgba(245, 158, 11, 0);   }
}
.electronics-floating-reset.is-pulsing {
  animation: electronics-pulse 1400ms ease-out 2;
}
@media (max-width: 720px) {
  .electronics-floating-reset {
    bottom: 1rem;
    right: 1rem;
    padding: 0.65rem 1.2rem;
    font-size: 0.95rem;
    box-shadow: 0 8px 28px var(--c-card-shadow);
  }
}
@media (prefers-reduced-motion: reduce) {
  .electronics-floating-reset.is-pulsing { animation: none; }
  .electronics-modal-backdrop, .electronics-modal { animation: none; }
}

/* ---- 8.5 — Print: hide volatile chrome ---- */
@media print {
  /* Final sweep: redundantly hide every dialog / overlay class for
     paper output. Several of these are also hidden by Section 7's
     print block above; restating them at the bottom keeps the print
     contract self-contained and survives selector-order accidents. */
  .electronics-help-trigger,
  .electronics-toc-trigger,
  .electronics-toc-drawer,
  .electronics-modal-backdrop,
  .electronics-modal,
  .electronics-floating-reset { display: none !important; }
  /* Belt-and-braces against the new is-stowed transform leaving a
     subtle translateY visible if the browser renders any animation
     during print preview. */
  .electronics-floating-reset.is-stowed { display: none !important; }
}