/* Decivia Engineering Design System — Precision Technical & Trade Tools */

:root {
  /* Engineering Blueprint & Technical Slate Palette */
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-alt: #f1f5f9;
  --surface-elevated: #ffffff;
  --text: #0f172a;          /* Deep industrial charcoal */
  --text-muted: #334155;    /* High-contrast secondary */
  --text-subtle: #64748b;   /* Metadata & labels */
  --border: #e2e8f0;        /* 1px clean technical hairline */
  --border-strong: #cbd5e1;
  --border-focus: #2563eb;

  /* Technical Blueprint Accent */
  --accent: #1d4ed8;        /* Drafting blueprint cobalt */
  --accent-hover: #1e40af;
  --accent-dark: #172554;
  --accent-contrast: #ffffff;
  --accent-light: #eff6ff;   /* Faint blueprint wash */
  --accent-soft: #dbeafe;
  --accent-focus: rgba(37, 99, 235, 0.16);

  /* Verified Status (Used strictly for passing validation) */
  --pass: #059669;
  --pass-bg: #ecfdf5;
  --pass-border: #a7f3d0;
  --pass-text: #065f46;

  /* Engineering Alert & Limit Warning */
  --warn-bg: #fffbeb;
  --warn-border: #fde68a;
  --warn-text: #92400e;
  --danger: #dc2626;
  --danger-bg: #fef2f2;
  --danger-border: #fecaca;
  --danger-text: #991b1b;

  --highlight-bg: #fef9c3;
  --highlight-bg-hover: #fef08a;
  --highlight-text: #713f12;

  --radius-lg: 8px;
  --radius: 6px;
  --radius-sm: 4px;

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2.5rem;
  --space-6: 3.5rem;
  --max-width: 1060px;

  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Inter", "Helvetica Neue", system-ui, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Menlo", "Consolas", "Liberation Mono", monospace;

  --shadow-xs: 0 1px 2px 0 rgba(15, 23, 42, 0.04);
  --shadow-sm: 0 1px 3px 0 rgba(15, 23, 42, 0.06), 0 1px 2px -1px rgba(15, 23, 42, 0.04);
  --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.07), 0 2px 4px -2px rgba(15, 23, 42, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.04);
  --ease: 140ms cubic-bezier(0.16, 1, 0.3, 1);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --bg: #0b0f17;          /* Carbon terminal background */
    --surface: #111827;     /* Slate-900 instruments */
    --surface-alt: #1e293b; /* Slate-800 */
    --surface-elevated: #1f293d;
    --text: #f8fafc;
    --text-muted: #cbd5e1;
    --text-subtle: #94a3b8;
    --border: #1e293b;
    --border-strong: #334155;
    --border-focus: #38bdf8;

    --accent: #38bdf8;      /* Electric CAD Cyan/Blue */
    --accent-hover: #7dd3fc;
    --accent-dark: #0284c7;
    --accent-contrast: #082f49;
    --accent-light: #082f49;
    --accent-soft: #0c4a6e;
    --accent-focus: rgba(56, 189, 248, 0.22);

    --pass: #34d399;
    --pass-bg: #064e3b;
    --pass-border: #059669;
    --pass-text: #a7f3d0;

    --warn-bg: #451a03;
    --warn-border: #78350f;
    --warn-text: #fde68a;

    --danger: #f87171;
    --danger-bg: #450a0a;
    --danger-border: #7f1d1d;
    --danger-text: #fecaca;

    --highlight-bg: #3d3408;
    --highlight-bg-hover: #4d420a;
    --highlight-text: #fef08a;

    --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.6);
    --shadow-md: 0 6px 12px 0 rgba(0, 0, 0, 0.65);
    --shadow-lg: 0 14px 28px -4px rgba(0, 0, 0, 0.75);
  }
}

:root[data-theme="dark"] {
  --bg: #0b0f17;
  --surface: #111827;
  --surface-alt: #1e293b;
  --surface-elevated: #1f293d;
  --text: #f8fafc;
  --text-muted: #cbd5e1;
  --text-subtle: #94a3b8;
  --border: #1e293b;
  --border-strong: #334155;
  --border-focus: #38bdf8;

  --accent: #38bdf8;
  --accent-hover: #7dd3fc;
  --accent-dark: #0284c7;
  --accent-contrast: #082f49;
  --accent-light: #082f49;
  --accent-soft: #0c4a6e;
  --accent-focus: rgba(56, 189, 248, 0.22);

  --pass: #34d399;
  --pass-bg: #064e3b;
  --pass-border: #059669;
  --pass-text: #a7f3d0;

  --warn-bg: #451a03;
  --warn-border: #78350f;
  --warn-text: #fde68a;

  --danger: #f87171;
  --danger-bg: #450a0a;
  --danger-border: #7f1d1d;
  --danger-text: #fecaca;

  --highlight-bg: #3d3408;
  --highlight-bg-hover: #4d420a;
  --highlight-text: #fef08a;

  --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
  --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.6);
  --shadow-md: 0 6px 12px 0 rgba(0, 0, 0, 0.65);
  --shadow-lg: 0 14px 28px -4px rgba(0, 0, 0, 0.75);
}

* { box-sizing: border-box; }

[hidden],
.feature-group[hidden],
[data-hidden="true"] {
  display: none !important;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  background-image: radial-gradient(var(--border) 1px, transparent 1px);
  background-size: 24px 24px;
  background-attachment: fixed;
}

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

a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

@media (prefers-reduced-motion: no-preference) {
  a, .btn, .field input, .field select, .feature-group, .mode-selector button,
  details.advanced > summary::after, .faq-list summary::after, .result-panel,
  .site-search input, .chip-btn {
    transition: background-color var(--ease), border-color var(--ease), color var(--ease),
      box-shadow var(--ease), transform var(--ease);
  }
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--text);
  color: var(--surface);
  padding: var(--space-2) var(--space-3);
  z-index: 100;
  font-weight: 600;
  font-size: 0.85rem;
  border-radius: 0 0 var(--radius-sm) 0;
  box-shadow: var(--shadow-md);
}
.skip-link:focus { left: 0; top: 0; }

/* Sticky Technical Header */
header.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  border-bottom: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: var(--shadow-xs);
}

:root[data-theme="dark"] header.site-header {
  background: rgba(17, 24, 39, 0.92);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) header.site-header {
    background: rgba(17, 24, 39, 0.92);
  }
}

.site-header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.75rem var(--space-3);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.site-brand-group {
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

/* Precision Reticle / Crosshair Brand Mark */
.brand-icon {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
  background: var(--surface-alt);
  border: 1px solid var(--border-strong);
  color: var(--accent);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.site-logo {
  font-weight: 800;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
  color: var(--text);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}
.site-logo:hover { color: var(--text); text-decoration: none; }
.site-logo span,
.site-logo span.accent {
  color: var(--accent);
}

.site-tagline {
  font-size: 0.8rem;
  color: var(--text-subtle);
  margin: 0;
  display: none;
}

@media (min-width: 680px) {
  .site-tagline {
    display: block;
    border-left: 1px solid var(--border);
    padding-left: 0.75rem;
  }
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  margin-left: auto;
}

.header-nav {
  display: none;
  align-items: center;
  gap: 0.85rem;
  margin-right: 0.5rem;
}

@media (min-width: 768px) {
  .header-nav { display: flex; }
}

.header-nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
}
.header-nav a:hover {
  color: var(--accent);
}

.theme-toggle {
  font: inherit;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.35rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-muted);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  box-shadow: var(--shadow-xs);
}
.theme-toggle:hover {
  border-color: var(--border-strong);
  color: var(--text);
  background: var(--surface-alt);
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-4) var(--space-3) var(--space-6);
}

/* Breadcrumbs */
.breadcrumb {
  font-size: 0.82rem;
  color: var(--text-subtle);
  margin: 0 0 var(--space-3);
}
.breadcrumb a { color: var(--text-subtle); text-decoration: none; }
.breadcrumb a:hover { color: var(--accent); text-decoration: underline; }
.breadcrumb ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
  margin: 0;
  padding: 0;
}
.breadcrumb li:not(:last-child)::after {
  content: "/";
  margin-left: 0.4rem;
  color: var(--border-strong);
}

/* Typographic Hierarchy */
h1 {
  font-size: 1.85rem;
  line-height: 1.25;
  letter-spacing: -0.025em;
  font-weight: 800;
  color: var(--text);
  margin: 0 0 0.5rem;
}

h2 {
  font-size: 1.25rem;
  letter-spacing: -0.015em;
  font-weight: 700;
  margin: var(--space-5) 0 var(--space-3);
  padding-left: 0.65rem;
  border-left: 3px solid var(--accent);
  color: var(--text);
}

h3 {
  font-size: 1.05rem;
  letter-spacing: -0.01em;
  font-weight: 600;
  margin: var(--space-4) 0 var(--space-2);
  color: var(--text);
}

p { margin: 0 0 var(--space-3); color: var(--text-muted); }
.lede {
  color: var(--text-muted);
  max-width: 68ch;
  font-size: 1.05rem;
  line-height: 1.55;
  margin-bottom: var(--space-4);
}

/* Homepage Hero Section */
.hero-section {
  padding: var(--space-4) 0 var(--space-4);
  border-bottom: 1px solid var(--border);
  margin-bottom: var(--space-4);
}

.hero-tech-badge,
.hero-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--surface-alt);
  border: 1px solid var(--border);
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.75rem;
}

.hero-tech-badge .status-dot,
.hero-pill .pulse-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
  flex-shrink: 0;
}

.hero-features-bar {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-3);
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: 1px solid var(--border);
}

.hero-feature-item {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.45;
}

.hero-feature-icon {
  width: 30px;
  height: 30px;
  border-radius: var(--radius-sm);
  background: var(--surface-alt);
  border: 1px solid var(--border);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
  flex-shrink: 0;
  margin-top: 1px;
}

/* Search Bar with Keyboard Shortcut */
.site-search-wrap {
  margin: var(--space-3) 0 var(--space-3);
}

.site-search-bar {
  position: relative;
  display: flex;
  align-items: center;
}

.site-search-icon {
  position: absolute;
  left: 0.9rem;
  color: var(--text-subtle);
  pointer-events: none;
  display: flex;
  align-items: center;
}

.site-search input {
  font: inherit;
  width: 100%;
  padding: 0.75rem 4.8rem 0.75rem 2.6rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-size: 0.95rem;
  box-shadow: var(--shadow-xs);
}

.site-search input:hover {
  border-color: var(--accent);
}

.site-search input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-focus);
  outline: none;
}

.search-clear-btn {
  position: absolute;
  right: 2.8rem;
  background: none;
  border: none;
  padding: 0.25rem;
  cursor: pointer;
  color: var(--text-subtle);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  transition: color var(--ease), background-color var(--ease);
}

.search-clear-btn:hover {
  color: var(--text);
  background: var(--surface-alt);
}

.search-kbd {
  position: absolute;
  right: 0.85rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--text-subtle);
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.15rem 0.35rem;
  pointer-events: none;
}

/* Professional Category Filter Tabs */
.filter-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin: var(--space-3) 0 var(--space-3);
  padding: 0.3rem;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  width: 100%;
  box-sizing: border-box;
}

.filter-tab {
  font: inherit;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.35rem 0.75rem;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  cursor: pointer;
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  transition: all var(--ease);
}

.filter-tab svg {
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  opacity: 0.75;
  transition: opacity var(--ease), color var(--ease);
}

.filter-tab .tab-badge {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 700;
  padding: 0.05rem 0.35rem;
  border-radius: 999px;
  background: var(--border);
  color: var(--text-subtle);
  transition: all var(--ease);
}

.filter-tab:hover {
  color: var(--text);
  background: var(--surface);
}

.filter-tab:hover svg {
  opacity: 1;
}

.filter-tab.active {
  background: var(--surface);
  color: var(--accent);
  border-color: var(--border);
  box-shadow: var(--shadow-xs);
}

.filter-tab.active svg {
  opacity: 1;
  color: var(--accent);
}

.filter-tab.active .tab-badge {
  background: var(--accent-soft);
  color: var(--accent);
}

:root[data-theme="dark"] .filter-tab.active {
  background: var(--surface-elevated);
}

/* Filter Status & Active Count Bar */
.filter-status-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  margin: var(--space-2) 0 var(--space-3);
  padding: 0.45rem 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}

.filter-status-text {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  font-weight: 500;
}

.filter-status-text strong {
  font-family: var(--font-mono);
  color: var(--text);
}

.filter-reset-btn {
  font: inherit;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.2rem 0.55rem;
  color: var(--accent);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  transition: all var(--ease);
}

.filter-reset-btn:hover {
  background: var(--accent-light);
  border-color: var(--accent-soft);
}

/* Empty Search / Filter State */
.no-results-panel {
  background: var(--surface);
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius);
  padding: var(--space-5) var(--space-4);
  text-align: center;
  margin: var(--space-4) 0;
}

.no-results-panel h3 {
  margin: 0.5rem 0 0.25rem;
  color: var(--text);
}

.no-results-panel p {
  color: var(--text-muted);
  font-size: 0.9rem;
  max-width: 48ch;
  margin: 0 auto 1rem;
}

/* Feature Groups / Categories Grid */
.feature-groups {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(310px, 1fr));
  gap: var(--space-3);
  margin: var(--space-4) 0;
}

.feature-group {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  padding: var(--space-4);
  box-shadow: var(--shadow-xs);
  display: flex;
  flex-direction: column;
  position: relative;
  transition: transform var(--ease), border-color var(--ease), box-shadow var(--ease);
}

.feature-group:hover {
  box-shadow: var(--shadow-sm);
  transform: translateY(-2px);
  border-color: var(--accent);
}

.feature-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.65rem;
}

/* Technical Schematic Emblem Icon */
.feature-icon-badge {
  width: 36px;
  height: 36px;
  border-radius: var(--radius);
  background: var(--surface-alt);
  color: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  border: 1px solid var(--border);
  transition: all var(--ease);
}

.feature-icon-badge svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

.feature-group:hover .feature-icon-badge {
  color: var(--accent);
  border-color: var(--accent-soft);
  background: var(--accent-light);
}

.feature-group h2 {
  margin: 0;
  font-size: 1.05rem;
  letter-spacing: -0.01em;
  border-left: none;
  padding-left: 0;
  color: var(--text);
}

.feature-group p {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: var(--space-3);
  flex-grow: 1;
  line-height: 1.5;
}

.feature-group .links {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  font-size: 0.88rem;
  padding-top: var(--space-3);
  border-top: 1px solid var(--border);
}

.feature-group .links a {
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--text-muted);
  padding: 0.15rem 0;
}

.feature-group .links a:hover {
  color: var(--accent);
  text-decoration: none;
}

.feature-group .links a.primary-link {
  font-weight: 700;
  color: var(--accent);
}

.feature-group .links a.primary-link::after {
  content: "→";
  transition: transform var(--ease);
}

.feature-group .links a.primary-link:hover::after {
  transform: translateX(3px);
}

/* Calculator Form & Parameter Inputs */
.calc-form {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-xs);
  padding: var(--space-4);
  margin: var(--space-3) 0 var(--space-4);
}

.form-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-3);
  padding-bottom: var(--space-2);
  border-bottom: 1px solid var(--border);
}

.form-header-title {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-subtle);
}

.input-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: var(--space-3);
  margin-bottom: var(--space-3);
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.field label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}

.field label span.hint {
  font-size: 0.75rem;
  font-weight: 400;
  color: var(--text-subtle);
}

.field .unit-row {
  display: flex;
  align-items: center;
  position: relative;
}

.field input,
.field select {
  font: inherit;
  font-family: var(--font);
  padding: 0.55rem 0.7rem;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  width: 100%;
  font-size: 0.92rem;
  box-shadow: var(--shadow-xs);
}

.field input[type="number"] {
  font-variant-numeric: tabular-nums;
}

.field input:hover,
.field select:hover {
  border-color: var(--accent);
}

.field input:focus,
.field select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-focus);
  outline: none;
}

.field .unit {
  position: absolute;
  right: 0.75rem;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-subtle);
  pointer-events: none;
  font-family: var(--font-mono);
}

.field .unit-select {
  width: auto;
  flex: 0 0 auto;
  font-size: 0.82rem;
  color: var(--text);
  padding: 0.55rem 0.5rem;
  margin-left: 0.35rem;
  border-radius: var(--radius-sm);
  background: var(--surface-alt);
  font-weight: 600;
}

/* Quick Preset Chips */
.preset-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem;
  margin-top: 0.25rem;
}

.chip-btn {
  font: inherit;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.15rem 0.45rem;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  color: var(--text-subtle);
  border-radius: var(--radius-sm);
  cursor: pointer;
  line-height: 1.3;
}

.chip-btn:hover {
  background: var(--accent-light);
  color: var(--accent);
  border-color: var(--accent-soft);
}

.field .error-msg {
  font-size: 0.78rem;
  color: var(--danger);
  min-height: 1.1em;
  font-weight: 500;
}

.field input[aria-invalid="true"] {
  border-color: var(--danger);
  background-color: var(--danger-bg);
}

/* Action Buttons */
.form-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: var(--space-2);
}

.btn {
  font: inherit;
  background: var(--accent);
  color: var(--accent-contrast);
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  padding: 0.6rem 1.35rem;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.92rem;
  box-shadow: var(--shadow-xs);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
}

.btn:hover {
  background: var(--accent-hover);
  box-shadow: var(--shadow-sm);
}

.btn:active {
  transform: translateY(0);
}

.btn.secondary {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border-strong);
  box-shadow: var(--shadow-xs);
}

.btn.secondary:hover {
  background: var(--surface-alt);
  border-color: var(--accent);
}

/* Result Panel — Precision Instrument Readout */
.result-panel {
  background: var(--surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  padding: var(--space-4);
  margin-top: var(--space-4);
  box-shadow: var(--shadow-sm);
  position: relative;
  border-left: 4px solid var(--accent);
}

.result-panel[hidden] { display: none !important; }

.result-top-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.65rem;
  padding-bottom: 0.45rem;
  border-bottom: 1px solid var(--border);
}

.result-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-sm);
  background: var(--accent-light);
  color: var(--accent);
  border: 1px solid var(--accent-soft);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.result-badge.pass {
  background: var(--pass-bg);
  color: var(--pass-text);
  border-color: var(--pass-border);
}

.result-badge.warning {
  background: var(--warn-bg);
  color: var(--warn-text);
  border-color: var(--warn-border);
}

.copy-btn {
  font: inherit;
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.25rem 0.55rem;
  color: var(--text-muted);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

.copy-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--surface);
}

.result-main {
  font-size: 1.65rem;
  font-weight: 800;
  letter-spacing: -0.025em;
  color: var(--text);
  margin: 0.25rem 0 0.85rem;
  line-height: 1.25;
  font-variant-numeric: tabular-nums;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
  gap: var(--space-2) var(--space-3);
  margin-top: var(--space-3);
}

.result-item {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.85rem;
}

.result-item .label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-subtle);
  display: block;
  margin-bottom: 0.2rem;
}

.result-item .value {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

/* Callouts & Technical Advisory Notices */
.notice {
  border: 1px solid var(--warn-border);
  background: var(--warn-bg);
  border-radius: var(--radius-sm);
  padding: 0.75rem 0.95rem;
  font-size: 0.85rem;
  margin: var(--space-4) 0;
  color: var(--warn-text);
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  line-height: 1.5;
}

.notice[hidden] {
  display: none !important;
}

/* Mode Selector (Shape Tabs, etc.) */
.mode-selector {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.25rem;
  margin: var(--space-2) 0 var(--space-4);
  background: var(--surface-alt);
  padding: 0.25rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  max-width: 100%;
}

.mode-selector button {
  font: inherit;
  font-size: 0.82rem;
  font-weight: 600;
  padding: 0.35rem 0.85rem;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--ease);
}

.mode-selector button:hover {
  color: var(--text);
  background: var(--surface);
}

.mode-selector button[aria-pressed="true"] {
  background: var(--surface);
  color: var(--accent);
  border-color: var(--border);
  box-shadow: var(--shadow-xs);
}

:root[data-theme="dark"] .mode-selector button[aria-pressed="true"] {
  background: var(--surface-elevated);
  color: var(--accent);
}

[data-mode-panel][hidden] {
  display: none !important;
}

/* Unit System Selector (Single option per tool to set Imperial vs Metric) */
.unit-system-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.65rem;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.45rem 0.75rem;
  margin: var(--space-2) 0 var(--space-3);
}

.unit-system-legend {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-subtle);
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.unit-system-legend svg {
  width: 14px;
  height: 14px;
  color: var(--accent);
}

.unit-system-options {
  display: inline-flex;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 2px;
  gap: 2px;
}

.unit-system-btn {
  font: inherit;
  font-size: 0.78rem;
  font-weight: 600;
  padding: 0.3rem 0.7rem;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  border-radius: calc(var(--radius-sm) - 2px);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  transition: all var(--ease);
}

.unit-system-btn svg {
  width: 13px;
  height: 13px;
  opacity: 0.7;
}

.unit-system-btn:hover {
  color: var(--text);
}

.unit-system-btn[aria-pressed="true"],
.unit-system-btn.active {
  background: var(--accent);
  color: var(--accent-contrast);
  border-color: var(--accent);
  box-shadow: var(--shadow-xs);
}

.unit-system-btn[aria-pressed="true"] svg,
.unit-system-btn.active svg {
  opacity: 1;
  stroke: currentColor;
}

/* Static and Dynamic Unit Badges inside Input Fields */
.input-with-unit {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
}

.input-with-unit input {
  padding-right: 3.4rem !important;
}

.input-with-unit .unit-badge {
  position: absolute;
  right: 0.6rem;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-subtle);
  background: var(--surface-alt);
  border: 1px solid var(--border);
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  pointer-events: none;
  line-height: 1.2;
}

/* Range input slider */
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 5px;
  background: var(--border-strong);
  border-radius: 3px;
  outline: none;
  margin: 0.5rem 0;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: 2px solid var(--surface);
  box-shadow: var(--shadow-sm);
  transition: transform var(--ease);
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.15);
}

input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: 2px solid var(--surface);
  box-shadow: var(--shadow-sm);
}

/* Advanced Options Accordion */
details.advanced {
  margin: var(--space-4) 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  padding: 0;
  box-shadow: var(--shadow-xs);
  overflow: hidden;
}

details.advanced > summary {
  cursor: pointer;
  padding: 0.75rem 1rem;
  font-weight: 600;
  font-size: 0.9rem;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--text);
  user-select: none;
}

details.advanced > summary::-webkit-details-marker { display: none; }

details.advanced > summary::after {
  content: "▾";
  font-size: 1rem;
  color: var(--text-subtle);
  transition: transform var(--ease);
}

details.advanced[open] > summary {
  border-bottom: 1px solid var(--border);
  background: var(--surface-alt);
}

details.advanced[open] > summary::after {
  transform: rotate(180deg);
  color: var(--accent);
}

details.advanced .advanced-body {
  padding: var(--space-4);
}

/* Technical Specification Tables */
.table-scroll {
  overflow-x: auto;
  margin: var(--space-3) 0 var(--space-4);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-xs);
  background: var(--surface);
}

table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.88rem;
  font-variant-numeric: tabular-nums;
}

caption {
  text-align: left;
  font-weight: 700;
  font-size: 0.82rem;
  padding: 0.65rem 0.85rem;
  background: var(--surface-alt);
  border-bottom: 1px solid var(--border);
  color: var(--text);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

th, td {
  border-bottom: 1px solid var(--border);
  padding: 0.55rem 0.85rem;
  text-align: left;
  white-space: nowrap;
}

th:not(:last-child), td:not(:last-child) {
  border-right: 1px solid var(--border);
}

thead th {
  background: var(--surface-alt);
  font-weight: 700;
  color: var(--text);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

tbody tr:nth-child(even) {
  background: rgba(0, 0, 0, 0.015);
}

:root[data-theme="dark"] tbody tr:nth-child(even) {
  background: rgba(255, 255, 255, 0.02);
}

tbody tr:hover td {
  background: var(--accent-light);
}

tr.highlight td {
  background: var(--highlight-bg) !important;
  color: var(--highlight-text);
  font-weight: 700;
  position: relative;
}

tr.highlight td:first-child {
  box-shadow: inset 3px 0 0 var(--accent);
}

tr.highlight:hover td {
  background: var(--highlight-bg-hover) !important;
}

tbody tr:last-child td {
  border-bottom: none;
}

/* Technical Charts */
.chart-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-3);
  margin: var(--space-3) 0 var(--space-4);
  box-shadow: var(--shadow-xs);
  position: relative;
}

canvas.chart-canvas {
  width: 100%;
  height: 220px;
  display: block;
}

/* Technical FAQ / Reference Notes */
.faq-list {
  margin: var(--space-3) 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  overflow: hidden;
  box-shadow: var(--shadow-xs);
}

.faq-list details {
  border-bottom: 1px solid var(--border);
  padding: 0;
}

.faq-list details:last-child {
  border-bottom: none;
}

.faq-list summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  list-style: none;
  padding: 0.85rem 1.15rem;
  color: var(--text);
  display: flex;
  align-items: center;
  justify-content: space-between;
  user-select: none;
}

.faq-list summary::-webkit-details-marker { display: none; }

.faq-list summary::after {
  content: "+";
  font-size: 1.1rem;
  font-weight: 400;
  color: var(--text-subtle);
  transition: transform var(--ease);
}

.faq-list details[open] summary::after {
  content: "−";
  color: var(--accent);
}

.faq-list details[open] summary {
  background: var(--surface-alt);
  border-bottom: 1px solid var(--border);
}

.faq-list details p {
  padding: 0.85rem 1.15rem;
  margin: 0;
  color: var(--text-muted);
  line-height: 1.55;
}

/* Related Tools */
.related-tools {
  list-style: none;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-3);
  margin: var(--space-3) 0;
}

.related-tools li {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.75rem 0.95rem;
  box-shadow: var(--shadow-xs);
  transition: border-color var(--ease);
}

.related-tools li:hover {
  border-color: var(--accent);
}

.related-tools a {
  font-weight: 700;
  text-decoration: none;
  display: inline-block;
  margin-bottom: 0.2rem;
}

.related-tools a:hover {
  text-decoration: underline;
}

/* Site Footer */
footer.site-footer {
  border-top: 1px solid var(--border);
  margin-top: var(--space-6);
  padding: var(--space-5) var(--space-3);
  background: var(--surface);
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-subtle);
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.85rem;
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1.15rem;
  font-size: 0.82rem;
}

.footer-nav a {
  color: var(--text-subtle);
  text-decoration: none;
}
.footer-nav a:hover {
  color: var(--accent);
  text-decoration: underline;
}

/* Toast alert for copy action */
.toast-msg {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  background: var(--text);
  color: var(--surface);
  padding: 0.55rem 0.9rem;
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  font-weight: 600;
  box-shadow: var(--shadow-lg);
  z-index: 100;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 160ms ease, transform 160ms ease;
  pointer-events: none;
}

.toast-msg.show {
  opacity: 1;
  transform: translateY(0);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (max-width: 640px) {
  h1 { font-size: 1.55rem; }
  .result-main { font-size: 1.3rem; }
  .calc-form { padding: var(--space-3); }
  .feature-groups { grid-template-columns: 1fr; }
  .result-grid { grid-template-columns: 1fr 1fr; }
}