/* ==========================================================================
   TIP CALCULATOR - MAIN STYLESHEET
   Design System:
   Dominant (60%): #F8F9FA (Off-White / Light Gray)
   Secondary (30%): #1E293B (Deep Slate Blue)
   Accent (10%): #FF6B6B (Vibrant Coral)
   Typography: Poppins (Google Fonts)
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. CSS Custom Properties / Design Tokens
   -------------------------------------------------------------------------- */
:root {
  /* Brand Palette - Default Light */
  --color-bg: #F8F9FA;
  --color-surface: #FFFFFF;
  --color-surface-subtle: #F1F5F9;
  --color-surface-hover: #E2E8F0;
  
  --color-text-primary: #1E293B;
  --color-text-secondary: #475569;
  --color-text-muted: #64748B;
  --color-text-inverse: #FFFFFF;

  --color-border: #E2E8F0;
  --color-border-hover: #CBD5E1;
  --color-border-focus: #1E293B;

  --color-accent: #FF6B6B;
  --color-accent-hover: #FA5252;
  --color-accent-active: #E03131;
  --color-accent-subtle: #FFF5F5;
  --color-accent-ring: rgba(255, 107, 107, 0.25);

  --color-success: #10B981;
  --color-success-subtle: #ECFDF5;
  --color-error: #EF4444;
  --color-error-subtle: #FEF2F2;

  /* Typography */
  --font-family: 'Poppins', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --base-font-size: 16px;

  /* Spacing Scale */
  --space-1: 0.25rem;   /* 4px */
  --space-2: 0.5rem;    /* 8px */
  --space-3: 0.75rem;   /* 12px */
  --space-4: 1rem;      /* 16px */
  --space-5: 1.25rem;   /* 20px */
  --space-6: 1.5rem;    /* 24px */
  --space-8: 2rem;      /* 32px */
  --space-10: 2.5rem;   /* 40px */
  --space-12: 3rem;     /* 48px */
  --space-16: 4rem;     /* 64px */

  /* Border Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 26px;
  --radius-full: 9999px;

  /* Shadows (Subtle, clean, professional) */
  --shadow-xs: 0 1px 2px 0 rgba(15, 23, 42, 0.05);
  --shadow-sm: 0 1px 3px 0 rgba(15, 23, 42, 0.08), 0 1px 2px -1px rgba(15, 23, 42, 0.08);
  --shadow-md: 0 4px 12px -2px rgba(15, 23, 42, 0.08), 0 2px 6px -2px rgba(15, 23, 42, 0.05);
  --shadow-lg: 0 12px 24px -4px rgba(15, 23, 42, 0.1), 0 6px 12px -4px rgba(15, 23, 42, 0.06);
  --shadow-card: 0 16px 36px -6px rgba(30, 41, 59, 0.09);

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 220ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 300ms cubic-bezier(0.4, 0, 0.2, 1);

  /* Layout */
  --container-max-width: 1240px;
  --container-calculator: 980px;
  --container-narrow: 780px;
}

/* --------------------------------------------------------------------------
   Themes (Dark, OLED Black, Warm Sepia, Cyber Dark)
   -------------------------------------------------------------------------- */
[data-theme="dark"] {
  --color-bg: #0F172A;
  --color-surface: #1E293B;
  --color-surface-subtle: #334155;
  --color-surface-hover: #475569;

  --color-text-primary: #F8FAFC;
  --color-text-secondary: #CBD5E1;
  --color-text-muted: #94A3B8;
  --color-text-inverse: #0F172A;

  --color-border: #334155;
  --color-border-hover: #475569;
  --color-border-focus: #F8FAFC;

  --color-accent-subtle: rgba(255, 107, 107, 0.15);
  --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 12px -2px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 24px -4px rgba(0, 0, 0, 0.5);
  --shadow-card: 0 16px 36px -6px rgba(0, 0, 0, 0.5);
}

[data-theme="oled"] {
  --color-bg: #000000;
  --color-surface: #111111;
  --color-surface-subtle: #1C1C1E;
  --color-surface-hover: #2C2C2E;

  --color-text-primary: #FFFFFF;
  --color-text-secondary: #D1D1D6;
  --color-text-muted: #8E8E93;
  --color-text-inverse: #000000;

  --color-border: #2C2C2E;
  --color-border-hover: #3A3A3C;
  --color-border-focus: #FFFFFF;

  --color-accent-subtle: rgba(255, 107, 107, 0.2);
  --shadow-xs: 0 0 0 1px #2C2C2E;
  --shadow-sm: 0 0 0 1px #2C2C2E;
  --shadow-md: 0 4px 16px rgba(0,0,0,0.8), 0 0 0 1px #2C2C2E;
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.9), 0 0 0 1px #3A3A3C;
  --shadow-card: 0 12px 36px rgba(0,0,0,0.95), 0 0 0 1px #2C2C2E;
}

[data-theme="sepia"] {
  --color-bg: #F4EEDD;
  --color-surface: #FCF8EE;
  --color-surface-subtle: #E9DFCE;
  --color-surface-hover: #DDD1BC;

  --color-text-primary: #2D2319;
  --color-text-secondary: #584A3B;
  --color-text-muted: #847462;
  --color-text-inverse: #FCF8EE;

  --color-border: #D8CBB6;
  --color-border-hover: #C5B69F;
  --color-border-focus: #2D2319;

  --color-accent: #C25E00;
  --color-accent-hover: #AA5200;
  --color-accent-active: #8C4300;
  --color-accent-subtle: rgba(194, 94, 0, 0.12);
  --color-accent-ring: rgba(194, 94, 0, 0.25);
}

/* --------------------------------------------------------------------------
   Accents (Coral, Emerald, Indigo, Violet, Amber, Cyan)
   -------------------------------------------------------------------------- */
[data-accent="coral"] {
  --color-accent: #FF6B6B;
  --color-accent-hover: #FA5252;
  --color-accent-active: #E03131;
  --color-accent-subtle: rgba(255, 107, 107, 0.14);
  --color-accent-ring: rgba(255, 107, 107, 0.25);
}

[data-accent="emerald"] {
  --color-accent: #10B981;
  --color-accent-hover: #059669;
  --color-accent-active: #047857;
  --color-accent-subtle: rgba(16, 185, 129, 0.14);
  --color-accent-ring: rgba(16, 185, 129, 0.25);
}

[data-accent="indigo"] {
  --color-accent: #6366F1;
  --color-accent-hover: #4F46E5;
  --color-accent-active: #4338CA;
  --color-accent-subtle: rgba(99, 102, 241, 0.14);
  --color-accent-ring: rgba(99, 102, 241, 0.25);
}

[data-accent="violet"] {
  --color-accent: #8B5CF6;
  --color-accent-hover: #7C3AED;
  --color-accent-active: #6D28D9;
  --color-accent-subtle: rgba(139, 92, 246, 0.14);
  --color-accent-ring: rgba(139, 92, 246, 0.25);
}

[data-accent="amber"] {
  --color-accent: #F59E0B;
  --color-accent-hover: #D97706;
  --color-accent-active: #B45309;
  --color-accent-subtle: rgba(245, 158, 11, 0.15);
  --color-accent-ring: rgba(245, 158, 11, 0.25);
}

[data-accent="cyan"] {
  --color-accent: #06B6D4;
  --color-accent-hover: #0891B2;
  --color-accent-active: #0E7490;
  --color-accent-subtle: rgba(6, 182, 212, 0.14);
  --color-accent-ring: rgba(6, 182, 212, 0.25);
}

/* --------------------------------------------------------------------------
   Font Scaling Preferences
   -------------------------------------------------------------------------- */
[data-font-size="compact"] {
  --base-font-size: 14px;
}

[data-font-size="normal"] {
  --base-font-size: 16px;
}

[data-font-size="large"] {
  --base-font-size: 18px;
}

/* --------------------------------------------------------------------------
   2. Reset & Base Styles
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--font-family);
  font-size: var(--base-font-size, 16px);
  line-height: 1.5;
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
  transition: background-color var(--transition-smooth), color var(--transition-smooth);
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  background-color: var(--color-bg);
}

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

a {
  color: var(--color-text-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-accent);
}

button, input, select, textarea {
  font-family: inherit;
  font-size: 1rem;
  color: inherit;
  border: none;
  background: none;
}

button {
  cursor: pointer;
}

/* Accessibility Focus States */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* Skip link for keyboard users */
.skip-link {
  position: absolute;
  top: -40px;
  left: 1rem;
  background: var(--color-accent);
  color: var(--color-text-inverse);
  padding: var(--space-2) var(--space-4);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-sm);
  z-index: 1000;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 1rem;
}

/* --------------------------------------------------------------------------
   3. Typography
   -------------------------------------------------------------------------- */
h1, h2, h3, h4 {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-bold);
  line-height: 1.25;
}

h1 {
  font-size: clamp(2rem, 3.5vw + 1rem, 2.75rem);
  letter-spacing: -0.025em;
}

h2 {
  font-size: clamp(1.4rem, 2vw + 0.8rem, 1.95rem);
  letter-spacing: -0.015em;
  margin-bottom: var(--space-4);
}

h3 {
  font-size: clamp(1.15rem, 1.2vw + 0.75rem, 1.35rem);
  margin-bottom: var(--space-2);
}

p {
  color: var(--color-text-secondary);
  line-height: 1.65;
  margin-bottom: var(--space-4);
}

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

.text-accent {
  color: var(--color-accent);
}

/* Eyebrow badge */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.75rem;
  font-weight: var(--font-weight-bold);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent);
  background-color: var(--color-accent-subtle);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-3);
}

/* --------------------------------------------------------------------------
   4. Layout Containers
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-4);
  padding-right: var(--space-4);
}

.container-calculator {
  max-width: var(--container-calculator);
}

.container-narrow {
  max-width: var(--container-narrow);
}

.main-content {
  flex: 1 0 auto;
}

/* --------------------------------------------------------------------------
   5. Site Header & Navigation
   -------------------------------------------------------------------------- */
.site-header {
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-xs);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: var(--font-weight-bold);
  font-size: 1.25rem;
  color: var(--color-text-primary);
  text-decoration: none;
}

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

.brand-logo span span {
  color: var(--color-accent);
}

.nav-desktop {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-list {
  display: flex;
  align-items: center;
  gap: var(--space-6);
  list-style: none;
}

.nav-link {
  font-weight: var(--font-weight-medium);
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  padding: var(--space-2) 0;
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-text-primary);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--color-accent);
  border-radius: var(--radius-full);
}

/* Header Action CTA */
.header-cta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0.65rem 1.25rem;
  font-size: 0.95rem;
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  text-decoration: none;
  border: 1px solid transparent;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--color-accent);
  color: var(--color-text-inverse);
  box-shadow: 0 2px 4px rgba(255, 107, 107, 0.2);
}

.btn-primary:hover {
  background-color: var(--color-accent-hover);
  color: var(--color-text-inverse);
  transform: translateY(-1px);
  box-shadow: 0 4px 8px rgba(255, 107, 107, 0.25);
}

.btn-primary:active {
  background-color: var(--color-accent-active);
  transform: translateY(0);
}

.btn-secondary {
  background-color: var(--color-surface);
  color: var(--color-text-primary);
  border-color: var(--color-border);
}

.btn-secondary:hover {
  background-color: var(--color-surface-subtle);
  border-color: var(--color-border-hover);
  color: var(--color-text-primary);
}

.btn-ghost {
  background-color: transparent;
  color: var(--color-text-secondary);
}

.btn-ghost:hover {
  background-color: var(--color-surface-subtle);
  color: var(--color-text-primary);
}

.btn-sm {
  padding: 0.4rem 0.75rem;
  font-size: 0.85rem;
}

/* Mobile Hamburger Toggle */
.menu-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-sm);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border);
  background-color: var(--color-surface);
}

.menu-toggle:hover {
  background-color: var(--color-surface-subtle);
}

/* Mobile Drawer Overlay */
.mobile-nav-drawer {
  position: fixed;
  inset: 0;
  background-color: rgba(15, 23, 42, 0.5);
  backdrop-filter: blur(4px);
  z-index: 200;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-base), visibility var(--transition-base);
}

.mobile-nav-drawer.open {
  opacity: 1;
  visibility: visible;
}

.mobile-nav-panel {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 290px;
  max-width: 85vw;
  background-color: var(--color-surface);
  box-shadow: var(--shadow-card);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  transform: translateX(100%);
  transition: transform var(--transition-base);
}

.mobile-nav-drawer.open .mobile-nav-panel {
  transform: translateX(0);
}

.mobile-nav-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
}

.close-menu-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
}

.close-menu-btn:hover {
  color: var(--color-text-primary);
  background-color: var(--color-surface-subtle);
}

.mobile-nav-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.mobile-nav-link {
  display: block;
  padding: var(--space-3) var(--space-4);
  font-weight: var(--font-weight-medium);
  font-size: 1.05rem;
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
}

.mobile-nav-link:hover,
.mobile-nav-link.active {
  background-color: var(--color-accent-subtle);
  color: var(--color-accent);
}

.mobile-nav-footer {
  margin-top: auto;
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border);
}

/* --------------------------------------------------------------------------
   6. Hero Section
   -------------------------------------------------------------------------- */
.hero-section {
  padding: var(--space-10) 0 var(--space-8);
  text-align: center;
}

.hero-content {
  max-width: 720px;
  margin: 0 auto var(--space-8);
}

.hero-title {
  font-size: 2.75rem;
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
  letter-spacing: -0.025em;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-6);
  line-height: 1.6;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-4);
  flex-wrap: wrap;
}

/* --------------------------------------------------------------------------
   7. Information & Content Sections
   -------------------------------------------------------------------------- */
.info-section {
  padding: var(--space-12) 0;
}

.info-section:nth-of-type(even) {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

.section-header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto var(--space-10);
}

.section-title {
  font-size: 2rem;
  color: var(--color-text-primary);
  margin-bottom: var(--space-3);
}

.section-description {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-6);
}

.card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-xs);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-border-hover);
}

.card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background-color: var(--color-accent-subtle);
  color: var(--color-accent);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-4);
}

.card-title {
  font-size: 1.15rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-2);
}

.card-text {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  margin-bottom: 0;
}

/* Formula Showcase Box */
.formula-box {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-accent);
  border-radius: var(--radius-md);
  padding: var(--space-5) var(--space-6);
  margin: var(--space-6) 0;
}

.formula-box code {
  font-family: 'Courier New', Courier, monospace;
  font-weight: var(--font-weight-bold);
  font-size: 1.1rem;
  color: var(--color-text-primary);
  display: block;
  margin-bottom: var(--space-2);
}

/* Table Showcase */
.table-responsive {
  width: 100%;
  overflow-x: auto;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background-color: var(--color-surface);
  box-shadow: var(--shadow-xs);
  margin: var(--space-6) 0;
}

.content-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.95rem;
}

.content-table th,
.content-table td {
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--color-border);
}

.content-table th {
  background-color: var(--color-surface-subtle);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

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

.content-table tbody tr:hover {
  background-color: var(--color-surface-subtle);
}

/* --------------------------------------------------------------------------
   8. FAQ Accordion
   -------------------------------------------------------------------------- */
.faq-accordion {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.faq-item {
  border: 1px solid var(--color-border);
  background-color: var(--color-surface);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.faq-item:hover {
  border-color: var(--color-border-hover);
}

.faq-trigger {
  width: 100%;
  padding: var(--space-4) var(--space-5);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  text-align: left;
  background: none;
}

.faq-trigger:hover {
  background-color: var(--color-surface-subtle);
}

.faq-icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  transition: transform var(--transition-base);
}

.faq-item.active .faq-icon {
  transform: rotate(180deg);
}

.faq-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-smooth), padding var(--transition-smooth);
}

.faq-item.active .faq-content {
  max-height: 400px;
}

.faq-body {
  padding: 0 var(--space-5) var(--space-5);
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.65;
}

.faq-body p:last-child {
  margin-bottom: 0;
}

/* --------------------------------------------------------------------------
   9. Site Footer
   -------------------------------------------------------------------------- */
.site-footer {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-12) 0 var(--space-6);
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-8);
  margin-bottom: var(--space-10);
}

.footer-brand p {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  max-width: 320px;
  margin-top: var(--space-3);
  margin-bottom: 0;
}

.footer-title {
  font-size: 0.95rem;
  font-weight: var(--font-weight-bold);
  color: var(--color-text-primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-4);
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.footer-link {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  transition: color var(--transition-fast);
}

.footer-link:hover {
  color: var(--color-accent);
}

.footer-bottom {
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.footer-badges {
  display: flex;
  gap: var(--space-3);
}

.badge-tag {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  background-color: var(--color-surface-subtle);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
}

/* --------------------------------------------------------------------------
   10. Forms (Contact, inputs general)
   -------------------------------------------------------------------------- */
.form-group {
  margin-bottom: var(--space-5);
}

.form-label {
  display: block;
  font-size: 0.9rem;
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  margin-bottom: var(--space-2);
}

.form-control {
  width: 100%;
  padding: 0.75rem 1rem;
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-surface);
  color: var(--color-text-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-control:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-ring);
}

textarea.form-control {
  min-height: 120px;
  resize: vertical;
}

/* --------------------------------------------------------------------------
   11. Breadcrumbs
   -------------------------------------------------------------------------- */
.breadcrumb-nav {
  padding: var(--space-4) 0;
  font-size: 0.875rem;
}

.breadcrumb-list {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  list-style: none;
  flex-wrap: wrap;
}

.breadcrumb-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--color-text-muted);
}

.breadcrumb-item a {
  color: var(--color-text-secondary);
}

.breadcrumb-item a:hover {
  color: var(--color-accent);
}

.breadcrumb-item.active {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-medium);
}

/* --------------------------------------------------------------------------
   12. Utilities & Toast Notifications
   -------------------------------------------------------------------------- */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

.toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  pointer-events: none;
}

.toast {
  pointer-events: auto;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  background-color: var(--color-text-primary);
  color: var(--color-text-inverse);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  font-size: 0.9rem;
  font-weight: var(--font-weight-medium);
  animation: toastIn 200ms cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

@keyframes toastIn {
  from {
    opacity: 0;
    transform: translateY(12px) scale(0.96);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

/* Reduced motion preference */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* --------------------------------------------------------------------------
   13. Theme & Customization Controls (Header / Drawer)
   -------------------------------------------------------------------------- */
.appearance-toggle-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background-color: var(--color-surface-subtle);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast);
}

.appearance-toggle-btn:hover {
  background-color: var(--color-surface-hover);
  color: var(--color-accent);
  transform: rotate(15deg);
}

/* Modal Overlay & Drawer for Appearance Customization */
.customizer-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-base), visibility var(--transition-base);
}

.customizer-backdrop.active {
  opacity: 1;
  visibility: visible;
}

.customizer-panel {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  width: 100%;
  max-width: 380px;
  background-color: var(--color-surface);
  border-left: 1px solid var(--color-border);
  box-shadow: var(--shadow-card);
  z-index: 1001;
  transform: translateX(100%);
  transition: transform var(--transition-smooth);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.customizer-backdrop.active .customizer-panel {
  transform: translateX(0);
}

.customizer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-6);
  border-bottom: 1px solid var(--color-border);
}

.customizer-title {
  font-size: 1.15rem;
  font-weight: var(--font-weight-bold);
  margin-bottom: 0;
}

.customizer-close-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  color: var(--color-text-muted);
  transition: background-color var(--transition-fast), color var(--transition-fast);
}

.customizer-close-btn:hover {
  background-color: var(--color-surface-subtle);
  color: var(--color-text-primary);
}

.customizer-body {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.customizer-section-title {
  font-size: 0.85rem;
  font-weight: var(--font-weight-bold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
}

.theme-options-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-2);
}

.theme-option-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-surface-subtle);
  font-size: 0.85rem;
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  transition: all var(--transition-fast);
}

.theme-option-btn.active, .theme-option-btn:hover {
  border-color: var(--color-accent);
  background-color: var(--color-surface);
  box-shadow: 0 0 0 2px var(--color-accent-ring);
}

.theme-preview-dot {
  width: 14px;
  height: 14px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(0,0,0,0.2);
}

.accent-options-grid {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.accent-btn {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  border: 2px solid transparent;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.accent-btn:hover {
  transform: scale(1.15);
}

.accent-btn.active {
  box-shadow: 0 0 0 2px var(--color-surface), 0 0 0 4px var(--color-accent);
  transform: scale(1.1);
}

.font-scale-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-2);
}

.font-scale-btn {
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-surface-subtle);
  font-weight: var(--font-weight-medium);
  font-size: 0.85rem;
  text-align: center;
  transition: all var(--transition-fast);
}

.font-scale-btn.active, .font-scale-btn:hover {
  border-color: var(--color-accent);
  background-color: var(--color-surface);
  color: var(--color-accent);
}

/* --------------------------------------------------------------------------
   14. Print Stylesheet
   -------------------------------------------------------------------------- */
@media print {
  *, *::before, *::after {
    background: transparent !important;
    color: #000 !important;
    box-shadow: none !important;
    text-shadow: none !important;
  }

  body {
    background: #fff !important;
    font-size: 12pt;
    line-height: 1.4;
  }

  .site-header,
  .mobile-nav-drawer,
  .hero-actions,
  .header-cta,
  .skip-link,
  .rounding-card,
  .tax-toggle-switch,
  .results-actions,
  .customizer-backdrop,
  .toast-container,
  .mobile-sticky-bar,
  .site-footer {
    display: none !important;
  }

  .calculator-card {
    border: 1px solid #ccc !important;
    box-shadow: none !important;
    page-break-inside: avoid;
  }

  .calculator-layout {
    display: block !important;
  }

  .calc-inputs-panel,
  .calc-results-panel {
    padding: 10px !important;
  }

  .result-highlight-card {
    border: 2px solid #000 !important;
    padding: 15px !important;
    text-align: center;
  }

  .comparison-table-wrapper {
    page-break-inside: avoid;
  }

  a[href]::after {
    content: "";
  }
}