@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Plus+Jakarta+Sans:wght@500;600;700;800&display=swap');

:root {
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-display: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;

  /* Premium Light Mode Palette */
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-result: #f1f5f9;
  --border-color: #e2e8f0;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  
  --primary-color: #4f46e5;
  --primary-hover: #3730a3;
  --primary-gradient: linear-gradient(135deg, #4f46e5 0%, #2563eb 100%);
  --accent-color: #06b6d4;
  --accent-gradient: linear-gradient(135deg, #06b6d4 0%, #3b82f6 100%);
  --contrast-color: #8b5cf6;
  --contrast-gradient: linear-gradient(135deg, #8b5cf6 0%, #d946ef 100%);
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.04), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
  --shadow-premium: 0 10px 30px -10px rgba(0, 0, 0, 0.04);
  --glow-inset: inset 0 1px 0 rgba(255, 255, 255, 0.6);
  
  --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  
  --input-focus-ring: rgba(79, 70, 229, 0.15);
}

[data-theme="dark"] {
  /* Premium Dark Mode Palette */
  --bg-page: #030712;
  --bg-card: #0b0f19;
  --bg-result: #111827;
  --border-color: #1f2937;
  --text-primary: #f9fafb;
  --text-secondary: #9ca3af;
  --text-muted: #6b7280;
  
  --primary-color: #6366f1;
  --primary-hover: #818cf8;
  --primary-gradient: linear-gradient(135deg, #6366f1 0%, #3b82f6 100%);
  --accent-color: #22d3ee;
  --accent-gradient: linear-gradient(135deg, #22d3ee 0%, #60a5fa 100%);
  --contrast-color: #a78bfa;
  --contrast-gradient: linear-gradient(135deg, #a78bfa 0%, #f472b6 100%);
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
  --shadow-premium: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
  --glow-inset: inset 0 1px 0 rgba(255, 255, 255, 0.05);
  
  --input-focus-ring: rgba(99, 102, 241, 0.25);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    /* Auto dark mode variables mapping */
    --bg-page: #030712;
    --bg-card: #0b0f19;
    --bg-result: #111827;
    --border-color: #1f2937;
    --text-primary: #f9fafb;
    --text-secondary: #9ca3af;
    --text-muted: #6b7280;
    
    --primary-color: #6366f1;
    --primary-hover: #818cf8;
    --primary-gradient: linear-gradient(135deg, #6366f1 0%, #3b82f6 100%);
    --accent-color: #22d3ee;
    --accent-gradient: linear-gradient(135deg, #22d3ee 0%, #60a5fa 100%);
    --contrast-color: #a78bfa;
    --contrast-gradient: linear-gradient(135deg, #a78bfa 0%, #f472b6 100%);
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.5);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 20px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
    --shadow-premium: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
    --glow-inset: inset 0 1px 0 rgba(255, 255, 255, 0.05);
    
    --input-focus-ring: rgba(99, 102, 241, 0.25);
  }
}

* {
  box-sizing: border-box;
}

body {
  font-family: var(--font-sans);
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-page);
  background: radial-gradient(at 0% 0%, rgba(79, 70, 229, 0.03) 0px, transparent 50%), radial-gradient(at 100% 0%, rgba(6, 182, 212, 0.03) 0px, transparent 50%), var(--bg-page);
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  transition: background-color var(--transition-normal), color var(--transition-normal), background var(--transition-normal);
  -webkit-font-smoothing: antialiased;
}
[data-theme="dark"] body {
  background: radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.08) 0px, transparent 50%), radial-gradient(at 100% 0%, rgba(34, 211, 238, 0.08) 0px, transparent 50%), var(--bg-page);
}

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

.skip-link {
  position: absolute;
  top: -60px;
  left: 10px;
  background: var(--primary-gradient);
  color: #fff;
  padding: 10px 20px;
  z-index: 1000;
  font-weight: 600;
  text-decoration: none;
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
  transition: top var(--transition-fast);
}
.skip-link:focus {
  top: 10px;
}

/* Header & Nav Layout */
.site-header {
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  background-color: rgba(255, 255, 255, 0.85);
  border-bottom: 1px solid var(--border-color);
  width: 100%;
  position: sticky;
  top: 0;
  z-index: 100;
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
  box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.02);
}
[data-theme="dark"] .site-header {
  background-color: rgba(3, 7, 18, 0.85);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .site-header {
    background-color: rgba(3, 7, 18, 0.85);
  }
  :root:not([data-theme="light"]) body {
    background: radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.08) 0px, transparent 50%), radial-gradient(at 100% 0%, rgba(34, 211, 238, 0.08) 0px, transparent 50%), #030712;
  }
}

.main-nav {
  max-width: 1050px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  width: 100%;
}

.nav-logo {
  display: flex;
  align-items: center;
  text-decoration: none;
  font-weight: 800;
  font-family: var(--font-display);
  font-size: 1.25rem;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  transition: opacity var(--transition-fast);
}
.nav-logo:hover {
  opacity: 0.9;
}
.nav-logo svg {
  transition: transform 0.3s ease;
}
.nav-logo:hover svg {
  transform: scale(1.1);
}
.logo-text {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
}

.main-nav .nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  padding: 8px 12px;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  font-size: 0.9rem;
  font-family: var(--font-display);
}
.main-nav .nav-link:hover,
.main-nav .nav-link[aria-current="page"] {
  color: var(--text-primary);
  background-color: var(--bg-result);
}
.main-nav .nav-link[aria-current="page"] {
  font-weight: 700;
  color: var(--primary-color);
}

.nav-controls {
  display: flex;
  align-items: center;
  gap: 12px;
}

.theme-toggle {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 6px 12px;
  cursor: pointer;
  color: var(--text-primary);
  font-size: 0.85rem;
  font-weight: 600;
  font-family: var(--font-display);
  transition: all var(--transition-fast);
  box-shadow: var(--shadow-sm);
}
.theme-toggle:hover {
  background: var(--bg-result);
  transform: translateY(-1px);
}
.theme-toggle:focus-visible {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

.currency-select-wrap {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  color: var(--text-secondary);
}
.currency-select-wrap select {
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 6px 10px;
  background: var(--bg-card);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.85rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}
.currency-select-wrap select:hover {
  background: var(--bg-result);
}
.currency-select-wrap select:focus-visible {
  outline: 2px solid var(--primary-color);
  border-color: var(--primary-color);
}

/* Page Containers */
.container {
  max-width: 900px;
  width: 100%;
  padding: 40px 24px;
  flex: 1;
}

h1 {
  font-family: var(--font-display);
  font-weight: 800;
  text-align: center;
  font-size: 2.3rem;
  margin: 0 0 10px;
  letter-spacing: -0.02em;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.page-subtitle {
  text-align: center;
  color: var(--text-secondary);
  margin: 0 0 36px;
  font-size: 1.05rem;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.share-bar {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 30px;
}
.share-bar button {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 8px 18px;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 0.88rem;
  font-weight: 600;
  font-family: var(--font-display);
  box-shadow: var(--shadow);
  transition: all var(--transition-fast);
}
.share-bar button:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}
.share-bar button:active {
  transform: translateY(0);
}

/* Layouts */
.calculator-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 30px;
  align-items: start;
  margin-top: 24px;
}
@media (min-width: 900px) {
  .calculator-layout {
    grid-template-columns: 4.5fr 5.5fr;
    gap: 32px;
  }
  .calculator-layout > .left-col {
    position: sticky;
    top: 80px;
  }
}

/* Forms */
.calculator-form {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 30px;
  box-shadow: var(--shadow-premium), var(--glow-inset);
}
.calculator-form .form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.form-group {
  display: flex;
  flex-direction: column;
}
.form-group.full-width {
  grid-column: 1 / -1;
}

.calculator-form label {
  margin-bottom: 8px;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.calculator-form input,
.calculator-form select {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 0.98rem;
  font-family: var(--font-sans);
  background: var(--bg-page);
  color: var(--text-primary);
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.02);
  transition: all var(--transition-fast);
}
.calculator-form input:hover,
.calculator-form select:hover {
  border-color: var(--text-muted);
}
.calculator-form input:focus,
.calculator-form select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 4px var(--input-focus-ring), inset 0 1px 2px rgba(0, 0, 0, 0.02);
}

.input-hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 6px;
}

/* Results section */
.results {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  background: var(--bg-card);
  padding: 30px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow-premium), var(--glow-inset);
  position: relative;
  overflow: hidden;
}
.results::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: var(--primary-gradient);
}
.results.single {
  grid-template-columns: 1fr;
}
.results[hidden] {
  display: none;
}

.result-item {
  text-align: center;
  padding: 10px;
}
.result-item .label {
  color: var(--text-muted);
  font-family: var(--font-display);
  font-size: 0.75rem;
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 700;
}
.result-item .value {
  font-size: 1.9rem;
  font-weight: 800;
  font-family: var(--font-display);
  letter-spacing: -0.02em;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-variant-numeric: tabular-nums;
  display: inline-block;
  animation: numFadeIn 0.3s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

@keyframes numFadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

.right-col {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Chart */
.chart-wrap {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-premium), var(--glow-inset);
}
.chart-wrap[hidden] {
  display: none;
}
.chart-wrap svg {
  width: 100%;
  height: auto;
  display: block;
}
.chart-wrap .legend {
  display: flex;
  gap: 20px;
  justify-content: center;
  margin-top: 18px;
  font-size: 0.85rem;
  font-family: var(--font-display);
  font-weight: 500;
  color: var(--text-secondary);
}
.chart-wrap .legend span::before {
  content: "";
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 3px;
  margin-right: 8px;
  vertical-align: middle;
}
.chart-wrap .legend .bal::before {
  background: var(--primary-color);
}
.chart-wrap .legend .con::before {
  background: var(--contrast-color);
}

/* Amortization Schedule Table */
.schedule-toggle {
  margin-top: 30px;
  width: 100%;
  padding: 12px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-family: var(--font-display);
  cursor: pointer;
  text-align: left;
  color: var(--text-primary);
  box-shadow: var(--shadow);
  transition: all var(--transition-fast);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.schedule-toggle:hover {
  background: var(--bg-result);
  border-color: var(--primary-color);
}
.schedule-toggle:focus-visible {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}
.schedule-toggle[hidden] {
  display: none;
}

#schedule-container {
  margin-top: 20px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.schedule-table {
  width: 100%;
  border-collapse: collapse;
  font-variant-numeric: tabular-nums;
  font-size: 0.9rem;
}
.schedule-table th,
.schedule-table td {
  padding: 12px 18px;
  text-align: right;
  border-bottom: 1px solid var(--border-color);
}
.schedule-table th:first-child,
.schedule-table td:first-child {
  text-align: left;
}
.schedule-table th {
  background-color: var(--bg-result);
  position: sticky;
  top: 0;
  font-family: var(--font-display);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 700;
  color: var(--text-muted);
}
.schedule-table tr:last-child td {
  border-bottom: none;
}
.schedule-table tr:hover td {
  background-color: rgba(79, 70, 229, 0.02);
}
[data-theme="dark"] .schedule-table tr:hover td {
  background-color: rgba(99, 102, 241, 0.04);
}
.schedule-table tr.highlight td {
  background: rgba(79, 70, 229, 0.08);
  font-weight: 600;
}
[data-theme="dark"] .schedule-table tr.highlight td {
  background: rgba(99, 102, 241, 0.12);
}

/* Formulas Section */
.formulas {
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
  font-size: 0.88rem;
  color: var(--text-secondary);
}
.formulas h3 {
  font-family: var(--font-display);
  color: var(--text-primary);
  margin-top: 0;
}
.formulas ul {
  padding-left: 20px;
  margin: 8px 0;
}
.formulas code {
  background: var(--bg-result);
  color: var(--primary-color);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.85em;
  font-family: SFMono-Regular, Consolas, "Liberation Mono", Menlo, monospace;
}

/* Cashflow Rows (NPV) */
.cashflow-list {
  margin-top: 12px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.cashflow-row {
  display: grid;
  grid-template-columns: 100px 1fr auto;
  gap: 12px;
  align-items: center;
}
.cashflow-row input {
  padding: 10px 12px;
}
.cashflow-row .del-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  width: 38px;
  height: 38px;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 1.2rem;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}
.cashflow-row .del-btn:hover {
  color: #ef4444;
  border-color: #fca5a5;
  background: #fef2f2;
}
[data-theme="dark"] .cashflow-row .del-btn:hover {
  background: #7f1d1d;
  border-color: #ef4444;
  color: #fca5a5;
}

.add-row-btn {
  background: var(--bg-card);
  border: 1px dashed var(--primary-color);
  color: var(--primary-color);
  padding: 10px 18px;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-weight: 600;
  font-family: var(--font-display);
  font-size: 0.88rem;
  margin-top: 12px;
  transition: all var(--transition-fast);
  align-self: flex-start;
}
.add-row-btn:hover {
  background: var(--bg-result);
  border-style: solid;
}

/* Landing Page (Hero + Calc cards) */
.hero {
  text-align: center;
  margin-bottom: 48px;
  padding: 40px 12px 10px;
}
.hero h1 {
  font-size: 3rem;
  margin-bottom: 16px;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero .lede {
  color: var(--text-secondary);
  font-size: 1.15rem;
  max-width: 680px;
  margin: 0 auto 30px;
  line-height: 1.6;
}
.hero .cta-row {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}
.hero .cta {
  display: inline-block;
  padding: 12px 24px;
  background: var(--primary-gradient);
  color: #fff;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-family: var(--font-display);
  font-size: 0.95rem;
  box-shadow: var(--shadow-md);
  transition: all var(--transition-fast);
}
.hero .cta:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  opacity: 0.95;
}
.hero .cta.secondary {
  background: var(--bg-card);
  color: var(--primary-color);
  border: 1px solid var(--border-color);
}
.hero .cta.secondary:hover {
  border-color: var(--primary-color);
  color: var(--primary-hover);
}

.section-heading {
  font-family: var(--font-display);
  font-size: 1.6rem;
  font-weight: 700;
  margin: 48px 0 20px;
  text-align: center;
  letter-spacing: -0.01em;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin: 0 0 48px;
}

.calc-card {
  display: block;
  padding: 24px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  color: var(--text-primary);
  box-shadow: var(--shadow);
  transition: all var(--transition-normal);
  position: relative;
}
.calc-card::after {
  content: "";
  position: absolute;
  top: 0; left: 0; width: 100%; height: 100%;
  border-radius: var(--radius-lg);
  box-shadow: 0 0 30px rgba(79, 70, 229, 0.05);
  opacity: 0;
  transition: opacity var(--transition-fast);
  pointer-events: none;
}
.calc-card:hover {
  transform: translateY(-4px);
  border-color: var(--primary-color);
  box-shadow: var(--shadow-lg);
  color: var(--text-primary);
}
.calc-card:hover::after {
  opacity: 1;
}

.calc-card .icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  background: var(--bg-result);
  color: var(--primary-color);
  border-radius: var(--radius-md);
  font-weight: 800;
  font-size: 1.3rem;
  margin-bottom: 16px;
  transition: all var(--transition-fast);
}
.calc-card:hover .icon {
  background: var(--primary-gradient);
  color: #fff;
}

.calc-card h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 700;
  margin: 0 0 8px;
  color: var(--text-primary);
}
.calc-card p {
  font-size: 0.88rem;
  color: var(--text-secondary);
  margin: 0;
  line-height: 1.5;
}

/* Principles Grid */
.principles {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
  margin: 24px 0 48px;
}
.principle {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  box-shadow: var(--shadow);
  transition: border-color var(--transition-fast);
}
.principle:hover {
  border-color: var(--primary-color);
}
.principle strong {
  display: block;
  font-family: var(--font-display);
  color: var(--text-primary);
  margin-bottom: 6px;
  font-size: 0.98rem;
}
.principle span {
  color: var(--text-secondary);
  font-size: 0.85rem;
  line-height: 1.45;
}

/* Content & FAQs */
.content-section {
  max-width: 720px;
  margin: 48px auto 0;
}
.content-section h2 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  margin: 0 0 16px;
  color: var(--text-primary);
}
.content-section h3 {
  font-family: var(--font-display);
  font-size: 1.12rem;
  margin: 20px 0 8px;
  color: var(--text-primary);
}
.content-section p,
.content-section li {
  color: var(--text-secondary);
  line-height: 1.6;
  margin: 0 0 12px;
}
.content-section ul {
  padding-left: 20px;
}

details.faq,
details.example,
details.howit {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 14px 18px;
  margin: 10px 0;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}
details.faq[open],
details.example[open],
details.howit[open] {
  background: var(--bg-card);
  box-shadow: var(--shadow);
  border-color: var(--primary-color);
}
details > summary {
  cursor: pointer;
  font-family: var(--font-display);
  font-weight: 600;
  color: var(--text-primary);
  list-style: none;
  padding: 4px 0;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.95rem;
}
details > summary::-webkit-details-marker {
  display: none;
}
details > summary::before {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  border-right: 2px solid var(--primary-color);
  border-bottom: 2px solid var(--primary-color);
  transform: rotate(-45deg);
  transition: transform var(--transition-fast) ease;
  margin-left: 4px;
  margin-right: 12px;
  flex-shrink: 0;
}
details[open] > summary::before {
  transform: rotate(45deg);
}

details > .answer,
details > .body {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.92rem;
}
details > .answer code,
details > .body code {
  background: var(--bg-result);
  color: var(--primary-color);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.88em;
}

/* Footer styling */
.site-footer {
  margin-top: 80px;
  padding: 30px 20px;
  border-top: 1px solid var(--border-color);
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
  width: 100%;
  background-color: var(--bg-card);
}
.site-footer nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px 24px;
  margin-bottom: 12px;
}
.site-footer a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  font-weight: 500;
}
.site-footer a:hover {
  color: var(--primary-color);
}

.prose {
  max-width: 720px;
  margin: 0 auto;
}
.prose h2 {
  font-family: var(--font-display);
  margin-top: 36px;
  color: var(--text-primary);
}
.prose p,
.prose li {
  color: var(--text-secondary);
}

.error-msg {
  color: #ef4444;
  font-size: 0.82rem;
  margin-top: 6px;
  font-weight: 500;
}

/* Mobile responsive fixes */
@media (max-width: 640px) {
  .calculator-form .form-grid,
  .results {
    grid-template-columns: 1fr;
  }
  .main-nav {
    flex-direction: column;
    gap: 10px;
    padding: 12px 10px;
    align-items: center;
  }
  .nav-logo {
    font-size: 1.15rem;
  }
  .nav-links {
    flex-wrap: wrap;
    justify-content: center;
    gap: 4px;
  }
  .main-nav .nav-link {
    font-size: 0.82rem;
    padding: 4px 8px;
  }
  .nav-controls {
    justify-content: center;
    width: 100%;
    gap: 8px;
  }
  .theme-toggle,
  .currency-select-wrap select {
    font-size: 0.78rem;
    padding: 4px 8px;
  }
  .container {
    padding: 20px 16px;
  }
  h1 {
    font-size: 1.8rem;
  }
  .hero h1 {
    font-size: 2.2rem;
  }
  .hero .lede {
    font-size: 0.98rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
    animation: none !important;
  }
}