:root {
  --bg: #F7F5F2;
  --card: #FFFFFF;
  --text: #1E293B;
  --muted: #64748B;
  --accent: #0F2A43;
  --teal: #2A9D8F;
  --border: #E2E0DC;
  --shadow-sm: 0 1px 2px rgba(15, 42, 67, 0.04), 0 1px 3px rgba(15, 42, 67, 0.06);
  --shadow-md: 0 4px 12px rgba(15, 42, 67, 0.08);
  --radius: 10px;
  --radius-sm: 6px;
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-display: 'Inter', system-ui, -apple-system, sans-serif;
  --spacing-1: 0.25rem;
  --spacing-2: 0.5rem;
  --spacing-3: 0.75rem;
  --spacing-4: 1rem;
  --spacing-5: 1.5rem;
  --spacing-6: 2rem;
  --spacing-7: 3rem;
  --spacing-8: 4rem;
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-body);
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.5;
  font-size: 1rem;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Header */
.site-header {
  background-color: var(--card);
  border-bottom: 1px solid var(--border);
  padding: var(--spacing-4) var(--spacing-6);
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: var(--shadow-sm);
}

.site-header .header-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-4);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-2);
  text-decoration: none;
  color: var(--accent);
  font-weight: 600;
  font-size: 1.1rem;
  letter-spacing: -0.01em;
}

.brand svg {
  flex-shrink: 0;
}

.brand:hover {
  color: var(--teal);
  transition: color 150ms ease;
}

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: var(--spacing-2) var(--spacing-3);
  cursor: pointer;
  color: var(--text);
  font-size: 1.25rem;
  line-height: 1;
}

.nav-toggle:hover {
  background-color: var(--bg);
}

.site-nav {
  display: flex;
  align-items: center;
  gap: var(--spacing-4);
}

.site-nav a {
  text-decoration: none;
  color: var(--muted);
  font-weight: 500;
  font-size: 0.95rem;
  padding: var(--spacing-1) 0;
  border-bottom: 2px solid transparent;
  transition: color 150ms ease, border-color 150ms ease;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--accent);
  border-bottom-color: var(--teal);
  outline: none;
}

/* Main layout */
.main-content {
  flex: 1;
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-6) var(--spacing-6) var(--spacing-8);
  width: 100%;
}

.calculator-grid {
  display: grid;
  grid-template-columns: 340px 1fr;
  gap: var(--spacing-6);
  align-items: start;
}

/* Input panel */
.input-panel {
  background-color: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--spacing-5);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: calc(64px + var(--spacing-4));
}

.input-panel h2 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: var(--spacing-4);
  letter-spacing: -0.01em;
}

.field-group {
  margin-bottom: var(--spacing-4);
}

.field-group label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: var(--spacing-1);
}

.input-with-suffix {
  position: relative;
  display: flex;
  align-items: center;
}

.input-with-suffix .prefix,
.input-with-suffix .suffix {
  position: absolute;
  font-size: 0.9rem;
  color: var(--muted);
  pointer-events: none;
}

.input-with-suffix .prefix {
  left: var(--spacing-3);
}

.input-with-suffix .suffix {
  right: var(--spacing-3);
}

.input-with-suffix input {
  width: 100%;
  padding: var(--spacing-2) var(--spacing-3);
  font-size: 0.95rem;
  font-family: var(--font-body);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background-color: var(--card);
  color: var(--text);
  transition: border-color 150ms ease, box-shadow 150ms ease;
  appearance: textfield;
  -moz-appearance: textfield;
}

.input-with-suffix input::-webkit-outer-spin-button,
.input-with-suffix input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.input-with-suffix input:focus {
  outline: none;
  border-color: var(--teal);
  box-shadow: 0 0 0 3px rgba(42, 157, 143, 0.15);
}

.input-with-suffix input.has-prefix {
  padding-left: calc(var(--spacing-3) + 1.25rem);
}

.input-with-suffix input.has-suffix {
  padding-right: calc(var(--spacing-3) + 1.5rem);
}

.toggle-group {
  display: flex;
  gap: var(--spacing-1);
  margin-bottom: var(--spacing-2);
  background-color: var(--bg);
  border-radius: var(--radius-sm);
  padding: 3px;
  border: 1px solid var(--border);
}

.toggle-group button {
  flex: 1;
  padding: var(--spacing-1) var(--spacing-2);
  font-size: 0.8rem;
  font-weight: 500;
  border: none;
  background: none;
  border-radius: 4px;
  cursor: pointer;
  color: var(--muted);
  transition: background-color 150ms ease, color 150ms ease;
  font-family: var(--font-body);
}

.toggle-group button.active {
  background-color: var(--card);
  color: var(--accent);
  box-shadow: var(--shadow-sm);
}

.toggle-group button:hover {
  color: var(--accent);
}

/* Results panel */
.results-panel {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-5);
}

/* Monthly payment hero */
.payment-hero {
  background-color: var(--accent);
  border-radius: var(--radius);
  padding: var(--spacing-6) var(--spacing-6);
  color: #FFFFFF;
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-1);
}

.payment-hero .payment-label {
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: rgba(255, 255, 255, 0.7);
  font-weight: 500;
}

.payment-hero .payment-amount {
  font-size: clamp(2.5rem, 5vw, 3.5rem);
  font-weight: 650;
  letter-spacing: -0.02em;
  line-height: 1.1;
  color: #FFFFFF;
}

.payment-hero .payment-note {
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.6);
}

.payment-hero .total-interest-row {
  display: flex;
  align-items: baseline;
  gap: var(--spacing-2);
  margin-top: var(--spacing-3);
  padding-top: var(--spacing-3);
  border-top: 1px solid rgba(255, 255, 255, 0.15);
}

.payment-hero .total-interest-row .interest-label {
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.7);
}

.payment-hero .total-interest-row .interest-value {
  font-size: 1.5rem;
  font-weight: 600;
  color: #FFFFFF;
}

/* Card */
.card {
  background-color: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--spacing-5);
  box-shadow: var(--shadow-sm);
}

.card h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: var(--spacing-4);
  letter-spacing: -0.01em;
}

/* Chart container */
.chart-container {
  width: 100%;
  height: 320px;
  position: relative;
}

.chart-container svg {
  width: 100%;
  height: 100%;
  display: block;
}

/* Table */
.table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.amortization-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
  min-width: 600px;
}

.amortization-table th {
  text-align: right;
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
  padding: var(--spacing-2) var(--spacing-3);
  border-bottom: 2px solid var(--border);
}

.amortization-table th:first-child {
  text-align: left;
}

.amortization-table td {
  text-align: right;
  padding: var(--spacing-2) var(--spacing-3);
  border-bottom: 1px solid var(--border);
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

.amortization-table td:first-child {
  text-align: left;
  font-weight: 500;
  color: var(--muted);
}

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

.amortization-table tbody tr:hover td {
  background-color: var(--bg);
}

.amortization-table .total-row td {
  font-weight: 600;
  color: var(--accent);
  border-top: 2px solid var(--border);
  border-bottom: none;
  background-color: var(--bg);
}

/* Footer */
.site-footer {
  background-color: var(--card);
  border-top: 1px solid var(--border);
  padding: var(--spacing-5) var(--spacing-6);
  color: var(--muted);
  font-size: 0.85rem;
}

.site-footer .footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--spacing-3);
}

.site-footer a {
  color: var(--muted);
  text-decoration: none;
}

.site-footer a:hover {
  color: var(--accent);
  text-decoration: underline;
}

/* Reveal on scroll */
html.js .reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 400ms ease, transform 400ms ease;
}

html.js .reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  html.js .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* Responsive */
@media (max-width: 900px) {
  .calculator-grid {
    grid-template-columns: 1fr;
  }
  .input-panel {
    position: static;
  }
  .site-header {
    padding: var(--spacing-3) var(--spacing-4);
  }
  .main-content {
    padding: var(--spacing-4) var(--spacing-4) var(--spacing-6);
  }
}

@media (max-width: 600px) {
  .nav-toggle {
    display: block;
  }
  .site-nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--card);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: stretch;
    padding: var(--spacing-3) var(--spacing-4);
    gap: var(--spacing-2);
    box-shadow: var(--shadow-md);
  }
  .site-nav.open {
    display: flex;
  }
  .site-nav a {
    padding: var(--spacing-2) 0;
    border-bottom: 1px solid var(--border);
  }
  .site-nav a:last-child {
    border-bottom: none;
  }
  .payment-hero {
    padding: var(--spacing-4);
  }
  .card {
    padding: var(--spacing-4);
  }
  .chart-container {
    height: 240px;
  }
}