/* ============================================
   FINANCE MINIMAL - ABOUT PAGE
   ============================================ */

:root {
  /* Finance Minimal Color Palette */
  --fin-bg: #F8FAFC;
  --fin-card: #FFFFFF;
  --fin-primary: #1E40AF;
  --fin-primary-light: #3B82F6;
  --fin-secondary: #64748B;
  --fin-accent-green: #059669;
  --fin-accent-green-light: #10B981;
  --fin-accent-red: #DC2626;
  --fin-accent-amber: #D97706;
  --fin-text: #1E293B;
  --fin-text-muted: #64748B;
  --fin-text-light: #94A3B8;
  --fin-border: #E2E8F0;
  --fin-border-focus: #3B82F6;
  --fin-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --fin-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
  --fin-shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.04);
  --fin-radius: 12px;
  --fin-radius-sm: 8px;
  --fin-radius-xs: 6px;
  --fin-transition: 0.2s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", Roboto, "Helvetica Neue", Arial,
    sans-serif;
  background-color: var(--fin-bg);
  color: var(--fin-text);
  line-height: 1.65;
  min-height: 100vh;
  padding: 32px 20px 80px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ---------- Container ---------- */
.page-container {
  max-width: 800px;
  margin: 0 auto;
}

/* ---------- Header ---------- */
.page-header {
  text-align: center;
  margin-bottom: 40px;
  position: relative;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--fin-secondary);
  text-decoration: none;
  margin-bottom: 20px;
  padding: 10px 20px;
  background: var(--fin-card);
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius-sm);
  box-shadow: var(--fin-shadow-sm);
  transition: var(--fin-transition);
}

.back-link:hover {
  color: var(--fin-primary);
  border-color: var(--fin-primary);
}

.back-link:active {
  transform: translate(0, 0);
}

.back-link svg {
  transition: transform var(--fin-transition);
}

.back-link:hover svg {
  transform: translateX(-4px);
}

.page-header h1 {
  font-size: clamp(1.4rem, 5vw, 1.8rem);
  font-weight: 700;
  color: var(--fin-text);
  letter-spacing: -0.5px;
  position: relative;
  display: inline-block;
  padding-bottom: 12px;
}

.page-header h1::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 50px;
  height: 3px;
  background: var(--fin-primary);
  border-radius: 2px;
}

.page-header .subtitle {
  font-size: 0.9rem;
  color: var(--fin-text-muted);
  margin-top: 16px;
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.5;
}

/* ---------- Cards ---------- */
.card {
  background: var(--fin-card);
  padding: 32px 28px;
  box-shadow: var(--fin-shadow);
  margin-bottom: 24px;
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius);
  transition: box-shadow var(--fin-transition);
}

.card:hover {
  box-shadow: var(--fin-shadow-lg);
}

/* Card Titles */
.card h2 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--fin-text);
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.card h2::before {
  content: "";
  width: 6px;
  height: 6px;
  background: var(--fin-primary);
  border-radius: 50%;
  flex-shrink: 0;
}

.card h3 {
  font-size: 0.9rem;
  font-weight: 600;
  margin: 20px 0 10px;
  color: var(--fin-text);
  padding-left: 12px;
  border-left: 3px solid var(--fin-primary-light);
}

/* Card Content */
.card p {
  font-size: 0.9rem;
  color: var(--fin-text);
  margin-bottom: 12px;
  line-height: 1.7;
}

.card ul {
  margin: 12px 0 12px 20px;
}

.card ul li {
  margin-bottom: 8px;
  padding-left: 6px;
  line-height: 1.6;
  color: var(--fin-text-muted);
}

/* ---------- Formula Box (Finance Minimal Style) ---------- */
.formula-box {
  background: var(--fin-card);
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius-sm);
  padding: 0;
  margin: 16px 0;
  box-shadow: var(--fin-shadow-sm);
  overflow: hidden;
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
}

.formula-box .formula-main {
  background: var(--fin-primary);
  color: #fff;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 14px 20px;
  text-align: center;
  letter-spacing: 0.3px;
}

.formula-box .formula-legend {
  padding: 16px 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.formula-box .legend-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 10px 14px;
  background: var(--fin-bg);
  border-radius: var(--fin-radius-xs);
}

.formula-box .legend-var {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 32px;
  height: 28px;
  background: var(--fin-primary);
  color: #fff;
  font-weight: 600;
  font-size: 0.8rem;
  border-radius: var(--fin-radius-xs);
  flex-shrink: 0;
}

/* Old Method Formula - Card Style */
.formula-box .formula-old {
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.formula-box .formula-row {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  background: var(--fin-bg);
  border-radius: var(--fin-radius-xs);
  gap: 12px;
}

.formula-box .formula-label {
  font-weight: 600;
  min-width: 150px;
  color: var(--fin-primary);
  flex-shrink: 0;
  font-size: 0.85rem;
}

.formula-box .formula-eq {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--fin-text);
  flex-shrink: 0;
}

.formula-box .formula-expr {
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  color: var(--fin-text-muted);
  flex: 1;
}

/* Monthly Calculation Formulas */
.calc-formulas {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin: 12px 0;
}

.calc-formula-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  background: var(--fin-bg);
  border-radius: var(--fin-radius-sm);
  transition: var(--fin-transition);
}

.calc-formula-item:hover {
  background: var(--fin-card);
  box-shadow: var(--fin-shadow-sm);
}

.calc-formula-item .calc-label {
  font-weight: 600;
  color: var(--fin-secondary);
  min-width: 160px;
}

.calc-formula-item .calc-eq {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--fin-primary);
}

.calc-formula-item .calc-expr {
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  color: var(--fin-text-muted);
  flex: 1;
}

@media (max-width: 480px) {
  .formula-box .formula-row {
    flex-wrap: wrap;
    gap: 8px;
    padding: 12px 16px;
  }

  .formula-box .formula-label {
    min-width: 100%;
    padding-bottom: 4px;
    border-bottom: 1px dashed var(--fin-border);
  }

  .calc-formula-item {
    flex-wrap: wrap;
    gap: 8px;
  }

  .calc-formula-item .calc-label {
    min-width: 100%;
  }
}

/* ---------- Calculation Steps ---------- */
.calc-step {
  background: var(--fin-bg);
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius-sm);
  padding: 18px 22px;
  margin: 16px 0;
  font-size: 0.9rem;
  color: var(--fin-text);
  transition: var(--fin-transition);
}

.calc-step:hover {
  box-shadow: var(--fin-shadow-sm);
}

.calc-step .step-title {
  font-weight: 600;
  color: var(--fin-primary);
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.step-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  background: var(--fin-primary);
  color: #fff;
  border-radius: 50%;
  font-weight: 600;
  font-size: 0.8rem;
}

.rate-change-up {
  color: var(--fin-accent-red);
  font-weight: 600;
}

.rate-change-down {
  color: var(--fin-accent-green);
  font-weight: 600;
}

.savings {
  color: var(--fin-accent-green);
  font-weight: 600;
}

/* ---------- Expandable Sections ---------- */
details {
  margin-bottom: 16px;
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius-sm);
  overflow: hidden;
  box-shadow: var(--fin-shadow-sm);
  transition: box-shadow var(--fin-transition);
}

details:hover {
  box-shadow: var(--fin-shadow);
}

details[open] {
  box-shadow: var(--fin-shadow);
}

details summary {
  padding: 14px 20px;
  background: var(--fin-primary);
  font-weight: 600;
  font-size: 0.85rem;
  color: #fff;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background var(--fin-transition);
}

details summary:hover {
  background: var(--fin-primary-light);
}

details summary::-webkit-details-marker {
  display: none;
}

details summary::after {
  content: "+";
  font-size: 1.4rem;
  font-weight: 500;
  margin-left: 12px;
}

details[open] summary::after {
  content: "−";
}

.details-content {
  padding: 20px;
  background: var(--fin-card);
  animation: slideDown 0.3s ease;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ---------- Note Box ---------- */
.note {
  font-size: 0.85rem !important;
  color: var(--fin-text-muted) !important;
  padding: 14px 18px !important;
  background: var(--fin-bg) !important;
  border-left: 3px solid var(--fin-accent-amber) !important;
  margin: 16px 0 !important;
  border-radius: 0 var(--fin-radius-xs) var(--fin-radius-xs) 0;
}

/* ---------- Tables ---------- */
.table-wrap {
  max-height: 500px;
  overflow-y: auto;
  overflow-x: auto;
  border-radius: var(--fin-radius-sm);
  border: 1px solid var(--fin-border);
  box-shadow: var(--fin-shadow-sm);
  margin: 16px 0;
  -webkit-overflow-scrolling: touch;
}

.table-wrap::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

.table-wrap::-webkit-scrollbar-track {
  background: var(--fin-bg);
}

.table-wrap::-webkit-scrollbar-thumb {
  background: var(--fin-text-light);
  border-radius: 4px;
}

.table-wrap::-webkit-scrollbar-thumb:hover {
  background: var(--fin-secondary);
}

.example-table,
.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
  min-width: 480px;
}

.example-table th,
.example-table td,
.comparison-table th,
.comparison-table td {
  border: 1px solid var(--fin-border);
  padding: 10px 12px;
  text-align: right;
}

.example-table th,
.comparison-table th {
  background: var(--fin-primary);
  color: #fff;
  font-weight: 600;
  text-align: center;
  font-size: 0.7rem;
  white-space: nowrap;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

.example-table td:first-child,
.comparison-table td:first-child {
  text-align: center;
  font-weight: 600;
  color: var(--fin-text);
  background: var(--fin-bg);
}

.example-table tbody tr,
.comparison-table tbody tr {
  transition: background var(--fin-transition);
}

.example-table tbody tr:hover td:not(:first-child),
.comparison-table tbody tr:hover td:not(:first-child) {
  background: var(--fin-bg);
}

.highlight-row {
  background: rgba(30, 64, 175, 0.05) !important;
}

.total-row {
  font-weight: 600;
  background: var(--fin-bg) !important;
}

/* ---------- Disclaimer Box ---------- */
.disclaimer-box {
  background: var(--fin-bg);
  border: 1px solid var(--fin-border);
  border-radius: var(--fin-radius-sm);
  padding: 20px 24px;
  margin: 24px 0;
  font-size: 0.85rem;
  color: var(--fin-text-muted);
  line-height: 1.6;
}

.disclaimer-box strong {
  color: var(--fin-text);
}

body {
    user-select: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
}

input, textarea, select {
    user-select: text;
    -webkit-user-select: text;
    -moz-user-select: text;
    -ms-user-select: text;
}

/* ---------- Official Link Button ---------- */
.official-link {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-top: 16px;
  padding: 12px 24px;
  background: var(--fin-primary);
  color: #fff;
  border-radius: var(--fin-radius-sm);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 600;
  transition: var(--fin-transition);
}

.official-link:hover {
  background: var(--fin-primary-light);
  box-shadow: var(--fin-shadow);
}

.official-link:active {
  transform: translate(0, 0);
}

/* ---------- Floating Back Button ---------- */
.floating-back-btn {
  position: fixed;
  bottom: 32px;
  left: 32px;
  width: 52px;
  height: 52px;
  background: var(--fin-primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  box-shadow: var(--fin-shadow-lg);
  z-index: 1000;
  transition: var(--fin-transition);
}

.floating-back-btn:hover {
  background: var(--fin-primary-light);
  box-shadow: 0 10px 25px rgba(30, 64, 175, 0.3);
}

.floating-back-btn:active {
  transform: scale(0.95);
}

/* ---------- Footer ---------- */
footer {
  text-align: center;
  padding: 24px 0;
  margin-top: 32px;
  font-size: 0.85rem;
  color: var(--fin-text-light);
  border-top: 1px solid var(--fin-border);
}

footer a {
  color: var(--fin-primary);
  text-decoration: none;
  font-weight: 500;
  transition: color var(--fin-transition);
}

footer a:hover {
  color: var(--fin-primary-light);
}

/* ---------- Responsive ---------- */
@media (max-width: 768px) {
  body {
    padding: 20px 16px 70px;
  }

  .card {
    padding: 24px 20px;
  }

  .page-header {
    margin-bottom: 28px;
  }

  .page-header h1 {
    font-size: 1.3rem;
  }

  .back-link {
    font-size: 0.75rem;
    padding: 8px 16px;
  }

  .example-table,
  .comparison-table {
    font-size: 0.8rem;
    min-width: 400px;
  }

  .table-wrap {
    max-height: 350px;
  }
}

@media (max-width: 480px) {
  body {
    padding: 16px 12px 80px;
  }

  .card {
    padding: 20px 16px;
    margin-bottom: 20px;
  }

  .card h2 {
    font-size: 0.95rem;
  }

  .page-header h1 {
    font-size: 1.2rem;
  }

  .floating-back-btn {
    bottom: 20px;
    left: 20px;
    width: 48px;
    height: 48px;
  }

  .example-table,
  .comparison-table {
    font-size: 0.75rem;
    min-width: 360px;
  }

  .example-table th,
  .comparison-table th {
    font-size: 0.65rem;
    padding: 8px 6px;
  }

  .example-table td,
  .comparison-table td {
    padding: 8px 6px;
  }

  details summary {
    font-size: 0.8rem;
    padding: 12px 16px;
  }

  .details-content {
    padding: 16px;
  }
}

/* ---------- Print Styles ---------- */
@media print {
  .floating-back-btn,
  .back-link {
    display: none;
  }

  .card {
    box-shadow: none;
    border: 1px solid #ddd;
    break-inside: avoid;
    page-break-inside: avoid;
  }

  details {
    box-shadow: none;
  }

  .table-wrap {
    max-height: none;
    overflow: visible;
    border: 1px solid #ddd;
  }
}