:root {
  color-scheme: light dark;
  --bg: #0d1117;
  --surface: #161b22;
  --surface-soft: #11161d;
  --surface-raised: #21262d;
  --border: #30363d;
  --border-strong: #484f58;
  --text: #e6edf3;
  --muted: #8b949e;
  --accent: #58a6ff;
  --accent-strong: #1f6feb;
  --accent-soft: rgba(88, 166, 255, 0.12);
  --success: #3fb950;
  --warning: #d29922;
  --danger: #f85149;
  --principal: #58a6ff;
  --interest: #d29922;
  --shadow: 0 18px 45px rgba(0, 0, 0, 0.22);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --max-width: 1240px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans TC", Helvetica, Arial, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f6f8fa;
    --surface: #ffffff;
    --surface-soft: #f6f8fa;
    --surface-raised: #eaeef2;
    --border: #d0d7de;
    --border-strong: #afb8c1;
    --text: #24292f;
    --muted: #57606a;
    --accent: #0969da;
    --accent-strong: #0550ae;
    --accent-soft: rgba(9, 105, 218, 0.09);
    --success: #1a7f37;
    --warning: #9a6700;
    --danger: #cf222e;
    --principal: #0969da;
    --interest: #bf8700;
    --shadow: 0 18px 45px rgba(31, 35, 40, 0.1);
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 8% 0%, var(--accent-soft), transparent 27rem),
    var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

button,
input,
select {
  font: inherit;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

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

.skip-link {
  position: fixed;
  left: 1rem;
  top: -5rem;
  z-index: 100;
  padding: 0.7rem 1rem;
  border-radius: var(--radius-sm);
  background: var(--accent);
  color: #fff;
  text-decoration: none;
}

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

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(14px);
}

.topbar-inner {
  width: min(100% - 2rem, var(--max-width));
  min-height: 58px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  color: var(--text);
  font-size: 0.92rem;
  font-weight: 700;
  text-decoration: none;
}

.brand-mark {
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  border: 1px solid var(--border);
  border-radius: 9px;
  background: var(--surface);
  color: var(--accent);
}

.back-link {
  color: var(--muted);
  font-size: 0.88rem;
  text-decoration: none;
}

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

.container {
  width: min(100% - 2rem, var(--max-width));
  margin: 0 auto;
}

.hero {
  padding: 3.5rem 0 2rem;
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) minmax(280px, 0.7fr);
  gap: 2.5rem;
  align-items: end;
}

.eyebrow {
  margin-bottom: 0.6rem;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 760px;
  margin-bottom: 0.9rem;
  font-size: clamp(2.15rem, 6vw, 4.2rem);
  line-height: 1.03;
  letter-spacing: -0.055em;
}

.hero-copy {
  max-width: 720px;
  margin-bottom: 0;
  color: var(--muted);
  font-size: 1.02rem;
}

.hero-note {
  padding: 1.1rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  color: var(--muted);
  font-size: 0.85rem;
}

.hero-note strong {
  display: block;
  margin-bottom: 0.3rem;
  color: var(--text);
}

.action-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin-top: 1.4rem;
}

.btn {
  min-height: 42px;
  padding: 0.62rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
  transition: 150ms ease;
}

.btn:hover {
  border-color: var(--accent);
  background: var(--surface-raised);
  transform: translateY(-1px);
}

.btn-primary {
  border-color: var(--accent-strong);
  background: var(--accent-strong);
  color: #fff;
}

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

.btn:focus-visible,
input:focus-visible,
select:focus-visible,
.tab:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.form-error {
  margin-bottom: 1rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--danger);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--danger) 10%, var(--surface));
  color: var(--danger);
  font-size: 0.88rem;
}

.form-error[hidden] {
  display: none;
}

.calculator-layout {
  display: grid;
  grid-template-columns: minmax(300px, 390px) minmax(0, 1fr);
  gap: 1.25rem;
  align-items: start;
  padding-bottom: 3.5rem;
}

.panel {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--surface);
  box-shadow: var(--shadow);
}

.form-panel {
  position: sticky;
  top: 78px;
  padding: 1.25rem;
}

.fieldset {
  margin: 0;
  padding: 0;
  border: 0;
}

.fieldset + .fieldset {
  margin-top: 1.15rem;
  padding-top: 1.15rem;
  border-top: 1px solid var(--border);
}

.legend {
  margin-bottom: 0.85rem;
  padding: 0;
  color: var(--text);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.04em;
}

.field-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.85rem;
}

.field {
  min-width: 0;
}

.field-wide {
  grid-column: 1 / -1;
}

.field label,
.field-label {
  display: block;
  margin-bottom: 0.35rem;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
}

.input-wrap {
  position: relative;
}

.input-wrap input,
.field select {
  width: 100%;
  min-height: 44px;
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-soft);
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

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

.input-suffix {
  position: absolute;
  right: 0.7rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
  font-size: 0.78rem;
  pointer-events: none;
}

.input-wrap.has-suffix input {
  padding-right: 2.8rem;
}

.field-hint {
  margin: 0.35rem 0 0;
  color: var(--muted);
  font-size: 0.72rem;
  line-height: 1.5;
}

.choice-group {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.55rem;
}

.choice {
  position: relative;
}

.choice input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.choice span {
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.55rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-soft);
  color: var(--muted);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 700;
  text-align: center;
}

.choice input:checked + span {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
}

.choice input:focus-visible + span {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.form-actions {
  margin-top: 1.15rem;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.55rem;
}

.results-column {
  min-width: 0;
  display: grid;
  gap: 1.25rem;
}

.summary-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.8rem;
}

.summary-card {
  min-width: 0;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--surface);
}

.summary-card.primary {
  border-color: color-mix(in srgb, var(--accent) 58%, var(--border));
  background: linear-gradient(145deg, var(--accent-soft), var(--surface) 68%);
}

.summary-label {
  margin-bottom: 0.35rem;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 700;
}

.summary-value {
  overflow-wrap: anywhere;
  color: var(--text);
  font-family: var(--font-mono);
  font-size: clamp(1.15rem, 2.5vw, 1.65rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1.15;
}

.summary-card.primary .summary-value {
  color: var(--accent);
}

.summary-meta {
  margin-top: 0.3rem;
  color: var(--muted);
  font-size: 0.72rem;
}

.result-panel {
  padding: 1.25rem;
}

.panel-heading {
  margin-bottom: 1rem;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.panel-heading h2 {
  margin-bottom: 0.2rem;
  font-size: 1.05rem;
  letter-spacing: -0.02em;
}

.panel-heading p {
  margin-bottom: 0;
  color: var(--muted);
  font-size: 0.8rem;
}

.panel-badge {
  padding: 0.28rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 700;
  white-space: nowrap;
}

.chart-layout {
  display: grid;
  grid-template-columns: minmax(160px, 0.6fr) minmax(0, 1.4fr);
  gap: 1.5rem;
  align-items: center;
}

.donut {
  width: 156px;
  aspect-ratio: 1;
  margin: 0 auto;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: conic-gradient(
    var(--principal) 0 var(--principal-percent, 50%),
    var(--interest) var(--principal-percent, 50%) 100%
  );
  position: relative;
}

.donut::after {
  content: "";
  position: absolute;
  inset: 24px;
  border-radius: 50%;
  background: var(--surface);
}

.donut-center {
  position: relative;
  z-index: 1;
  text-align: center;
}

.donut-center strong {
  display: block;
  font-family: var(--font-mono);
  font-size: 1.25rem;
}

.donut-center span {
  color: var(--muted);
  font-size: 0.68rem;
}

.legend-list {
  display: grid;
  gap: 0.8rem;
}

.legend-item {
  display: grid;
  grid-template-columns: 11px 1fr auto;
  gap: 0.65rem;
  align-items: center;
}

.legend-dot {
  width: 10px;
  height: 10px;
  border-radius: 3px;
}

.legend-dot.principal {
  background: var(--principal);
}

.legend-dot.interest {
  background: var(--interest);
}

.legend-name {
  color: var(--muted);
  font-size: 0.8rem;
}

.legend-value {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 800;
}

.legend-percent {
  color: var(--muted);
  font-size: 0.72rem;
}

.table-wrap {
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  max-height: 560px;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.78rem;
  font-variant-numeric: tabular-nums;
}

.data-table th,
.data-table td {
  padding: 0.62rem 0.72rem;
  border-bottom: 1px solid var(--border);
  text-align: right;
  white-space: nowrap;
}

.data-table th {
  position: sticky;
  top: 0;
  z-index: 1;
  background: var(--surface-raised);
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

.data-table th:first-child,
.data-table td:first-child,
.data-table th:nth-child(2),
.data-table td:nth-child(2),
.data-table th:nth-child(3),
.data-table td:nth-child(3) {
  text-align: left;
}

.data-table tbody tr:hover {
  background: color-mix(in srgb, var(--accent) 4%, transparent);
}

.data-table tbody tr:last-child td {
  border-bottom: 0;
}

.phase-tag {
  display: inline-flex;
  padding: 0.12rem 0.42rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.68rem;
  font-weight: 800;
}

.phase-tag.grace {
  background: color-mix(in srgb, var(--warning) 15%, transparent);
  color: var(--warning);
}

.tabs {
  display: inline-flex;
  padding: 0.2rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface-soft);
}

.tab {
  padding: 0.38rem 0.72rem;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  font-size: 0.76rem;
  font-weight: 800;
}

.tab.active {
  background: var(--surface-raised);
  color: var(--text);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.16);
}

.rate-change {
  color: var(--danger);
  font-weight: 800;
}

.rate-change.zero {
  color: var(--muted);
}

.info-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
}

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

.info-item strong {
  display: block;
  margin-bottom: 0.2rem;
  font-size: 0.8rem;
}

.info-item span {
  color: var(--muted);
  font-size: 0.75rem;
}

.disclaimer {
  margin: 0 0 3.5rem;
  padding: 1.1rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--surface);
  color: var(--muted);
  font-size: 0.8rem;
}

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

.disclaimer ul {
  margin: 0.6rem 0 0;
  padding-left: 1.2rem;
}

.disclaimer li + li {
  margin-top: 0.35rem;
}

.footer {
  padding: 1.5rem 0 2.5rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.76rem;
  text-align: center;
}

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

@media (max-width: 1050px) {
  .summary-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 820px) {
  .hero {
    grid-template-columns: 1fr;
    align-items: start;
  }

  .hero-note {
    max-width: 620px;
  }

  .calculator-layout {
    grid-template-columns: 1fr;
  }

  .form-panel {
    position: static;
  }

  .chart-layout,
  .info-strip {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 520px) {
  .container,
  .topbar-inner {
    width: min(100% - 1.2rem, var(--max-width));
  }

  .hero {
    padding-top: 2.2rem;
  }

  .summary-grid,
  .field-grid,
  .choice-group {
    grid-template-columns: 1fr;
  }

  .field-wide {
    grid-column: auto;
  }

  .result-panel,
  .form-panel {
    padding: 1rem;
  }

  .form-actions {
    grid-template-columns: 1fr;
  }
}

@media print {
  :root {
    --bg: #fff;
    --surface: #fff;
    --surface-soft: #fff;
    --surface-raised: #eee;
    --text: #111;
    --muted: #555;
    --border: #ccc;
  }

  body {
    background: #fff;
  }

  .topbar,
  .action-row,
  .skip-link,
  .tabs,
  .footer {
    display: none !important;
  }

  .hero {
    padding: 1rem 0;
  }

  .calculator-layout {
    grid-template-columns: 1fr;
  }

  .form-panel {
    position: static;
    box-shadow: none;
  }

  .panel,
  .summary-card {
    box-shadow: none;
    break-inside: avoid;
  }

  .table-wrap {
    max-height: none;
    overflow: visible;
  }
}