:root {
  color-scheme: light;
  --bg: #f3f6fb;
  --panel: #ffffff;
  --panel-soft: #f8fafc;
  --text: #172033;
  --muted: #5f6c80;
  --border: #dbe4ee;
  --primary: #4f46e5;
  --primary-soft: #eef2ff;
  --success: #166534;
  --success-soft: #ecfdf5;
  --warning: #9a3412;
  --warning-soft: #fff7ed;
  --danger: #991b1b;
  --danger-soft: #fef2f2;
  --info: #1d4ed8;
  --info-soft: #eff6ff;
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
  --radius: 18px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Inter", sans-serif;
  background: linear-gradient(180deg, #eef3fb 0%, #f8fafc 100%);
  color: var(--text);
}

.app-shell {
  width: min(1180px, calc(100vw - 24px));
  margin: 0 auto;
  padding: 16px 0 48px;
}

.page-nav {
  display: flex;
  gap: 10px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.nav-btn {
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  border-radius: 999px;
  padding: 10px 16px;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.nav-btn.active {
  background: linear-gradient(135deg, #4f46e5, #6366f1);
  color: #fff;
  border-color: transparent;
}

.hero-card,
.card,
.notice {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-card {
  padding: 24px;
  margin-bottom: 14px;
  background: linear-gradient(135deg, #0f2027 0%, #203a43 48%, #2c5364 100%);
  color: #fff;
}

.hero-card h1 {
  margin: 8px 0 8px;
  font-size: clamp(1.8rem, 4vw, 2.6rem);
}

.hero-card p {
  margin: 0;
  color: rgba(255, 255, 255, 0.72);
}

.hero-badge {
  display: inline-flex;
  padding: 6px 12px;
  border-radius: 999px;
  background: rgba(100, 210, 255, 0.16);
  border: 1px solid rgba(100, 210, 255, 0.35);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-size: 0.72rem;
  font-weight: 700;
}

.notice {
  margin-bottom: 14px;
  padding: 14px 16px;
  font-size: 0.95rem;
  line-height: 1.5;
}

.notice.warning {
  background: linear-gradient(90deg, rgba(255, 243, 205, 0.7), rgba(255, 250, 235, 0.9));
}

.card {
  padding: 18px;
  margin-bottom: 14px;
}

.section-heading {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
}

.section-heading h2 {
  margin: 0;
  font-size: 1.1rem;
}

.section-heading p {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.form-stack,
.results-stack {
  display: grid;
  gap: 14px;
}

.grid {
  display: grid;
  gap: 14px;
}

.five-up {
  grid-template-columns: repeat(5, minmax(0, 1fr));
}

.four-up {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.field,
.info-tile {
  display: flex;
  flex-direction: column;
  gap: 8px;
  background: var(--panel-soft);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 14px;
}

.field span,
.toggle-field span {
  font-weight: 600;
}

.field small,
.muted {
  color: var(--muted);
  font-size: 0.84rem;
}

input[type="number"] {
  width: 100%;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid #c8d4e3;
  font-size: 1rem;
  font-family: "JetBrains Mono", monospace;
  color: var(--text);
  background: #fff;
}

input[type="number"]:focus {
  outline: 3px solid rgba(79, 70, 229, 0.18);
  border-color: var(--primary);
}

input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--primary);
}

.toggle-field {
  justify-content: center;
}

.toggle-row {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
}

.advanced-panel {
  display: grid;
  gap: 10px;
  background: #f8fbff;
  border: 1px dashed #bfd1eb;
  border-radius: 16px;
  padding: 16px;
}

.hidden {
  display: none !important;
}

.action-row {
  display: flex;
  justify-content: flex-start;
}

.primary-btn {
  border: none;
  border-radius: 14px;
  background: linear-gradient(135deg, #4f46e5, #6366f1);
  color: #fff;
  padding: 14px 22px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 10px 22px rgba(99, 102, 241, 0.28);
}

.primary-btn:hover {
  transform: translateY(-1px);
}

.metric-grid,
.comparison-grid,
.details-grid,
.reference-list,
.formula-grid {
  display: grid;
  gap: 14px;
}

.metric-grid {
  grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
}

.metric-box,
.result-card,
.reference-item {
  border: 1px solid var(--border);
  background: var(--panel-soft);
  border-radius: 16px;
  padding: 14px;
}

.metric-box .label,
.result-card .eyebrow {
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.74rem;
  font-weight: 700;
}

.metric-box .value {
  font-family: "JetBrains Mono", monospace;
  font-weight: 700;
  font-size: 1.2rem;
  margin-top: 8px;
}

.metric-box .unit,
.result-card .detail {
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 6px;
}

.comparison-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.details-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.result-card h3 {
  margin: 8px 0 8px;
  font-size: 1.05rem;
}

.result-card p {
  margin: 0;
  line-height: 1.5;
}

.result-card ul {
  margin: 10px 0 0;
  padding-left: 18px;
  color: var(--muted);
}

.tone-primary {
  background: var(--primary-soft);
  border-color: #c7d2fe;
}

.tone-success {
  background: var(--success-soft);
  border-color: #bbf7d0;
}

.tone-warning {
  background: var(--warning-soft);
  border-color: #fed7aa;
}

.tone-danger {
  background: var(--danger-soft);
  border-color: #fecaca;
}

.tone-info {
  background: var(--info-soft);
  border-color: #bfdbfe;
}

.reference-list {
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.formula-grid {
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
}

.reference-item p {
  margin: 8px 0 0;
  color: var(--muted);
}

.reference-item code {
  display: block;
  margin-top: 6px;
  padding: 8px 10px;
  background: #eef2ff;
  border: 1px solid #c7d2fe;
  border-radius: 10px;
  color: #312e81;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.83rem;
  overflow-wrap: anywhere;
}

.credits-card p:first-child {
  margin-top: 0;
}

@media (max-width: 960px) {
  .five-up,
  .four-up,
  .comparison-grid,
  .details-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .app-shell {
    width: min(100vw - 16px, 100%);
    padding-top: 8px;
  }

  .hero-card,
  .card,
  .notice {
    border-radius: 16px;
  }

  .five-up,
  .four-up,
  .comparison-grid,
  .details-grid,
  .reference-list,
  .formula-grid {
    grid-template-columns: 1fr;
  }

  .card {
    padding: 14px;
  }

  .page-nav {
    flex-direction: column;
  }

  .nav-btn {
    width: 100%;
  }

  .primary-btn {
    width: 100%;
  }
}