:root {
  --color-bg: #f4f6fb;
  --color-surface: #ffffff;
  --color-border: #e5e9f2;
  --color-text: #101828;
  --color-text-muted: #667085;
  --color-text-subtle: #98a2b3;

  --color-primary: #4f46e5;
  --color-primary-dark: #4338ca;
  --color-primary-soft: #eef2ff;

  --color-success: #12b76a;
  --color-warning: #f79009;
  --color-danger: #f04438;

  --sidebar-bg: #101828;
  --sidebar-text: #cbd5e1;
  --sidebar-text-muted: #8895ab;
  --sidebar-active-bg: rgba(79, 70, 229, 0.28);
  --sidebar-active-text: #ffffff;
  --sidebar-width: 248px;

  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 18px;

  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.05);
  --shadow-md: 0 2px 8px rgba(16, 24, 40, 0.06), 0 1px 2px rgba(16, 24, 40, 0.04);
  --shadow-lg: 0 12px 28px rgba(16, 24, 40, 0.10);

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
  text-decoration: none;
}

.muted {
  color: var(--color-text-muted);
}

/* ---------- Shell ---------- */

.app-shell {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  min-height: 100vh;
}

.mobile-topbar {
  display: none;
}

/* ---------- Sidebar ---------- */

.sidebar {
  background: var(--sidebar-bg);
  color: var(--sidebar-text);
  padding: 20px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.sidebar-brand {
  color: #ffffff;
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: -0.01em;
  padding: 8px 10px 22px;
}

.sidebar-nav {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.nav-item,
.nav-group-label {
  display: block;
  padding: 9px 12px;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--sidebar-text);
}

.nav-item:hover {
  background: rgba(255, 255, 255, 0.06);
  color: #ffffff;
}

.nav-item.active {
  background: var(--sidebar-active-bg);
  color: var(--sidebar-active-text);
  font-weight: 600;
}

.nav-group {
  margin-top: 2px;
}

.nav-group-label {
  color: var(--sidebar-text-muted);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding-bottom: 4px;
  padding-top: 12px;
}

.nav-group-label.active {
  color: #ffffff;
}

.nav-subitem {
  display: block;
  padding: 8px 12px 8px 22px;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  color: var(--sidebar-text);
}

.nav-subitem:hover {
  background: rgba(255, 255, 255, 0.06);
  color: #ffffff;
}

.nav-subitem.active {
  background: var(--sidebar-active-bg);
  color: var(--sidebar-active-text);
  font-weight: 600;
}

.sidebar-backdrop {
  display: none;
}

/* ---------- Content ---------- */

.content {
  padding: 36px 40px 64px;
  max-width: 1180px;
  width: 100%;
}

.hero h1 {
  font-size: 1.5rem;
  margin: 0 0 6px;
  letter-spacing: -0.01em;
}

.hero p {
  margin: 0 0 28px;
  font-size: 0.95rem;
}

/* ---------- Tiles (home) ---------- */

.tile-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-bottom: 40px;
}

.tile {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: 20px 22px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 10px;
  transition: box-shadow 0.15s ease, transform 0.15s ease, border-color 0.15s ease;
}

.tile:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
  border-color: var(--color-primary);
}

.tile-label {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.tile-value {
  font-size: 1.8rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.tile-value.coming-soon {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-subtle);
  text-transform: none;
  letter-spacing: normal;
}

/* ---------- Quick nav cards ---------- */

.quicknav h2 {
  font-size: 0.85rem;
  font-weight: 700;
  margin: 0 0 16px;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}

.nav-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 18px 20px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.15s ease, transform 0.15s ease;
}

.nav-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.nav-card h3 {
  margin: 0 0 6px;
  font-size: 0.95rem;
}

.nav-card p {
  margin: 0;
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

/* ---------- KPI row (dashboards) ---------- */

.kpi-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin: 4px 0 28px;
}

.kpi-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-left: 3px solid var(--color-primary);
  border-radius: var(--radius-lg);
  padding: 18px 20px;
  box-shadow: var(--shadow-sm);
}

.kpi-label {
  font-size: 0.78rem;
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  margin-bottom: 8px;
}

.kpi-value {
  font-size: 1.7rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.kpi-sub {
  font-size: 0.78rem;
  color: var(--color-text-muted);
  margin-top: 4px;
}

.kpi-card.status-good {
  border-left-color: var(--color-success);
}

.kpi-card.status-caution {
  border-left-color: var(--color-warning);
}

.kpi-card.status-concern {
  border-left-color: var(--color-danger);
}

.kpi-value.status-good {
  color: var(--color-success);
}

.kpi-value.status-caution {
  color: var(--color-warning);
}

.kpi-value.status-concern {
  color: var(--color-danger);
}

.kpi-card.clickable {
  cursor: pointer;
  transition: box-shadow 0.15s ease, transform 0.15s ease;
}

.kpi-card.clickable:hover,
.kpi-card.clickable:focus-visible {
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.kpi-drilldown-hint {
  font-size: 0.72rem;
  color: var(--color-primary);
  font-weight: 600;
  margin-top: 6px;
}

/* ---------- Drill-down modal ---------- */

.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 50;
  padding: 20px;
}

.modal-backdrop[hidden] {
  display: none;
}

.modal {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 560px;
  max-height: 80vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 22px;
  border-bottom: 1px solid var(--color-border);
}

.modal-header h2 {
  margin: 0;
  font-size: 1rem;
  font-weight: 700;
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.3rem;
  line-height: 1;
  cursor: pointer;
  color: var(--color-text-muted);
  padding: 4px 8px;
  border-radius: var(--radius-md);
}

.modal-close:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

.modal-body {
  padding: 12px 22px 22px;
  overflow-y: auto;
}

.modal-summary {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin: 0 0 14px;
}

.cohort-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.cohort-table th {
  text-align: left;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--color-text-muted);
  padding: 6px 8px;
  border-bottom: 1px solid var(--color-border);
}

.cohort-table td {
  padding: 8px;
  border-bottom: 1px solid var(--color-border);
}

.cohort-status {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 999px;
}

.cohort-status.retained {
  background: rgba(18, 183, 106, 0.12);
  color: var(--color-success);
}

.cohort-status.departed {
  background: rgba(240, 68, 56, 0.12);
  color: var(--color-danger);
}

/* ---------- Charts ---------- */

.chart-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 8px;
}

.chart-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: 22px;
  box-shadow: var(--shadow-sm);
}

.chart-card h3 {
  margin: 0 0 16px;
  font-size: 0.88rem;
  font-weight: 600;
}

.chart-card canvas {
  max-height: 280px;
}

.chart-card.wide {
  grid-column: 1 / -1;
}

.chart-hint {
  margin: 10px 0 0;
  font-size: 0.72rem;
  color: var(--color-text-muted);
  text-align: center;
}

/* ---------- Coming soon ---------- */

.coming-soon-page {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: 56px 32px;
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.coming-soon-page h1 {
  margin: 0 0 8px;
  font-size: 1.3rem;
}

.coming-soon-page p {
  margin: 0 0 20px;
}

.badge {
  display: inline-block;
  background: var(--color-primary-soft);
  color: var(--color-primary-dark);
  font-size: 0.78rem;
  font-weight: 700;
  padding: 6px 16px;
  border-radius: 999px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

/* ---------- Mobile nav toggle button ---------- */

.nav-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  width: 36px;
  height: 36px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  height: 2px;
  margin: 0 7px;
  background: var(--color-text);
}

/* ---------- Responsive ---------- */

@media (max-width: 960px) {
  .tile-grid,
  .card-grid,
  .kpi-row {
    grid-template-columns: repeat(2, 1fr);
  }

  .chart-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .mobile-topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 16px;
    background: var(--sidebar-bg);
    color: #ffffff;
    position: sticky;
    top: 0;
    z-index: 20;
  }

  .mobile-topbar .brand {
    font-weight: 700;
    font-size: 0.95rem;
  }

  .mobile-topbar .nav-toggle {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255, 255, 255, 0.15);
  }

  .mobile-topbar .nav-toggle span {
    background: #ffffff;
  }

  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    width: 260px;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    z-index: 30;
    overflow-y: auto;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.4);
    z-index: 25;
  }

  .sidebar-backdrop.open {
    display: block;
  }

  .content {
    padding: 24px 18px 48px;
  }

  .tile-grid,
  .card-grid,
  .kpi-row {
    grid-template-columns: 1fr;
  }
}