* { box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: var(--text-base);
  margin: 0;
  background: var(--surface-secondary);
  color: var(--foreground-primary);
  line-height: 1.5;
}

/* ---- App shell: fixed sidebar + fluid content ---- */
.app-shell {
  display: flex;
  min-height: 100vh;
}

.app-sidebar {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: 240px;
  display: flex;
  flex-direction: column;
  background: var(--surface-elevated);
  border-right: 1px solid var(--border-default);
  z-index: 200;
}

.sidebar-brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  height: 52px;
  padding: 0 var(--space-4);
  border-bottom: 1px solid var(--border-default);
  flex-shrink: 0;
}

.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border-radius: var(--radius-md);
  background: var(--accent-base);
  color: var(--foreground-inverse);
  font-weight: 700;
  font-size: var(--text-sm);
}

.brand-name {
  font-weight: 600;
  font-size: var(--text-base);
  color: var(--foreground-primary);
}

.app-sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-3) var(--space-2);
}

.nav-group { margin-bottom: var(--space-1); }

.nav-group-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--space-2) var(--space-3);
  background: none;
  border: none;
  cursor: pointer;
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--foreground-muted);
  border-radius: var(--radius-md);
}

.nav-group-title:hover { color: var(--foreground-secondary); }

.nav-chevron {
  width: 14px;
  height: 14px;
  transition: transform 0.15s;
}

.nav-group.collapsed .nav-chevron { transform: rotate(-90deg); }
.nav-group.collapsed .nav-group-items { display: none; }

.nav-group-items { margin-bottom: var(--space-2); }

.app-sidebar-nav a {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 7px var(--space-3);
  text-decoration: none;
  color: var(--foreground-secondary);
  font-size: var(--text-sm);
  border-radius: var(--radius-md);
  transition: background 0.12s, color 0.12s;
  white-space: nowrap;
}

.nav-group-flat { margin-bottom: var(--space-2); }

.app-sidebar-nav a:hover {
  background: var(--surface-hover);
  color: var(--foreground-primary);
}

.app-sidebar-nav a.active {
  background: var(--accent-bg);
  color: var(--accent-base);
  font-weight: 600;
}

.nav-icon {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.sidebar-footer {
  flex-shrink: 0;
  padding: var(--space-3);
  border-top: 1px solid var(--border-default);
}

.sidebar-email {
  display: block;
  font-size: var(--text-xs);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  margin-bottom: var(--space-2);
}

.sidebar-footer-actions {
  display: flex;
  gap: var(--space-2);
}

.sidebar-footer-actions .btn-secondary {
  flex: 1;
  justify-content: center;
}

.sidebar-overlay {
  display: none;
}

.app-content {
  flex: 1;
  min-width: 0;
  margin-left: 240px;
  display: flex;
  flex-direction: column;
}

.app-topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  height: 52px;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 0 var(--space-5);
  background: var(--surface-elevated);
  border-bottom: 1px solid var(--border-default);
}

.topbar-title {
  font-size: var(--text-lg);
  font-weight: 600;
  margin: 0;
  color: var(--foreground-primary);
}

#mobileNavToggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.4rem;
  line-height: 1;
  color: var(--foreground-primary);
  cursor: pointer;
  padding: var(--space-1);
}

main {
  flex: 1;
  padding: var(--space-5);
  min-width: 0;
}

@media (max-width: 1024px) {
  .app-content { margin-left: 0; }

  .app-sidebar {
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    box-shadow: var(--shadow-lg);
  }

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

  .sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.4);
    z-index: 150;
  }

  .app-shell.sidebar-open .sidebar-overlay { display: block; }

  #mobileNavToggle { display: block; }
}

@media (max-width: 600px) {
  main { padding: var(--space-4) var(--space-3); }
  .app-topbar { padding: 0 var(--space-3); }
}

/* ---- In-page secondary sidebar (used by pages with sub-tabs) ---- */
.sidebar-layout {
  display: flex;
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--surface-secondary);
}

.sidebar-nav {
  width: 160px;
  border-right: 1px solid var(--border-default);
  background: var(--surface-secondary);
  padding: 0.5rem 0;
  flex-shrink: 0;
}

.sidebar-nav button {
  display: block;
  width: 100%;
  text-align: left;
  padding: 0.6rem 1rem;
  background: none;
  border: none;
  border-right: 3px solid transparent;
  color: var(--foreground-secondary);
  cursor: pointer;
  font-size: 0.9rem;
}

.sidebar-nav button.active {
  background: var(--surface-primary);
  color: var(--accent-base);
  border-right-color: var(--accent-base);
  font-weight: 600;
}

.sidebar-content {
  flex: 1;
  padding: 1rem;
  min-width: 0;
}

@media (max-width: 600px) {
  .sidebar-layout { flex-direction: column; }
  .sidebar-nav {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid var(--border-default);
    display: flex;
    overflow-x: auto;
    padding: 0.25rem;
  }
  .sidebar-nav button {
    white-space: nowrap;
    border-right: none;
    border-bottom: 3px solid transparent;
  }
  .sidebar-nav button.active {
    border-right-color: transparent;
    border-bottom-color: var(--accent-base);
  }
}