/* layout.css - Bố cục Sidebar, Header và Khu vực chính */
.app-shell {
  display: flex;
  min-height: 100vh;
}
.sidebar {
  width: var(--sidebar-width);
  background: var(--bg-surface);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 40;
  transition: transform 0.25s ease;
}
.sidebar-brand {
  height: var(--header-height);
  padding: 0 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  border-bottom: 1px solid var(--border-color);
}
.brand-logo {
  width: 38px;
  height: 38px;
  border-radius: 10px;
  background: var(--gradient-brand);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 1.05rem;
  box-shadow: 0 4px 10px rgba(79, 70, 229, 0.3);
  flex-shrink: 0;
}
.brand-text h1 {
  font-size: 0.98rem;
  font-weight: 700;
  line-height: 1.2;
}
.brand-text span {
  font-size: 0.75rem;
  color: var(--text-muted);
}
.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}
.nav-section-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  padding: 0.75rem 0.75rem 0.35rem;
}
.nav-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.9rem;
  transition: all 0.18s ease;
  width: 100%;
  text-align: left;
}
.nav-item-left {
  display: flex;
  align-items: center;
  gap: 0.7rem;
}
.nav-item svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}
.nav-item:hover {
  background: var(--bg-elevated);
  color: var(--text-primary);
}
.nav-item.active {
  background: var(--primary-50);
  color: var(--primary-600);
  font-weight: 600;
}
.nav-badge {
  font-size: 0.72rem;
  padding: 0.12rem 0.5rem;
  border-radius: 999px;
  background: var(--bg-elevated);
  color: var(--text-muted);
  font-weight: 600;
}
.nav-item.active .nav-badge {
  background: var(--primary-100);
  color: var(--primary-600);
}
.sidebar-footer {
  padding: 0.9rem 1rem;
  border-top: 1px solid var(--border-color);
  background: var(--bg-elevated);
  font-size: 0.78rem;
}
.main-wrapper {
  flex: 1;
  margin-left: var(--sidebar-width);
  display: flex;
  flex-direction: column;
  min-width: 0;
}
.top-header {
  height: var(--header-height);
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  position: sticky;
  top: 0;
  z-index: 30;
}
.header-left {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex: 1;
  max-width: 520px;
}
.mobile-menu-btn {
  display: none;
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
}
.header-search {
  position: relative;
  flex: 1;
}
.header-search input {
  width: 100%;
  background: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: 999px;
  padding: 0.48rem 1rem 0.48rem 2.35rem;
  font-size: 0.875rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.header-search input:focus {
  border-color: var(--primary-500);
  box-shadow: 0 0 0 3px var(--primary-100);
  background: var(--bg-surface);
}
.header-search svg {
  position: absolute;
  left: 0.85rem;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  color: var(--text-muted);
}
.header-right {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}
.header-progress-pill {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.35rem 0.85rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 600;
}
.streak-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.75rem;
  background: var(--warning-50);
  color: var(--warning-600);
  border: 1px solid var(--warning-100);
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 700;
}
.icon-btn {
  width: 38px;
  height: 38px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  transition: all 0.18s;
}
.icon-btn:hover {
  border-color: var(--primary-500);
  color: var(--primary-600);
  background: var(--primary-50);
}
.main-content {
  flex: 1;
  padding: 1.5rem;
  max-width: 1400px;
  width: 100%;
  margin: 0 auto;
}
.sidebar-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.5);
  z-index: 35;
}