:root {
  --nb-primary: #4F46E5;
  --nb-primary-dark: #3730A3;
  --nb-accent: #7C3AED;
  --nb-success: #10B981;
  --nb-warning: #F59E0B;
  --nb-danger: #EF4444;
  --nb-bg: #F5F6FA;
  --nb-radius: 14px;
}

body {
  background: var(--nb-bg);
  font-family: 'Segoe UI', system-ui, sans-serif;
}

/* Sidebar */
.nb-sidebar {
  min-height: 100vh;
  background: linear-gradient(180deg, var(--nb-primary), var(--nb-primary-dark));
  color: #fff;
  width: 260px;
  position: fixed;
  top: 0; left: 0; bottom: 0;
  overflow-y: auto;
  z-index: 1030;
}
.nb-sidebar .brand {
  font-weight: 700;
  font-size: 1.15rem;
  padding: 1.25rem 1.25rem 0.5rem;
}
.nb-sidebar a.nav-link {
  color: rgba(255,255,255,0.85);
  border-radius: 10px;
  margin: 2px 12px;
  padding: 0.6rem 1rem;
}
.nb-sidebar a.nav-link.active,
.nb-sidebar a.nav-link:hover {
  background: rgba(255,255,255,0.15);
  color: #fff;
}
.nb-content {
  margin-left: 260px;
  padding: 24px;
}
@media (max-width: 768px) {
  .nb-sidebar { transform: translateX(-100%); transition: transform .25s ease; }
  .nb-sidebar.show { transform: translateX(0); }
  .nb-content { margin-left: 0; }
}

/* Cards */
.nb-card {
  border: none;
  border-radius: var(--nb-radius);
  box-shadow: 0 2px 12px rgba(0,0,0,0.06);
}
.nb-stat-card {
  border-radius: var(--nb-radius);
  padding: 1.25rem;
  color: #fff;
}
.nb-stat-card.bg-purple { background: linear-gradient(135deg,#7C3AED,#4F46E5); }
.nb-stat-card.bg-green  { background: linear-gradient(135deg,#10B981,#059669); }
.nb-stat-card.bg-orange { background: linear-gradient(135deg,#F59E0B,#D97706); }
.nb-stat-card.bg-pink   { background: linear-gradient(135deg,#EC4899,#DB2777); }

/* Note cards (student browse view) */
.note-card {
  border-radius: var(--nb-radius);
  transition: transform .15s ease, box-shadow .15s ease;
  border: 1px solid #eee;
}
.note-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.08);
}
.note-icon { font-size: 2rem; }

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