:root {
    --primary: #4f46e5;
    --primary-dark: #4338ca;
    --primary-light: #e0e7ff;
    --success: #22c55e;
    --warning: #f59e0b;
    --danger: #ef4444;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --radius: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.07);
    --transition: 0.2s ease;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--gray-50);
    color: var(--gray-800);
    line-height: 1.6;
    font-size: 15px;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-dark); }

/* Layout */
.layout { display: flex; min-height: 100vh; }

.sidebar {
    width: 260px;
    background: var(--gray-900);
    color: #fff;
    padding: 0;
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    overflow-y: auto;
    z-index: 100;
    display: flex;
    flex-direction: column;
}

.sidebar-brand {
    padding: 24px 20px;
    font-size: 20px;
    font-weight: 700;
    letter-spacing: -0.5px;
    border-bottom: 1px solid rgba(255,255,255,0.1);
}

.sidebar-brand span { color: var(--primary-light); }

.sidebar-nav { flex: 1; padding: 16px 0; }

.sidebar-nav a {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 20px;
    color: var(--gray-400);
    font-size: 14px;
    transition: var(--transition);
    border-left: 3px solid transparent;
}

.sidebar-nav a:hover,
.sidebar-nav a.active {
    color: #fff;
    background: rgba(255,255,255,0.05);
    border-left-color: var(--primary);
}

.sidebar-nav a svg { width: 20px; height: 20px; flex-shrink: 0; }

.sidebar-footer {
    padding: 16px 20px;
    border-top: 1px solid rgba(255,255,255,0.1);
    font-size: 13px;
    color: var(--gray-500);
}

.main-content {
    flex: 1;
    margin-left: 260px;
    padding: 32px;
    min-height: 100vh;
}

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
}

.topbar h1 {
    font-size: 24px;
    font-weight: 700;
    color: var(--gray-900);
}

.topbar-actions { display: flex; gap: 12px; align-items: center; }

/* Cards */
.card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 24px;
    margin-bottom: 24px;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
}

.card-header h2 {
    font-size: 16px;
    font-weight: 600;
    color: var(--gray-800);
}

/* Stat cards */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.stat-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 20px;
}

.stat-card .stat-label {
    font-size: 13px;
    color: var(--gray-500);
    margin-bottom: 4px;
}

.stat-card .stat-value {
    font-size: 28px;
    font-weight: 700;
    color: var(--gray-900);
}

.stat-card .stat-sub {
    font-size: 12px;
    color: var(--gray-400);
    margin-top: 4px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 500;
    border: none;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    line-height: 1.4;
}

.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); color: #fff; }

.btn-success { background: var(--success); color: #fff; }
.btn-success:hover { background: #16a34a; color: #fff; }

.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { background: #dc2626; color: #fff; }

.btn-outline {
    background: transparent;
    color: var(--gray-600);
    border: 1px solid var(--gray-300);
}
.btn-outline:hover { background: var(--gray-100); color: var(--gray-800); }

.btn-sm { padding: 5px 10px; font-size: 13px; }
.btn-lg { padding: 12px 24px; font-size: 16px; }

/* Forms */
.form-group { margin-bottom: 20px; }

.form-group label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 6px;
}

.form-control {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 14px;
    transition: var(--transition);
    background: #fff;
    color: var(--gray-800);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-light);
}

select.form-control { appearance: auto; }
textarea.form-control { resize: vertical; min-height: 80px; }

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.form-hint {
    font-size: 12px;
    color: var(--gray-400);
    margin-top: 4px;
}

/* Tables */
.table-wrap { overflow-x: auto; }

table {
    width: 100%;
    border-collapse: collapse;
}

table th, table td {
    padding: 12px 16px;
    text-align: left;
    border-bottom: 1px solid var(--gray-200);
    font-size: 14px;
}

table th {
    font-weight: 600;
    color: var(--gray-600);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    background: var(--gray-50);
}

table tr:hover td { background: var(--gray-50); }

/* Badges */
.badge {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
}

.badge-success { background: #dcfce7; color: #166534; }
.badge-warning { background: #fef3c7; color: #92400e; }
.badge-danger { background: #fee2e2; color: #991b1b; }
.badge-info { background: var(--primary-light); color: var(--primary-dark); }
.badge-gray { background: var(--gray-200); color: var(--gray-600); }

/* Alerts */
.alert {
    padding: 12px 16px;
    border-radius: var(--radius);
    margin-bottom: 20px;
    font-size: 14px;
}

.alert-success { background: #dcfce7; color: #166534; border: 1px solid #bbf7d0; }
.alert-danger { background: #fee2e2; color: #991b1b; border: 1px solid #fecaca; }
.alert-warning { background: #fef3c7; color: #92400e; border: 1px solid #fde68a; }
.alert-info { background: var(--primary-light); color: var(--primary-dark); border: 1px solid #c7d2fe; }

/* Progress bar */
.progress-bar {
    height: 8px;
    background: var(--gray-200);
    border-radius: 4px;
    overflow: hidden;
}

.progress-bar .progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 4px;
    transition: width 0.3s ease;
}

.progress-bar.success .progress-fill { background: var(--success); }

/* Auth page */
.auth-wrapper {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    background: linear-gradient(135deg, var(--gray-900) 0%, var(--gray-800) 100%);
}

.auth-card {
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
    padding: 40px;
    width: 100%;
    max-width: 420px;
}

.auth-card h1 {
    font-size: 24px;
    font-weight: 700;
    text-align: center;
    margin-bottom: 8px;
    color: var(--gray-900);
}

.auth-card .subtitle {
    text-align: center;
    color: var(--gray-500);
    font-size: 14px;
    margin-bottom: 32px;
}

.auth-card .btn { width: 100%; justify-content: center; padding: 12px; }

.auth-tabs {
    display: flex;
    border-bottom: 2px solid var(--gray-200);
    margin-bottom: 24px;
}

.auth-tabs button {
    flex: 1;
    padding: 10px;
    background: none;
    border: none;
    font-size: 14px;
    font-weight: 600;
    color: var(--gray-400);
    cursor: pointer;
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: var(--transition);
}

.auth-tabs button.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

.auth-footer {
    text-align: center;
    margin-top: 24px;
    font-size: 13px;
    color: var(--gray-500);
}

/* Empty state */
.empty-state {
    text-align: center;
    padding: 48px 20px;
    color: var(--gray-500);
}

.empty-state svg { width: 48px; height: 48px; color: var(--gray-300); margin-bottom: 16px; }
.empty-state h3 { font-size: 16px; color: var(--gray-600); margin-bottom: 8px; }
.empty-state p { font-size: 14px; margin-bottom: 20px; }

/* Pagination */
.pagination {
    display: flex;
    gap: 4px;
    justify-content: center;
    margin-top: 24px;
}

.pagination a, .pagination span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius);
    font-size: 14px;
    color: var(--gray-600);
    border: 1px solid var(--gray-200);
    transition: var(--transition);
}

.pagination a:hover { background: var(--gray-100); }
.pagination .active {
    background: var(--primary);
    color: #fff;
    border-color: var(--primary);
}

/* Utility */
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-muted { color: var(--gray-500); }
.text-small { font-size: 13px; }
.text-success { color: var(--success); }
.text-danger { color: var(--danger); }
.mt-1 { margin-top: 8px; }
.mt-2 { margin-top: 16px; }
.mt-3 { margin-top: 24px; }
.mb-1 { margin-bottom: 8px; }
.mb-2 { margin-bottom: 16px; }
.mb-3 { margin-bottom: 24px; }
.d-flex { display: flex; }
.gap-2 { gap: 16px; }
.align-center { align-items: center; }
.justify-between { justify-content: space-between; }
.w-full { width: 100%; }

/* Responsive */
@media (max-width: 768px) {
    .sidebar { display: none; }
    .main-content { margin-left: 0; padding: 16px; }
    .form-row { grid-template-columns: 1fr; }
    .stats-grid { grid-template-columns: 1fr 1fr; }
}

/* Tab indicator for content type icons */
.content-type-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: 6px;
    font-size: 14px;
    font-weight: 700;
}

.content-type-icon.text { background: #dbeafe; color: #1d4ed8; }
.content-type-icon.pdf { background: #fee2e2; color: #dc2626; }
.content-type-icon.ppt { background: #fef3c7; color: #d97706; }
.content-type-icon.video { background: #dcfce7; color: #16a34a; }

/* Dropdown */
.dropdown { position: relative; }
.dropdown-menu {
    position: absolute;
    right: 0;
    top: 100%;
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--gray-200);
    min-width: 160px;
    padding: 4px 0;
    display: none;
    z-index: 50;
}

.dropdown-menu.show { display: block; }

.dropdown-menu a {
    display: block;
    padding: 8px 16px;
    font-size: 13px;
    color: var(--gray-700);
}

.dropdown-menu a:hover { background: var(--gray-50); }

/* Course card grid */
.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.course-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: var(--transition);
}

.course-card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }

.course-card-cover {
    height: 140px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 32px;
    font-weight: 700;
}

.course-card-body { padding: 16px; }
.course-card-body h3 { font-size: 16px; font-weight: 600; margin-bottom: 8px; }
.course-card-body p { font-size: 13px; color: var(--gray-500); margin-bottom: 12px; }
.course-card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 16px;
    border-top: 1px solid var(--gray-100);
    font-size: 12px;
    color: var(--gray-500);
}