:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --bg: #0f172a;
    --bg-light: #1e293b;
    --card: #1e293b;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: #334155;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

.hidden {
    display: none !important;
}

/* Login Screen */
.login-screen {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
}

.login-card {
    background: var(--card);
    padding: 40px;
    border-radius: 16px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
    width: 90%;
    max-width: 400px;
    border: 1px solid var(--border);
}

.login-card h1 {
    font-size: 28px;
    margin-bottom: 8px;
    text-align: center;
}

.subtitle {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: 30px;
    font-size: 14px;
}

.login-card input {
    width: 100%;
    padding: 14px;
    margin-bottom: 16px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: var(--bg);
    color: var(--text);
    font-size: 15px;
    outline: none;
    transition: border-color 0.2s;
}

.login-card input:focus {
    border-color: var(--primary);
}

.warning {
    text-align: center;
    color: var(--warning);
    font-size: 13px;
    margin-top: 20px;
}

/* Buttons */
.btn-primary {
    width: 100%;
    padding: 14px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}

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

.btn-danger {
    padding: 10px 16px;
    background: var(--danger);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
}

.btn-danger:hover {
    opacity: 0.9;
}

.btn-warning {
    padding: 10px 16px;
    background: var(--warning);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
}

.btn-warning:hover {
    opacity: 0.9;
}

.btn-logout {
    width: 100%;
    padding: 12px;
    background: transparent;
    color: var(--danger);
    border: 1px solid var(--danger);
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-logout:hover {
    background: var(--danger);
    color: white;
}

/* Dashboard Layout */
#adminDashboard {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: 260px;
    background: var(--card);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
}

.logo {
    padding: 24px 20px;
    border-bottom: 1px solid var(--border);
}

.logo h2 {
    font-size: 18px;
    font-weight: 700;
}

.nav-menu {
    flex: 1;
    padding: 20px 0;
}

.nav-item {
    display: block;
    padding: 14px 20px;
    color: var(--text-muted);
    text-decoration: none;
    transition: all 0.2s;
    border-left: 3px solid transparent;
}

.nav-item:hover {
    background: rgba(37, 99, 235, 0.1);
    color: var(--text);
}

.nav-item.active {
    background: rgba(37, 99, 235, 0.15);
    color: var(--primary);
    border-left-color: var(--primary);
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border);
}

/* Main Content */
.main-content {
    flex: 1;
    margin-left: 260px;
    padding: 0;
}

.header {
    background: var(--card);
    padding: 24px 32px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header h1 {
    font-size: 24px;
    font-weight: 700;
}

.user-info {
    color: var(--text-muted);
    font-size: 14px;
}

/* Sections */
.section {
    display: none;
    padding: 32px;
}

.section.active {
    display: block;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.stat-card {
    background: var(--card);
    padding: 24px;
    border-radius: 12px;
    border: 1px solid var(--border);
    display: flex;
    align-items: center;
    gap: 16px;
}

.stat-icon {
    font-size: 36px;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(37, 99, 235, 0.1);
    border-radius: 12px;
}

.stat-info h3 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 4px;
}

.stat-info p {
    color: var(--text-muted);
    font-size: 14px;
}

/* Recent Activity */
.recent-activity {
    background: var(--card);
    padding: 24px;
    border-radius: 12px;
    border: 1px solid var(--border);
}

.recent-activity h2 {
    font-size: 18px;
    margin-bottom: 20px;
}

/* Section Header */
.section-header {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
}

.search-input {
    flex: 1;
    padding: 12px 16px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: var(--bg);
    color: var(--text);
    font-size: 15px;
    outline: none;
}

.search-input:focus {
    border-color: var(--primary);
}

/* Table Container */
.table-container {
    background: var(--card);
    border-radius: 12px;
    border: 1px solid var(--border);
    overflow: hidden;
}

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

.data-table thead {
    background: var(--bg-light);
}

.data-table th {
    padding: 16px;
    text-align: left;
    font-weight: 600;
    font-size: 14px;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}

.data-table td {
    padding: 16px;
    border-bottom: 1px solid var(--border);
}

.data-table tbody tr:last-child td {
    border-bottom: none;
}

.data-table tbody tr:hover {
    background: rgba(37, 99, 235, 0.05);
}

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

/* User Detail Card */
.user-detail-card {
    background: var(--card);
    padding: 24px;
    border-radius: 12px;
    border: 1px solid var(--border);
}

.user-detail-card h3 {
    font-size: 18px;
    margin-bottom: 20px;
}

.user-detail-card h4 {
    font-size: 16px;
    margin-top: 24px;
    margin-bottom: 12px;
}

.detail-row {
    display: flex;
    justify-content: space-between;
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
}

.detail-row:last-child {
    border-bottom: none;
}

.detail-row .label {
    color: var(--text-muted);
    font-weight: 600;
}

.detail-row .value {
    color: var(--text);
}

.badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 600;
}

.badge-success {
    background: rgba(16, 185, 129, 0.2);
    color: var(--success);
}

.badge-warning {
    background: rgba(245, 158, 11, 0.2);
    color: var(--warning);
}

.badge-danger {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger);
}

.course-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 20px;
}

.course-item {
    padding: 12px;
    background: var(--bg);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.action-buttons {
    display: flex;
    gap: 12px;
    margin-top: 24px;
}

.loading {
    text-align: center;
    padding: 40px;
    color: var(--text-muted);
}

/* Toast */
.toast {
    position: fixed;
    bottom: 30px;
    right: 30px;
    padding: 16px 24px;
    border-radius: 10px;
    background: var(--card);
    border: 1px solid var(--border);
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
    z-index: 9999;
    transition: opacity 0.3s;
}

.toast.success {
    border-color: var(--success);
    background: rgba(16, 185, 129, 0.1);
}

.toast.error {
    border-color: var(--danger);
    background: rgba(239, 68, 68, 0.1);
}

.toast.info {
    border-color: var(--primary);
    background: rgba(37, 99, 235, 0.1);
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .sidebar {
        width: 100%;
        position: relative;
        height: auto;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .header {
        padding: 20px;
    }
    
    .section {
        padding: 20px;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .section-header {
        flex-direction: column;
    }
    
    .action-buttons {
        flex-direction: column;
    }
}