:root {
    --sidebar-width: 260px;
    --sidebar-collapsed: 72px;
    --topbar-height: 60px;
    --primary: #4f46e5;
    --primary-light: #818cf8;
    --primary-dark: #3730a3;
    --primary-bg: #eef2ff;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #06b6d4;
    --bg-body: #f1f5f9;
    --bg-card: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --bg-body: #0f172a;
    --bg-card: #1e293b;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: #334155;
    --primary-bg: #1e1b4b;
}

* { box-sizing: border-box; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-body);
    color: var(--text-primary);
    margin: 0;
    overflow-x: hidden;
}

.app-wrapper {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background: linear-gradient(180deg, #1e1b4b 0%, #312e81 100%);
    color: #fff;
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    z-index: 1040;
    display: flex;
    flex-direction: column;
    transition: var(--transition);
    overflow: hidden;
}

.sidebar.collapsed {
    width: var(--sidebar-collapsed);
}

.sidebar.collapsed .logo-text,
.sidebar.collapsed .nav-section-title,
.sidebar.collapsed .nav-link span,
.sidebar.collapsed .admin-detail,
.sidebar.collapsed .btn-logout {
    display: none;
}

.sidebar.collapsed .nav-link {
    justify-content: center;
    padding: 12px;
}

.sidebar-header {
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    border-bottom: 1px solid rgba(255,255,255,0.1);
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: rgba(255,255,255,0.15);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    flex-shrink: 0;
}

.logo-text h5 {
    margin: 0;
    font-weight: 700;
    font-size: 1rem;
}

.logo-text small {
    opacity: 0.6;
    font-size: 0.7rem;
}

.sidebar-nav {
    flex: 1;
    padding: 16px 12px;
    overflow-y: auto;
}

.nav-section-title {
    font-size: 0.65rem;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    opacity: 0.4;
    padding: 12px 12px 6px;
    font-weight: 600;
}

.sidebar-nav .nav-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    color: rgba(255,255,255,0.7);
    text-decoration: none;
    border-radius: var(--radius-sm);
    margin-bottom: 2px;
    transition: var(--transition);
    font-size: 0.875rem;
    font-weight: 500;
}

.sidebar-nav .nav-link:hover {
    background: rgba(255,255,255,0.1);
    color: #fff;
}

.sidebar-nav .nav-link.active {
    background: rgba(255,255,255,0.15);
    color: #fff;
    box-shadow: 0 0 0 1px rgba(255,255,255,0.1);
}

.sidebar-nav .nav-link i {
    font-size: 1.1rem;
    width: 22px;
    text-align: center;
}

.sidebar-footer {
    padding: 16px;
    border-top: 1px solid rgba(255,255,255,0.1);
}

.admin-info {
    display: flex;
    align-items: center;
    gap: 10px;
}

.admin-avatar {
    font-size: 1.8rem;
    opacity: 0.8;
}

.admin-detail {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.admin-name {
    font-size: 0.85rem;
    font-weight: 600;
}

.admin-role {
    font-size: 0.7rem;
    opacity: 0.5;
}

.btn-logout {
    color: rgba(255,255,255,0.5);
    font-size: 1.1rem;
    transition: var(--transition);
}

.btn-logout:hover {
    color: #ef4444;
}

/* Main Content */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    transition: var(--transition);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.sidebar.collapsed ~ .main-content,
body.sidebar-collapsed .main-content {
    margin-left: var(--sidebar-collapsed);
}

/* Top Bar */
.top-bar {
    height: var(--topbar-height);
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    position: sticky;
    top: 0;
    z-index: 1030;
    box-shadow: var(--shadow-sm);
}

.top-bar-left {
    display: flex;
    align-items: center;
    gap: 16px;
}

.top-bar-right {
    display: flex;
    align-items: center;
    gap: 8px;
}

.top-bar-item {
    padding: 0 8px;
}

.sidebar-toggle {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 4px;
}

.breadcrumb {
    font-size: 0.875rem;
}

.breadcrumb-item a {
    color: var(--primary);
    text-decoration: none;
}

.badge-notification {
    position: absolute;
    top: 2px;
    right: 2px;
    width: 16px;
    height: 16px;
    background: var(--danger);
    color: #fff;
    border-radius: 50%;
    font-size: 0.6rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.notification-dropdown {
    width: 320px;
    border: none;
    box-shadow: var(--shadow-lg);
    border-radius: var(--radius);
    padding: 0;
}

.notification-dropdown .dropdown-header {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border-color);
    font-weight: 600;
}

.notification-dropdown .dropdown-item {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border-color);
}

.notification-icon {
    width: 36px;
    height: 36px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 12px;
    flex-shrink: 0;
}

/* Content Area */
.content-area {
    padding: 24px;
    flex: 1;
}

/* Cards */
.stat-card {
    background: var(--bg-card);
    border-radius: var(--radius);
    padding: 24px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

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

.stat-card .stat-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
}

.stat-card .stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.2;
}

.stat-card .stat-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.stat-card .stat-change {
    font-size: 0.75rem;
    font-weight: 600;
}

.card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.card-header {
    background: transparent;
    border-bottom: 1px solid var(--border-color);
    padding: 16px 20px;
    font-weight: 600;
    font-size: 0.95rem;
}

/* Tables */
.table-container {
    background: var(--bg-card);
    border-radius: var(--radius);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.table {
    margin-bottom: 0;
}

.table thead th {
    background: #f8fafc;
    border-bottom: 2px solid var(--border-color);
    font-weight: 600;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
    padding: 12px 16px;
    white-space: nowrap;
}

[data-theme="dark"] .table thead th {
    background: #1a2332;
}

.table tbody td {
    padding: 14px 16px;
    vertical-align: middle;
    font-size: 0.875rem;
    border-bottom: 1px solid var(--border-color);
}

.table tbody tr:hover {
    background: rgba(79, 70, 229, 0.02);
}

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

/* Badges */
.badge-status {
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.3px;
}

.badge-pass {
    background: #d1fae5;
    color: #065f46;
}

.badge-fail {
    background: #fee2e2;
    color: #991b1b;
}

.badge-pending {
    background: #fef3c7;
    color: #92400e;
}

.badge-active {
    background: #dbeafe;
    color: #1e40af;
}

.badge-inactive {
    background: #f1f5f9;
    color: #64748b;
}

/* Buttons */
.btn-primary {
    background: var(--primary);
    border-color: var(--primary);
}

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

.btn-action {
    width: 32px;
    height: 32px;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    background: var(--bg-card);
    color: var(--text-secondary);
    transition: var(--transition);
}

.btn-action:hover {
    background: var(--primary-bg);
    color: var(--primary);
    border-color: var(--primary-light);
}

.btn-action.danger:hover {
    background: #fef2f2;
    color: var(--danger);
    border-color: #fca5a5;
}

/* Forms */
.form-control, .form-select {
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    padding: 8px 14px;
    font-size: 0.875rem;
    transition: var(--transition);
}

.form-control:focus, .form-select:focus {
    border-color: var(--primary-light);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.search-box {
    position: relative;
}

.search-box .bi-search {
    position: absolute;
    left: 14px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

.search-box input {
    padding-left: 40px;
}

/* Pagination */
.pagination .page-link {
    border-radius: var(--radius-sm);
    margin: 0 2px;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.85rem;
    padding: 6px 12px;
}

.pagination .page-item.active .page-link {
    background: var(--primary);
    border-color: var(--primary);
}

/* Progress bars */
.progress {
    height: 6px;
    border-radius: 3px;
    background: #e2e8f0;
}

/* Chart containers */
.chart-container {
    position: relative;
    height: 300px;
}

/* Animations */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.animate-in {
    animation: fadeInUp 0.4s ease-out;
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    .sidebar.show {
        transform: translateX(0);
    }
    .main-content {
        margin-left: 0 !important;
    }
    .content-area {
        padding: 16px;
    }
}

/* Login page */
.login-wrapper {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 20px;
}

.login-card {
    background: #fff;
    border-radius: 20px;
    padding: 48px 40px;
    width: 100%;
    max-width: 420px;
    box-shadow: 0 25px 50px -12px rgba(0,0,0,0.25);
}

.login-card .login-icon {
    width: 64px;
    height: 64px;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    color: #fff;
    margin: 0 auto 24px;
}

.login-card h3 {
    text-align: center;
    font-weight: 700;
    margin-bottom: 8px;
}

.login-card .subtitle {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: 32px;
}

/* Modal */
.modal-content {
    border: none;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
}

.modal-header {
    border-bottom: 1px solid var(--border-color);
}

.modal-footer {
    border-top: 1px solid var(--border-color);
}

/* Question type badges */
.q-type {
    font-size: 0.72rem;
    padding: 3px 8px;
    border-radius: 6px;
    font-weight: 600;
}

.q-type-single { background: #dbeafe; color: #1e40af; }
.q-type-multi { background: #fce7f3; color: #9d174d; }
.q-type-judge { background: #d1fae5; color: #065f46; }

/* Difficulty stars */
.difficulty-stars {
    color: #f59e0b;
    font-size: 0.8rem;
}

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: #94a3b8; }