/**
 * Modern Design System - Quizz / Sinh Hoat Chuyen Mon
 * Responsive, Mobile-First, Accessible
 */

@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap');

:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #eff6ff;
    --primary-subtle: rgba(37, 99, 235, 0.08);
    --primary-gradient: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%);
    --primary-glow: rgba(37, 99, 235, 0.25);

    --secondary: #64748b;
    --secondary-light: #f1f5f9;
    --secondary-hover: #475569;

    --success: #10b981;
    --success-hover: #059669;
    --success-light: #ecfdf5;
    --success-subtle: rgba(16, 185, 129, 0.12);

    --warning: #f59e0b;
    --warning-hover: #d97706;
    --warning-light: #fffbeb;
    --warning-subtle: rgba(245, 158, 11, 0.12);

    --danger: #ef4444;
    --danger-hover: #dc2626;
    --danger-light: #fef2f2;
    --danger-subtle: rgba(239, 68, 68, 0.12);

    --info: #06b6d4;
    --info-light: #ecfeff;

    --dark: #0f172a;
    --dark-muted: #334155;
    --light: #f8fafc;
    --body-bg: #f8fafc;
    --card-bg: #ffffff;
    --text-dark: #0f172a;
    --text-main: #1e293b;
    --text-light: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --border-focus: #93c5fd;

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-full: 9999px;

    --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
    --shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.06), 0 1px 2px rgba(15, 23, 42, 0.04);
    --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.07), 0 2px 4px -2px rgba(15, 23, 42, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.04);
    --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.1), 0 8px 10px -6px rgba(15, 23, 42, 0.04);

    --sidebar-width: 256px;
    --topbar-height: 64px;
}

/* Base styling */
* {
    box-sizing: border-box;
}

body {
    background-color: var(--body-bg);
    color: var(--text-main);
    font-family: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    margin: 0;
    padding: 0;
    padding-left: var(--sidebar-width);
    transition: padding-left 0.25s ease;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Headings */
h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
    color: var(--text-dark);
    font-weight: 700;
    letter-spacing: -0.02em;
}

/* App Header for Mobile */
.mobile-appbar {
    display: none;
    position: sticky;
    top: 0;
    left: 0;
    right: 0;
    height: var(--topbar-height);
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1020;
    padding: 0 16px;
    align-items: center;
    justify-content: space-between;
}

.mobile-appbar .brand-title {
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--primary);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 8px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.mobile-appbar .menu-btn {
    width: 42px;
    height: 42px;
    border-radius: var(--radius-md);
    background: var(--primary-light);
    color: var(--primary);
    border: none;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.15rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.mobile-appbar .menu-btn:active {
    transform: scale(0.95);
    background: var(--primary-subtle);
}

/* Sidebar navigation */
.app-sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: var(--sidebar-width);
    height: 100vh;
    background: #ffffff;
    border-right: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    z-index: 1035;
    display: flex;
    flex-direction: column;
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.sidebar-header {
    height: var(--topbar-height);
    padding: 0 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header .brand {
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--primary);
    font-weight: 800;
    font-size: 1.05rem;
    text-decoration: none;
    letter-spacing: -0.01em;
}

.sidebar-header .brand .brand-icon {
    width: 38px;
    height: 38px;
    border-radius: var(--radius-md);
    background: var(--primary-gradient);
    color: #ffffff;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 10px var(--primary-glow);
}

.sidebar-close-btn {
    display: none;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    border: none;
    background: var(--light);
    color: var(--secondary);
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.1rem;
}

.sidebar-body {
    flex: 1;
    overflow-y: auto;
    padding: 16px 12px;
    scrollbar-width: thin;
    scrollbar-color: #cbd5e1 transparent;
}

.sidebar-body::-webkit-scrollbar {
    width: 5px;
}
.sidebar-body::-webkit-scrollbar-thumb {
    background-color: #cbd5e1;
    border-radius: 4px;
}

.sidebar-menu {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.sidebar-menu-category {
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--text-muted);
    letter-spacing: 0.08em;
    padding: 14px 12px 6px;
}

.sidebar-menu li a {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    color: var(--text-dark);
    text-decoration: none;
    border-radius: var(--radius-md);
    font-size: 0.92rem;
    font-weight: 500;
    transition: all 0.2s ease;
}

.sidebar-menu li a i {
    font-size: 1.05rem;
    width: 22px;
    text-align: center;
    color: var(--secondary);
    transition: color 0.2s ease;
}

.sidebar-menu li a:hover {
    background: var(--light);
    color: var(--primary);
}

.sidebar-menu li a:hover i {
    color: var(--primary);
}

.sidebar-menu li a.active {
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 600;
}

.sidebar-menu li a.active i {
    color: var(--primary);
}

.sidebar-footer {
    padding: 14px 16px;
    border-top: 1px solid var(--border-color);
    background: #ffffff;
}

.user-profile-tile {
    display: flex;
    align-items: center;
    gap: 10px;
}

.user-avatar-badge {
    width: 38px;
    height: 38px;
    border-radius: var(--radius-full);
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.9rem;
    border: 2px solid #ffffff;
    box-shadow: var(--shadow-sm);
}

.user-info-text {
    flex: 1;
    min-width: 0;
}

.user-name {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-dark);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.user-role-tag {
    font-size: 0.72rem;
    color: var(--text-muted);
}

/* Sidebar Backdrop for Mobile */
.sidebar-backdrop {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(15, 23, 42, 0.45);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    z-index: 1030;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.sidebar-backdrop.show {
    display: block;
    opacity: 1;
}

/* Cards */
.card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    transition: all 0.25s ease;
    overflow: hidden;
    margin-bottom: 24px;
}

.card:hover {
    box-shadow: var(--shadow-md);
}

.card-header {
    padding: 18px 22px;
    border-bottom: 1px solid var(--border-color);
    background: #ffffff;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
}

.card-header h5, .card-header h4, .card-header h6 {
    margin-bottom: 0;
    font-weight: 700;
}

.card-body {
    padding: 22px;
}

.card-footer {
    padding: 16px 22px;
    background: var(--light);
    border-top: 1px solid var(--border-color);
}

/* Stat Cards */
.stat-card {
    position: relative;
    padding: 22px;
    border-radius: var(--radius-lg);
    background: #ffffff;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    display: flex;
    align-items: center;
    gap: 18px;
    transition: all 0.25s ease;
}

.stat-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    border-color: #cbd5e1;
}

.stat-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    flex-shrink: 0;
}

.stat-icon.primary { background: var(--primary-light); color: var(--primary); }
.stat-icon.success { background: var(--success-light); color: var(--success); }
.stat-icon.warning { background: var(--warning-light); color: var(--warning); }
.stat-icon.danger { background: var(--danger-light); color: var(--danger); }
.stat-icon.info { background: var(--info-light); color: var(--info); }

.stat-content {
    flex: 1;
    min-width: 0;
}

.stat-number {
    font-size: 2rem;
    font-weight: 800;
    color: var(--text-dark);
    line-height: 1.1;
    letter-spacing: -0.02em;
    margin-bottom: 4px;
}

.stat-label {
    color: var(--text-light);
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

/* Buttons */
.btn {
    padding: 10px 20px;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.88rem;
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    line-height: 1.4;
    min-height: 42px;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background: var(--primary);
    color: #ffffff;
    box-shadow: 0 2px 4px var(--primary-glow);
}

.btn-primary:hover {
    background: var(--primary-hover);
    color: #ffffff;
    box-shadow: 0 4px 10px var(--primary-glow);
}

.btn-success {
    background: var(--success);
    color: #ffffff;
    box-shadow: 0 2px 4px rgba(16, 185, 129, 0.25);
}

.btn-success:hover {
    background: var(--success-hover);
    color: #ffffff;
    box-shadow: 0 4px 10px rgba(16, 185, 129, 0.3);
}

.btn-warning {
    background: var(--warning);
    color: #ffffff;
    box-shadow: 0 2px 4px rgba(245, 158, 11, 0.25);
}

.btn-warning:hover {
    background: var(--warning-hover);
    color: #ffffff;
}

.btn-danger {
    background: var(--danger);
    color: #ffffff;
    box-shadow: 0 2px 4px rgba(239, 68, 68, 0.25);
}

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

.btn-secondary {
    background: #ffffff;
    color: var(--text-dark);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--light);
    color: var(--text-dark);
    border-color: #cbd5e1;
}

.btn-light {
    background: var(--light);
    color: var(--text-dark);
    border: 1px solid var(--border-color);
}

.btn-light:hover {
    background: #e2e8f0;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.8rem;
    min-height: 32px;
    border-radius: var(--radius-sm);
}

.btn-lg {
    padding: 14px 28px;
    font-size: 1rem;
    min-height: 50px;
    border-radius: var(--radius-lg);
}

/* Badges */
.badge {
    padding: 5px 10px;
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.02em;
    display: inline-flex;
    align-items: center;
    gap: 5px;
}

.badge-primary, .badge.bg-primary {
    background: var(--primary-light) !important;
    color: var(--primary) !important;
    border: 1px solid rgba(37, 99, 235, 0.15);
}

.badge-success, .badge.bg-success {
    background: var(--success-light) !important;
    color: var(--success) !important;
    border: 1px solid rgba(16, 185, 129, 0.15);
}

.badge-warning, .badge.bg-warning {
    background: var(--warning-light) !important;
    color: #b45309 !important;
    border: 1px solid rgba(245, 158, 11, 0.15);
}

.badge-danger, .badge.bg-danger {
    background: var(--danger-light) !important;
    color: var(--danger) !important;
    border: 1px solid rgba(239, 68, 68, 0.15);
}

.badge-secondary, .badge.bg-secondary {
    background: var(--secondary-light) !important;
    color: var(--secondary) !important;
    border: 1px solid rgba(100, 116, 139, 0.15);
}

.badge-info, .badge.bg-info {
    background: var(--info-light) !important;
    color: #0891b2 !important;
    border: 1px solid rgba(6, 182, 212, 0.15);
}

/* Form Controls */
.form-control, .form-select {
    border-radius: var(--radius-md);
    border: 1.5px solid var(--border-color);
    padding: 10px 14px;
    font-size: 0.92rem;
    color: var(--text-dark);
    background-color: #ffffff;
    transition: all 0.2s ease;
    min-height: 44px;
}

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

.form-label {
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--text-dark);
    margin-bottom: 6px;
}

/* Tables */
.table-responsive {
    border-radius: var(--radius-md);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.table {
    margin-bottom: 0;
    width: 100%;
    vertical-align: middle;
    border-color: var(--border-color);
}

.table th {
    background: var(--light);
    color: var(--text-light);
    font-weight: 700;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    padding: 14px 16px;
    border-bottom: 1.5px solid var(--border-color);
    white-space: nowrap;
}

.table td {
    padding: 14px 16px;
    color: var(--text-main);
    font-size: 0.9rem;
    border-bottom: 1px solid var(--border-color);
}

.table-hover tbody tr:hover {
    background-color: rgba(241, 245, 249, 0.6);
}

/* Alerts */
.alert {
    border-radius: var(--radius-md);
    padding: 14px 18px;
    font-size: 0.9rem;
    border: 1px solid transparent;
    display: flex;
    align-items: center;
    gap: 12px;
}

.alert-success { background: var(--success-light); border-color: rgba(16, 185, 129, 0.2); color: #065f46; }
.alert-warning { background: var(--warning-light); border-color: rgba(245, 158, 11, 0.2); color: #92400e; }
.alert-danger { background: var(--danger-light); border-color: rgba(239, 68, 68, 0.2); color: #991b1b; }
.alert-info { background: var(--info-light); border-color: rgba(6, 182, 212, 0.2); color: #155e75; }

/* Modals */
.modal-content {
    border-radius: var(--radius-xl);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-xl);
    overflow: hidden;
}

.modal-header {
    background: #ffffff;
    padding: 18px 24px;
    border-bottom: 1px solid var(--border-color);
}

.modal-body {
    padding: 24px;
}

.modal-footer {
    background: var(--light);
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
}

/* Responsive Breakpoints & Mobile Optimization */
@media (max-width: 992px) {
    body {
        padding-left: 0 !important;
    }

    .mobile-appbar {
        display: flex;
    }

    .app-sidebar {
        transform: translateX(-100%);
    }

    .app-sidebar.show {
        transform: translateX(0);
    }

    .sidebar-close-btn {
        display: flex;
    }

    .card {
        border-radius: var(--radius-md);
        margin-bottom: 16px;
    }

    .card-body {
        padding: 16px;
    }

    .card-header {
        padding: 14px 16px;
    }

    .stat-card {
        padding: 16px;
        gap: 14px;
    }

    .stat-number {
        font-size: 1.6rem;
    }

    .stat-icon {
        width: 48px;
        height: 48px;
        font-size: 1.25rem;
    }

    .page-header-actions {
        display: flex;
        flex-direction: column;
        gap: 12px;
        margin-bottom: 16px;
    }

    .page-header-actions .btn-group,
    .page-header-actions .btn {
        width: 100%;
    }
}

@media (max-width: 576px) {
    .container {
        padding-left: 12px;
        padding-right: 12px;
    }

    .card-header h5, .card-header h4 {
        font-size: 1.1rem;
    }

    .btn {
        padding: 8px 16px;
        font-size: 0.85rem;
    }
}