/* ============================================================
   NetQuiz - Custom CSS
   Color Palette: Xanh dương (#1a73e8) → Tím (#7c3aed)
   Font: Inter (Google Fonts)
   ============================================================ */

/* === CSS Variables === */
:root {
    --primary: #1a73e8;
    --primary-dark: #1557b0;
    --secondary: #7c3aed;
    --accent: #06b6d4;
    --success: #22c55e;
    --danger: #ef4444;
    --warning: #f59e0b;
    --info: #3b82f6;
    --bg-body: #f0f4f8;
    --bg-card: #ffffff;
    --bg-dark: #0f172a;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06), 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 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
    --shadow-xl: 0 20px 40px -10px rgba(0, 0, 0, 0.12);
    --gradient-primary: linear-gradient(135deg, #1a73e8 0%, #7c3aed 100%);
    --gradient-hero: linear-gradient(135deg, #0f172a 0%, #1e1b4b 50%, #1e3a5f 100%);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* === Reset & Base === */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-body);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.main-content {
    flex: 1;
}

a {
    text-decoration: none;
    transition: var(--transition);
}

/* === Navbar === */
.navbar {
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    padding: 0.75rem 0;
    z-index: 1000;
    transition: var(--transition);
}

.navbar-brand {
    font-weight: 800;
    font-size: 1.4rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.navbar-brand i {
    -webkit-text-fill-color: var(--primary);
}

.nav-link {
    font-weight: 500;
    color: var(--text-secondary) !important;
    padding: 0.5rem 1rem !important;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary) !important;
    background: rgba(26, 115, 232, 0.08);
}

.btn-register-nav {
    background: var(--gradient-primary);
    color: #fff !important;
    -webkit-text-fill-color: unset;
    border-radius: 50px !important;
    padding: 0.5rem 1.25rem !important;
    font-weight: 600;
}

.btn-register-nav:hover {
    opacity: 0.9;
    color: #fff !important;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(26, 115, 232, 0.3);
}

/* === Gradient Text === */
.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* === Hero Section === */
.hero-section {
    background: var(--gradient-hero);
    color: #fff;
    padding: 5rem 0 4rem;
    position: relative;
    overflow: hidden;
}

.hero-section::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(124, 58, 237, 0.15) 0%, transparent 70%);
    border-radius: 50%;
}

.hero-section::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -10%;
    width: 400px;
    height: 400px;
    background: radial-gradient(circle, rgba(26, 115, 232, 0.12) 0%, transparent 70%);
    border-radius: 50%;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1.5rem;
}

.hero-title .gradient-text {
    background: linear-gradient(135deg, #60a5fa, #a78bfa, #c084fc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: rgba(255, 255, 255, 0.75);
    max-width: 550px;
    margin-bottom: 2rem;
    line-height: 1.7;
}

.hero-stats {
    display: flex;
    gap: 2rem;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.1);
    padding: 0.6rem 1.2rem;
    border-radius: 50px;
    backdrop-filter: blur(10px);
}

.stat-item i {
    color: var(--accent);
    font-size: 1.1rem;
}

.stat-number {
    font-weight: 700;
    font-size: 1.1rem;
}

.stat-label {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.85rem;
}

/* Floating cards animation */
.hero-visual {
    position: relative;
    height: 350px;
}

.floating-card {
    position: absolute;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.15);
    padding: 0.8rem 1.5rem;
    border-radius: var(--radius-md);
    backdrop-filter: blur(10px);
    font-weight: 600;
    font-size: 0.95rem;
    animation: float 6s ease-in-out infinite;
    white-space: nowrap;
}

.floating-card i {
    margin-right: 0.4rem;
}

.card-1 { top: 10%; left: 15%; animation-delay: 0s; }
.card-2 { top: 35%; right: 10%; animation-delay: 1.5s; }
.card-3 { bottom: 25%; left: 5%; animation-delay: 3s; }
.card-4 { bottom: 10%; right: 20%; animation-delay: 4.5s; font-size: 1.2rem; }

@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-15px); }
}

/* === Section Styles === */
.topics-section {
    padding: 4rem 0;
}

.how-section {
    padding: 4rem 0;
    background: var(--bg-card);
}

.section-header {
    margin-bottom: 3rem;
}

.section-header h2 {
    font-weight: 700;
    font-size: 1.8rem;
    margin-bottom: 0.5rem;
}

.section-header h2 i {
    color: var(--primary);
}

/* === Topic Cards === */
.topic-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 2rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    height: 100%;
    display: flex;
    flex-direction: column;
    position: relative;
    overflow: hidden;
}

.topic-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: var(--transition);
}

.topic-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-xl);
    border-color: rgba(26, 115, 232, 0.2);
}

.topic-card:hover::before {
    opacity: 1;
}

.topic-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius-md);
    background: linear-gradient(135deg, rgba(26, 115, 232, 0.1) 0%, rgba(124, 58, 237, 0.1) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.25rem;
}

.topic-icon i {
    font-size: 1.5rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.topic-name {
    font-weight: 700;
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.topic-desc {
    color: var(--text-secondary);
    font-size: 0.9rem;
    flex: 1;
    margin-bottom: 1rem;
    line-height: 1.6;
}

.topic-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.25rem;
    font-size: 0.82rem;
    color: var(--text-muted);
}

.topic-meta i {
    color: var(--primary);
    margin-right: 0.2rem;
}

.topic-actions {
    display: flex;
    gap: 0.75rem;
}

.topic-actions .btn {
    flex: 1;
    font-weight: 600;
    font-size: 0.85rem;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
}

/* === Step Cards === */
.step-card {
    text-align: center;
    padding: 2rem;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    transition: var(--transition);
    background: var(--bg-body);
}

.step-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.step-number {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--gradient-primary);
    color: #fff;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-weight: 800;
    font-size: 1.2rem;
    margin-bottom: 1rem;
}

.step-card h4 {
    font-weight: 700;
    font-size: 1.1rem;
    margin-bottom: 0.75rem;
}

.step-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0;
}

/* === Lesson Page === */
.lesson-section {
    padding: 2rem 0 4rem;
}

.lesson-sidebar {
    position: sticky;
    top: 90px;
    background: var(--bg-card);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

.lesson-sidebar h5 {
    font-weight: 700;
    font-size: 1rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.lesson-toc {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.toc-link {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 500;
    border-left: 3px solid transparent;
    transition: var(--transition);
}

.toc-link:hover, .toc-link.active {
    color: var(--primary);
    background: rgba(26, 115, 232, 0.06);
    border-left-color: var(--primary);
}

.toc-number {
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--bg-body);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 700;
    flex-shrink: 0;
}

.toc-link.active .toc-number {
    background: var(--primary);
    color: #fff;
}

.lesson-header {
    margin-bottom: 2rem;
}

.lesson-topic-badge {
    display: inline-block;
    padding: 0.35rem 1rem;
    border-radius: 50px;
    background: linear-gradient(135deg, rgba(26, 115, 232, 0.1), rgba(124, 58, 237, 0.1));
    color: var(--primary);
    font-size: 0.82rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.lesson-header h1 {
    font-weight: 800;
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.lesson-content-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

.lesson-content h2 {
    font-weight: 700;
    font-size: 1.5rem;
    margin: 1.5rem 0 1rem;
    color: var(--text-primary);
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
}

.lesson-content h2:first-child {
    margin-top: 0;
}

.lesson-content h3 {
    font-weight: 600;
    font-size: 1.2rem;
    margin: 1.5rem 0 0.75rem;
    color: var(--primary-dark);
}

.lesson-content h4 {
    font-weight: 600;
    font-size: 1.05rem;
    margin: 1rem 0 0.5rem;
}

.lesson-content p {
    margin-bottom: 0.75rem;
}

.lesson-content code {
    background: rgba(26, 115, 232, 0.08);
    color: var(--primary-dark);
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
    font-size: 0.9em;
}

.lesson-content .table {
    font-size: 0.9rem;
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin: 1rem 0;
}

.lesson-content .alert {
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
}

.lesson-cta {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    border: 2px dashed var(--border-color);
    margin-top: 1rem;
}

/* === Quiz Page === */
.quiz-section {
    padding: 2rem 0 4rem;
}

.quiz-header {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 2rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

.quiz-progress-bar {
    height: 8px;
    border-radius: 4px;
    background: var(--bg-body);
    overflow: hidden;
    margin-top: 1rem;
}

.quiz-progress-fill {
    height: 100%;
    border-radius: 4px;
    background: var(--gradient-primary);
    transition: width 0.5s ease;
    width: 0%;
}

.quiz-progress-text {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
}

.question-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 2rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    margin-bottom: 1.5rem;
    transition: var(--transition);
}

.question-card.answered {
    border-color: rgba(26, 115, 232, 0.3);
}

.question-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    min-width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--gradient-primary);
    color: #fff;
    font-weight: 700;
    font-size: 0.85rem;
    margin-right: 0.75rem;
    flex-shrink: 0;
}

.question-text {
    font-weight: 600;
    font-size: 1.05rem;
    margin-bottom: 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.question-text .question-content {
    flex: 1;
}

.difficulty-badge {
    font-size: 0.7rem;
    padding: 0.2rem 0.6rem;
    border-radius: 50px;
    font-weight: 600;
    margin-left: 0.75rem;
    white-space: nowrap;
}

.difficulty-easy {
    background: rgba(34, 197, 94, 0.1);
    color: var(--success);
}

.difficulty-medium {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning);
}

.difficulty-hard {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

.answer-option {
    display: block;
    padding: 0.85rem 1.25rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    margin-bottom: 0.5rem;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.95rem;
}

.answer-option:hover {
    border-color: var(--primary);
    background: rgba(26, 115, 232, 0.04);
}

.answer-option input[type="radio"] {
    margin-right: 0.75rem;
    accent-color: var(--primary);
    transform: scale(1.2);
}

.answer-option:has(input:checked) {
    border-color: var(--primary);
    background: rgba(26, 115, 232, 0.06);
    box-shadow: 0 0 0 1px var(--primary);
}

.quiz-submit-area {
    text-align: center;
    padding: 2rem;
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.quiz-submit-area .btn-primary {
    padding: 0.75rem 3rem;
    font-size: 1.1rem;
    font-weight: 700;
    border-radius: 50px;
}

/* === Result Page === */
.result-section {
    padding: 2rem 0 4rem;
}

.result-score-card {
    background: var(--bg-card);
    border-radius: var(--radius-xl);
    padding: 3rem;
    text-align: center;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
    margin-bottom: 2rem;
}

.score-circle {
    width: 160px;
    height: 160px;
    border-radius: 50%;
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.5rem;
    position: relative;
}

.score-circle.excellent {
    background: linear-gradient(135deg, rgba(34, 197, 94, 0.1), rgba(34, 197, 94, 0.05));
    border: 4px solid var(--success);
}

.score-circle.good {
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.1), rgba(59, 130, 246, 0.05));
    border: 4px solid var(--info);
}

.score-circle.average {
    background: linear-gradient(135deg, rgba(245, 158, 11, 0.1), rgba(245, 158, 11, 0.05));
    border: 4px solid var(--warning);
}

.score-circle.poor {
    background: linear-gradient(135deg, rgba(239, 68, 68, 0.1), rgba(239, 68, 68, 0.05));
    border: 4px solid var(--danger);
}

.score-number {
    font-size: 2.5rem;
    font-weight: 800;
    line-height: 1;
}

.score-total {
    font-size: 1rem;
    color: var(--text-muted);
    font-weight: 500;
}

.score-percentage {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 0.25rem;
}

.score-message {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

.result-detail-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 1.75rem;
    border: 1px solid var(--border-color);
    margin-bottom: 1.25rem;
    box-shadow: var(--shadow-sm);
}

.result-detail-card.correct {
    border-left: 4px solid var(--success);
}

.result-detail-card.incorrect {
    border-left: 4px solid var(--danger);
}

.result-detail-card.skipped {
    border-left: 4px solid var(--text-muted);
}

.result-status {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.25rem 0.75rem;
    border-radius: 50px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.result-status.correct {
    background: rgba(34, 197, 94, 0.1);
    color: var(--success);
}

.result-status.incorrect {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
}

.result-status.skipped {
    background: rgba(148, 163, 184, 0.15);
    color: var(--text-muted);
}

.answer-result {
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-sm);
    margin-bottom: 0.25rem;
    font-size: 0.9rem;
}

.answer-correct {
    background: rgba(34, 197, 94, 0.1);
    border: 1px solid rgba(34, 197, 94, 0.3);
    color: #166534;
}

.answer-wrong {
    background: rgba(239, 68, 68, 0.1);
    border: 1px solid rgba(239, 68, 68, 0.3);
    color: #991b1b;
}

.explanation-box {
    background: rgba(245, 158, 11, 0.06);
    border: 1px solid rgba(245, 158, 11, 0.2);
    border-radius: var(--radius-sm);
    padding: 0.75rem 1rem;
    margin-top: 0.75rem;
    font-size: 0.88rem;
    color: #92400e;
}

.explanation-box i {
    color: var(--warning);
}

.result-actions {
    text-align: center;
    margin-top: 2rem;
}

.result-actions .btn {
    padding: 0.65rem 2rem;
    font-weight: 600;
    border-radius: 50px;
    margin: 0 0.5rem;
}

/* === Auth Pages === */
.auth-section {
    padding: 3rem 0;
    min-height: calc(100vh - 200px);
    display: flex;
    align-items: center;
}

.auth-card {
    background: var(--bg-card);
    border-radius: var(--radius-xl);
    padding: 2.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
    max-width: 450px;
    margin: 0 auto;
}

.auth-card h2 {
    font-weight: 800;
    text-align: center;
    margin-bottom: 0.25rem;
}

.auth-card .auth-subtitle {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: 2rem;
    font-size: 0.9rem;
}

.auth-card .form-label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-primary);
}

.auth-card .form-control {
    border-radius: var(--radius-sm);
    border: 2px solid var(--border-color);
    padding: 0.65rem 1rem;
    font-size: 0.95rem;
    transition: var(--transition);
}

.auth-card .form-control:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(26, 115, 232, 0.1);
}

.auth-card .btn-primary {
    width: 100%;
    padding: 0.7rem;
    font-weight: 700;
    font-size: 1rem;
    border-radius: var(--radius-sm);
    margin-top: 0.5rem;
}

.auth-footer {
    text-align: center;
    margin-top: 1.5rem;
    font-size: 0.9rem;
    color: var(--text-muted);
}

.auth-footer a {
    color: var(--primary);
    font-weight: 600;
}

/* === History Page === */
.history-section {
    padding: 2rem 0 4rem;
}

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

.history-table .table {
    margin: 0;
}

.history-table .table th {
    background: var(--bg-body);
    font-weight: 700;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
    border-bottom: 2px solid var(--border-color);
    padding: 0.85rem 1.25rem;
}

.history-table .table td {
    padding: 0.85rem 1.25rem;
    vertical-align: middle;
    font-size: 0.9rem;
}

.score-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.3rem 0.75rem;
    border-radius: 50px;
    font-weight: 700;
    font-size: 0.82rem;
}

.score-badge.excellent { background: rgba(34, 197, 94, 0.1); color: var(--success); }
.score-badge.good { background: rgba(59, 130, 246, 0.1); color: var(--info); }
.score-badge.average { background: rgba(245, 158, 11, 0.1); color: var(--warning); }
.score-badge.poor { background: rgba(239, 68, 68, 0.1); color: var(--danger); }

.chart-container {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    margin-bottom: 2rem;
}

/* === Admin === */
.admin-section {
    padding: 2rem 0 4rem;
}

.admin-stat-card {
    background: var(--bg-card);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    text-align: center;
    transition: var(--transition);
}

.admin-stat-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.admin-stat-card .stat-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    margin-bottom: 0.75rem;
}

.admin-stat-card .stat-value {
    font-size: 1.8rem;
    font-weight: 800;
    color: var(--text-primary);
}

.admin-stat-card .stat-label {
    font-size: 0.82rem;
    color: var(--text-muted);
    font-weight: 500;
}

.admin-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

.admin-card h5 {
    font-weight: 700;
    margin-bottom: 1rem;
}

/* === Buttons Overrides === */
.btn-primary {
    background: var(--gradient-primary);
    border: none;
    font-weight: 600;
    transition: var(--transition);
}

.btn-primary:hover {
    opacity: 0.92;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(26, 115, 232, 0.3);
}

.btn-outline-primary {
    border: 2px solid var(--primary);
    color: var(--primary);
    font-weight: 600;
}

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

/* === Footer === */
.footer {
    background: var(--bg-dark);
    color: rgba(255, 255, 255, 0.8);
    padding: 1.5rem 0;
    margin-top: auto;
}

.footer p {
    font-size: 0.88rem;
}

/* === Breadcrumb === */
.breadcrumb {
    font-size: 0.88rem;
    background: none;
    padding: 0;
}

.breadcrumb-item a {
    color: var(--primary);
    font-weight: 500;
}

.breadcrumb-item.active {
    color: var(--text-muted);
}

/* === Responsive === */
@media (max-width: 768px) {
    .hero-title {
        font-size: 2rem;
    }

    .hero-stats {
        flex-wrap: wrap;
        gap: 0.75rem;
    }

    .stat-item {
        padding: 0.4rem 0.8rem;
        font-size: 0.85rem;
    }

    .lesson-content-card {
        padding: 1.5rem;
    }

    .question-card {
        padding: 1.25rem;
    }

    .result-score-card {
        padding: 2rem 1.5rem;
    }

    .score-circle {
        width: 120px;
        height: 120px;
    }

    .score-number {
        font-size: 2rem;
    }

    .result-actions .btn {
        display: block;
        width: 100%;
        margin: 0.5rem 0;
    }

    .auth-card {
        padding: 1.5rem;
        margin: 0 1rem;
    }
}

@media (max-width: 576px) {
    .topic-actions {
        flex-direction: column;
    }

    .topic-actions .btn {
        width: 100%;
    }
}

/* === Animation Utilities === */
.fade-in {
    animation: fadeIn 0.5s ease forwards;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.slide-up {
    animation: slideUp 0.4s ease forwards;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

/* === Empty State === */
.empty-state {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--text-muted);
}

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.empty-state h4 {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}