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

:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary: #64748b;
    --danger: #ef4444;
    --success: #22c55e;
    --warning: #f59e0b;
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 25px rgba(0,0,0,0.1);
    --radius: 8px;
    --radius-lg: 12px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

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

/* Header */
.header {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    padding: 0 24px;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

.header h1 {
    font-size: 1.25rem;
    font-weight: 600;
    padding: 16px 0;
    color: var(--text);
}

.nav-tabs {
    display: flex;
    gap: 4px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
    overflow-x: auto;
}

.nav-tab {
    padding: 10px 20px;
    border: none;
    background: transparent;
    color: var(--text-muted);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius);
    white-space: nowrap;
    transition: all 0.2s;
}

.nav-tab:hover {
    background: var(--bg);
    color: var(--text);
}

.nav-tab.active {
    background: var(--primary);
    color: white;
}

/* Main Content */
.main-content {
    flex: 1;
    padding: 24px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

/* Page Header */
.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    flex-wrap: wrap;
    gap: 16px;
}

.page-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
}

/* Buttons */
.btn {
    padding: 10px 20px;
    border: none;
    border-radius: var(--radius);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary {
    background: var(--primary);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background: var(--primary-hover);
}

.btn-secondary {
    background: var(--secondary);
    color: white;
}

.btn-secondary:hover:not(:disabled) {
    background: #475569;
}

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

.btn-danger:hover:not(:disabled) {
    background: #dc2626;
}

.btn-success {
    background: var(--success);
    color: white;
}

.btn-block {
    width: 100%;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.stat-card {
    background: var(--card-bg);
    padding: 20px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 16px;
}

.stat-icon {
    font-size: 2.5rem;
}

.stat-info h3 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary);
}

.stat-info p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Quick Actions */
.quick-actions {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

/* Recent Tests */
.recent-tests h3 {
    font-size: 1.1rem;
    margin-bottom: 12px;
}

.recent-test-item {
    background: var(--card-bg);
    padding: 16px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 8px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.recent-test-info {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.recent-test-meta {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.recent-test-score {
    font-weight: 600;
    font-size: 1.1rem;
}

.recent-test-score.excellent { color: var(--success); }
.recent-test-score.good { color: var(--primary); }
.recent-test-score.poor { color: var(--danger); }

/* Filter Bar */
.filter-bar {
    display: flex;
    gap: 12px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.filter-bar select,
.filter-bar input {
    padding: 10px 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 0.9rem;
    background: var(--card-bg);
}

.filter-bar input {
    flex: 1;
    min-width: 200px;
}

/* Question List */
.question-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.question-item {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 20px;
    transition: box-shadow 0.2s;
}

.question-item:hover {
    box-shadow: var(--shadow-lg);
}

.question-item-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 12px;
    gap: 12px;
}

.question-meta {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

.question-category {
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    background: #dbeafe;
    color: var(--primary);
}

.question-category.hse {
    background: #fef3c7;
    color: var(--warning);
}

.question-type {
    font-size: 0.75rem;
    color: var(--text-muted);
    background: var(--bg);
    padding: 4px 12px;
    border-radius: 20px;
}

.question-score {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.question-text {
    font-size: 1rem;
    font-weight: 500;
    margin-bottom: 12px;
    line-height: 1.7;
}

.question-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 8px;
    margin-bottom: 12px;
}

.question-option {
    padding: 8px 12px;
    background: var(--bg);
    border-radius: var(--radius);
    font-size: 0.9rem;
}

.question-option.correct {
    background: #dcfce7;
    color: var(--success);
    font-weight: 500;
}

.question-actions {
    display: flex;
    gap: 8px;
}

.question-actions .btn {
    padding: 6px 12px;
    font-size: 0.8rem;
}

/* Study Mode */
.study-controls {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

.study-controls select {
    padding: 10px 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 0.9rem;
    background: var(--card-bg);
}

.study-progress-bar {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 24px;
    background: var(--card-bg);
    padding: 16px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.progress-fill {
    flex: 1;
    height: 8px;
    background: var(--bg);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill::after {
    content: '';
    display: block;
    width: 0%;
    height: 100%;
    background: var(--primary);
    transition: width 0.3s ease;
}

.study-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 32px;
    min-height: 300px;
}

.study-card .empty-state {
    text-align: center;
    color: var(--text-muted);
    padding: 60px 0;
}

.study-question {
    animation: slideIn 0.3s ease;
}

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

.study-question .question-text {
    font-size: 1.25rem;
    margin-bottom: 24px;
}

.study-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 24px;
}

.study-option {
    padding: 16px 20px;
    background: var(--bg);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.2s;
    border: 2px solid transparent;
    display: flex;
    align-items: center;
    gap: 12px;
}

.study-option:hover {
    background: #e2e8f0;
}

.study-option.selected {
    border-color: var(--primary);
    background: #dbeafe;
}

.study-option.correct {
    border-color: var(--success);
    background: #dcfce7;
}

.study-option.incorrect {
    border-color: var(--danger);
    background: #fee2e2;
}

.study-option-letter {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--primary);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.study-option.correct .study-option-letter {
    background: var(--success);
}

.study-option.incorrect .study-option-letter {
    background: var(--danger);
}

.study-explanation {
    padding: 16px;
    background: #fef3c7;
    border-radius: var(--radius);
    border-left: 4px solid var(--warning);
}

.study-nav {
    display: flex;
    justify-content: space-between;
    margin-top: 24px;
    padding-top: 24px;
    border-top: 1px solid var(--border);
}

/* Test Mode */
.test-setup {
    max-width: 600px;
    margin: 0 auto;
}

.setup-card {
    background: var(--card-bg);
    padding: 32px;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
}

.setup-card h3 {
    margin-bottom: 24px;
    font-size: 1.25rem;
}

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

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 10px 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 0.95rem;
}

.radio-group {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.radio-group label {
    display: flex;
    align-items: center;
    gap: 12px;
    cursor: pointer;
    padding: 12px 16px;
    background: var(--bg);
    border-radius: var(--radius);
    transition: all 0.2s;
}

.radio-group label:hover {
    background: #e2e8f0;
}

.radio-group input[type="radio"] {
    width: 18px;
    height: 18px;
    accent-color: var(--primary);
}

.test-running.hidden,
.test-result.hidden {
    display: none;
}

.test-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    padding: 16px;
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.test-progress {
    display: flex;
    flex-direction: column;
    gap: 8px;
    min-width: 200px;
}

.test-progress span {
    font-weight: 600;
    font-size: 1.1rem;
}

.test-timer {
    font-size: 1.5rem;
    font-weight: 700;
    font-family: monospace;
    color: var(--primary);
    background: var(--bg);
    padding: 8px 16px;
    border-radius: var(--radius);
}

.test-question {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 32px;
    margin-bottom: 24px;
    animation: slideIn 0.3s ease;
}

.test-question .question-text {
    font-size: 1.25rem;
    margin-bottom: 24px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

.test-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.test-option {
    padding: 16px 20px;
    background: var(--bg);
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.2s;
    border: 2px solid transparent;
    display: flex;
    align-items: center;
    gap: 12px;
}

.test-option:hover {
    background: #e2e8f0;
}

.test-option.selected {
    border-color: var(--primary);
    background: #dbeafe;
}

.test-option-letter {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--border);
    color: var(--text);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
    transition: all 0.2s;
}

.test-option.selected .test-option-letter {
    background: var(--primary);
    color: white;
}

.test-nav {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    padding-top: 16px;
    border-top: 1px solid var(--border);
}

/* Test Result */
.test-result {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 32px;
    text-align: center;
}

.test-result h3 {
    margin-bottom: 24px;
    font-size: 1.5rem;
}

.result-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 16px;
    margin-bottom: 32px;
}

.result-item {
    padding: 20px;
    background: var(--bg);
    border-radius: var(--radius);
}

.result-item .label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.result-item .value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary);
}

.result-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

/* Wrong Bank */
.wrong-bank-actions {
    display: flex;
    gap: 12px;
}

.wrong-bank-stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
    padding: 16px;
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.wrong-bank-categories {
    display: flex;
    gap: 8px;
}

.wrong-category-tag {
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    background: #fee2e2;
    color: var(--danger);
}

/* Modals */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 24px;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 600px;
    max-height: 90vh;
    overflow-y: auto;
    transform: scale(0.9);
    transition: transform 0.3s;
}

.modal-overlay.active .modal {
    transform: scale(1);
}

.modal-lg {
    max-width: 800px;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
}

.modal-header h3 {
    font-size: 1.25rem;
    font-weight: 600;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
    padding: 4px;
    line-height: 1;
}

.modal-close:hover {
    color: var(--text);
}

#question-form {
    padding: 24px;
}

.options-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 12px;
    margin-top: 24px;
    padding-top: 16px;
    border-top: 1px solid var(--border);
}

/* Question Detail Modal */
.question-detail {
    padding: 24px;
}

.question-detail-header {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 16px;
}

.question-detail-text {
    font-size: 1.1rem;
    font-weight: 500;
    margin-bottom: 20px;
    line-height: 1.7;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

.question-detail-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 20px;
}

.question-detail-option {
    padding: 12px 16px;
    background: var(--bg);
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    gap: 12px;
}

.question-detail-option.correct {
    background: #dcfce7;
    color: var(--success);
    font-weight: 500;
}

.question-detail-option-letter {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--border);
    color: var(--text);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    flex-shrink: 0;
}

.question-detail-option.correct .question-detail-option-letter {
    background: var(--success);
    color: white;
}

.question-detail-meta {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    font-size: 0.85rem;
    color: var(--text-muted);
    padding-top: 16px;
    border-top: 1px solid var(--border);
}

/* Responsive */
@media (max-width: 768px) {
    .header {
        padding: 0 16px;
    }
    
    .main-content {
        padding: 16px;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .question-options {
        grid-template-columns: 1fr;
    }
    
    .options-grid {
        grid-template-columns: 1fr;
    }
    
    .test-header {
        flex-direction: column;
        gap: 12px;
        align-items: stretch;
    }
    
    .result-summary {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .wrong-bank-stats {
        flex-direction: column;
        gap: 12px;
        align-items: flex-start;
    }
}