:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #10b981;
    --secondary-dark: #059669;
    --accent-color: #f59e0b;
    --danger-color: #ef4444;
    --success-color: #22c55e;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    --bg-color: #f8fafc;
    --bg-dark: #1e293b;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    --radius-sm: 0.375rem;
    --radius: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --transition: all 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.logo i {
    font-size: 1.8rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 40px;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    padding: 8px 16px;
    border-radius: var(--radius);
    transition: var(--transition);
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.nav-user {
    display: flex;
    align-items: center;
    gap: 12px;
}

.user-name {
    color: var(--text-secondary);
    font-weight: 500;
}

.user-avatar {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    cursor: pointer;
}

.page-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 120px 20px 60px;
    text-align: center;
}

.page-header h1 {
    font-size: 2.5rem;
    color: white;
    margin-bottom: 15px;
}

.page-header p {
    color: rgba(255, 255, 255, 0.9);
    font-size: 1.1rem;
}

.main-content {
    padding: 60px 0;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 14px 28px;
    border-radius: var(--radius-lg);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

.btn-secondary {
    background: var(--bg-color);
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
}

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

.footer {
    background: var(--bg-dark);
    color: white;
    padding: 40px 0 30px;
    margin-top: 80px;
}

.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding-top: 30px;
    text-align: center;
    color: var(--text-light);
}

.upload-section,
.practice-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
}

.upload-box,
.preview-section,
.result-card,
.practice-main,
.sidebar {
    background: white;
    border-radius: var(--radius-xl);
    padding: 40px;
    box-shadow: var(--shadow);
}

.upload-area {
    border: 3px dashed var(--border-color);
    border-radius: var(--radius-xl);
    padding: 60px 40px;
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    margin-bottom: 30px;
}

.upload-area:hover,
.upload-area.dragover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.05);
}

.upload-area i {
    font-size: 4rem;
    color: var(--primary-color);
    margin-bottom: 20px;
}

.option-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 20px;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

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

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

.text-input-area {
    display: none;
}

.text-input-area.show {
    display: block;
}

.text-input-area textarea {
    width: 100%;
    min-height: 200px;
    padding: 20px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    font-size: 1rem;
    font-family: inherit;
    resize: vertical;
}

.text-input-area textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.95);
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

.loading-overlay.show {
    display: flex;
}

.loading-spinner {
    width: 60px;
    height: 60px;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.progress-bar {
    height: 8px;
    background: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--primary-light));
    border-radius: 4px;
    transition: width 0.3s ease;
}

.practice-section {
    grid-template-columns: 300px 1fr;
}

.sidebar {
    height: fit-content;
    position: sticky;
    top: 90px;
}

.knowledge-list {
    list-style: none;
}

.knowledge-list li {
    padding: 10px 15px;
    margin-bottom: 8px;
    background: var(--bg-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.knowledge-list li:hover,
.knowledge-list li.active {
    background: var(--primary-color);
    color: white;
}

.question-card {
    background: var(--bg-color);
    border-radius: var(--radius-lg);
    padding: 30px;
    margin-bottom: 25px;
}

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

.answer-option {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 15px 20px;
    background: white;
    border: 2px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
}

.answer-option:hover {
    border-color: var(--primary-color);
}

.answer-option.selected {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.answer-option.correct {
    border-color: var(--success-color);
    background: rgba(34, 197, 94, 0.1);
}

.answer-option.wrong {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.1);
}

.report-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 30px;
}

.report-card {
    background: white;
    border-radius: var(--radius-xl);
    padding: 30px;
    box-shadow: var(--shadow);
}

.report-card.full-width {
    grid-column: span 2;
}

@media (max-width: 1024px) {
    .upload-section,
    .practice-section,
    .report-section {
        grid-template-columns: 1fr;
    }
    .sidebar {
        position: static;
    }
    .report-card.full-width {
        grid-column: span 1;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
}