/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
    overflow-x: hidden;
    overflow-y: auto;
}

/* 屏幕管理 */
.screen {
    min-height: 100vh;
    padding: 20px;
    transition: all 0.3s ease;
    overflow-y: auto;
}

.hidden {
    display: none !important;
}

/* 加载页面 */
#loading-screen {
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.loading-container {
    text-align: center;
    color: white;
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top: 4px solid white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* 主页面样式 */
.app-header {
    text-align: center;
    margin-bottom: 30px;
    color: white;
}

.app-header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* 统计卡片 */
.stats-container {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    margin-bottom: 25px;
}

.stat-card {
    background: rgba(255, 255, 255, 0.95);
    padding: 15px 10px;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 16px rgba(0,0,0,0.1);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.stat-number {
    font-size: 1.5rem;
    font-weight: bold;
    color: #4CAF50;
    margin-bottom: 3px;
}

.stat-label {
    font-size: 0.8rem;
    color: #666;
}

/* 学习计划 */
.study-plan {
    background: rgba(255, 255, 255, 0.95);
    padding: 20px;
    border-radius: 15px;
    margin-bottom: 25px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.1);
}

.study-plan h3 {
    margin-bottom: 15px;
    color: #333;
    font-size: 1.2rem;
}

.plan-days {
    display: grid;
    gap: 10px;
}

.plan-day {
    padding: 12px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    transition: all 0.3s ease;
    cursor: pointer;
}

.plan-day:hover {
    border-color: #4CAF50;
    transform: translateY(-2px);
}

.plan-day.active {
    border-color: #4CAF50;
    background: #f8fff8;
}

.plan-day.completed {
    border-color: #2e7d32;
    background: #e8f5e8;
}

.plan-day.completed .day-header {
    color: #2e7d32;
}

.estimated-time {
    font-size: 0.75rem;
    color: #666;
    margin-top: 3px;
    font-style: italic;
}

.day-header {
    font-weight: bold;
    margin-bottom: 6px;
    color: #333;
    font-size: 0.95rem;
}

.day-progress {
    display: flex;
    align-items: center;
    gap: 8px;
}

.progress-bar {
    flex: 1;
    height: 6px;
    background: #e0e0e0;
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #4CAF50, #45a049);
    border-radius: 3px;
    transition: width 0.3s ease;
    width: 0%;
}

.progress-text {
    font-size: 0.8rem;
    color: #666;
    min-width: 45px;
}

/* 按钮样式 */
.action-buttons {
    display: grid;
    gap: 15px;
}

.btn {
    padding: 15px 25px;
    border: none;
    border-radius: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background: linear-gradient(135deg, #4CAF50, #45a049);
    color: white;
    box-shadow: 0 4px 15px rgba(76, 175, 80, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(76, 175, 80, 0.4);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.95);
    color: #333;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0,0,0,0.15);
}

.btn-outline {
    background: transparent;
    color: #4CAF50;
    border: 2px solid #4CAF50;
}

.btn-outline:hover {
    background: #4CAF50;
    color: white;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

/* 答题页面样式 */
.quiz-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
    background: rgba(255, 255, 255, 0.95);
    padding: 12px 16px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    position: relative;
}

.btn-back {
    background: none;
    border: none;
    font-size: 1rem;
    color: #4CAF50;
    cursor: pointer;
    padding: 6px 10px;
    border-radius: 6px;
    transition: background 0.3s ease;
    display: flex;
    align-items: center;
    gap: 5px;
}

.btn-back:hover {
    background: rgba(76, 175, 80, 0.1);
}

.quiz-progress {
    font-weight: 600;
    color: #333;
    font-size: 1rem;
    background: #f0f8f0;
    padding: 6px 12px;
    border-radius: 12px;
    border: 1px solid #e0f0e0;
    min-width: 70px;
    text-align: center;
}

.quiz-timer {
    font-family: 'Courier New', monospace;
    font-weight: 600;
    color: #666;
    font-size: 0.95rem;
    background: #f8f9fa;
    padding: 6px 12px;
    border-radius: 12px;
    border: 1px solid #e9ecef;
    min-width: 60px;
    text-align: center;
}

/* 题目容器 */
.question-container {
    background: rgba(255, 255, 255, 0.95);
    padding: 24px;
    border-radius: 12px;
    margin-bottom: 20px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.1);
}

.question-number {
    font-size: 1.1rem;
    color: #4CAF50;
    font-weight: bold;
    margin-bottom: 15px;
}

.question-text {
    font-size: 1.2rem;
    line-height: 1.5;
    color: #333;
}

/* 选项容器 */
.options-container {
    display: grid;
    gap: 12px;
    margin-bottom: 25px;
}

.option {
    background: rgba(255, 255, 255, 0.95);
    padding: 18px 20px;
    border-radius: 10px;
    border: 2px solid #e0e0e0;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 12px;
}

.option:hover {
    border-color: #4CAF50;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.option.selected {
    border-color: #4CAF50;
    background: #f8fff8;
}

.option.correct {
    border-color: #4CAF50;
    background: #e8f5e8;
}

.option.incorrect {
    border-color: #f44336;
    background: #ffebee;
}

.option-label {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: #e0e0e0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    color: white;
    flex-shrink: 0;
    font-size: 1rem;
}

.option.selected .option-label {
    background: #4CAF50;
}

.option-text {
    flex: 1;
    font-size: 1.1rem;
    line-height: 1.4;
}

/* 题目操作按钮 */
.question-actions {
    display: flex;
    gap: 15px;
    justify-content: space-between;
    margin-top: 15px;
}



/* 反馈弹窗 */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal-content {
    background: white;
    padding: 30px;
    border-radius: 15px;
    text-align: center;
    max-width: 400px;
    width: 90%;
    box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}

.feedback-icon {
    font-size: 3rem;
    margin-bottom: 15px;
}

.feedback-icon.correct {
    color: #4CAF50;
}

.feedback-icon.incorrect {
    color: #f44336;
}

.feedback-text {
    font-size: 1.3rem;
    font-weight: bold;
    margin-bottom: 10px;
}

.correct-answer-text {
    color: #666;
    font-size: 1rem;
}

/* 页面头部 */
.page-header {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-bottom: 25px;
    color: white;
}

.page-header h2 {
    margin: 0;
}

/* 知识点分类样式 */
.knowledge-categories {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.knowledge-category {
    background: rgba(255, 255, 255, 0.95);
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.1);
    transition: transform 0.3s ease;
}

.knowledge-category:hover {
    transform: translateY(-5px);
}

.category-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 15px;
}

.knowledge-category h3 {
    color: #333;
    margin: 0;
    font-size: 1.3rem;
}

.category-description {
    color: #666;
    margin-bottom: 15px;
    line-height: 1.5;
    font-size: 0.95rem;
}

.category-stats {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
    padding: 10px;
    background: #f8f9fa;
    border-radius: 8px;
}

.stat-item {
    text-align: center;
}

.stat-label {
    display: block;
    font-size: 0.8rem;
    color: #888;
    margin-bottom: 2px;
}

.stat-value {
    display: block;
    font-size: 1.1rem;
    font-weight: bold;
    color: #333;
}

.difficulty-distribution {
    display: flex;
    gap: 8px;
    margin-bottom: 15px;
    flex-wrap: wrap;
}

.category-progress {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
}

/* 统计页面样式 */
.stats-content {
    background: rgba(255, 255, 255, 0.95);
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.1);
}

.stats-overview {
    margin-bottom: 30px;
}

.stats-overview h3 {
    color: #333;
    margin-bottom: 20px;
    font-size: 1.4rem;
}

.overview-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 15px;
    margin-bottom: 20px;
}

.overview-card {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    border-left: 4px solid #4CAF50;
}

.overview-number {
    font-size: 2.2rem;
    font-weight: bold;
    color: #4CAF50;
    margin-bottom: 5px;
}

.overview-label {
    font-size: 1rem;
    color: #333;
    margin-bottom: 5px;
    font-weight: 600;
}

.overview-detail {
    font-size: 0.9rem;
    color: #666;
}

.category-performance {
    margin-bottom: 30px;
}

.category-performance h3 {
    color: #333;
    margin-bottom: 20px;
    font-size: 1.4rem;
}

.category-performance-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 15px;
}

.category-performance-card {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    border-left: 4px solid #4CAF50;
}

.category-performance-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 15px;
}

.category-performance-header h4 {
    margin: 0;
    font-size: 1.1rem;
}

.performance-metrics {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
}

.metric {
    text-align: center;
}

.metric-label {
    display: block;
    font-size: 0.8rem;
    color: #888;
    margin-bottom: 2px;
}

.metric-value {
    display: block;
    font-size: 1.2rem;
    font-weight: bold;
    color: #333;
}

.recent-sessions {
    margin-bottom: 30px;
}

.recent-sessions h3 {
    color: #333;
    margin-bottom: 20px;
    font-size: 1.4rem;
}

.session-record {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 15px;
    border-left: 4px solid #4CAF50;
}

.session-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 15px;
}

.session-date {
    font-weight: bold;
    color: #333;
}

.session-mode {
    background: #e3f2fd;
    color: #1976d2;
    padding: 4px 8px;
    border-radius: 12px;
    font-size: 0.8rem;
}

.session-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 10px;
}

.session-stat {
    display: flex;
    align-items: center;
    gap: 5px;
    font-size: 0.9rem;
    color: #555;
}

.stat-icon {
    font-size: 1rem;
}

.no-data {
    text-align: center;
    color: #888;
    font-style: italic;
    padding: 20px;
}

.study-recommendations h3 {
    color: #333;
    margin-bottom: 20px;
    font-size: 1.4rem;
}

.recommendation-card {
    display: flex;
    align-items: flex-start;
    gap: 15px;
    background: #f8f9fa;
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 15px;
    border-left: 4px solid #ff9800;
}

.recommendation-icon {
    font-size: 2rem;
    flex-shrink: 0;
}

.recommendation-content h4 {
    margin: 0 0 8px 0;
    color: #333;
    font-size: 1.1rem;
}

.recommendation-content p {
    margin: 0;
    color: #666;
    line-height: 1.5;
}

/* 学习建议样式 */
.study-advice {
    background: #e8f5e8;
    padding: 20px;
    border-radius: 10px;
    border-left: 4px solid #4CAF50;
    margin-top: 15px;
}

.study-advice p {
    margin-bottom: 10px;
    line-height: 1.6;
}

.study-advice strong {
    color: #2e7d32;
}






/* 进度指示器 */
.progress-indicator {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 20px;
}

.progress-circle {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: conic-gradient(#4CAF50 0deg, #e0e0e0 0deg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    color: #333;
    position: relative;
}

.progress-circle::before {
    content: '';
    position: absolute;
    width: 45px;
    height: 45px;
    background: white;
    border-radius: 50%;
    z-index: 1;
}

.progress-circle span {
    position: relative;
    z-index: 2;
    font-size: 0.9rem;
}

/* 难度指示器 */
.difficulty-indicator {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 4px 8px;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
}

.difficulty-easy {
    background: #e8f5e8;
    color: #2e7d32;
}

.difficulty-medium {
    background: #fff3e0;
    color: #f57c00;
}

.difficulty-hard {
    background: #ffebee;
    color: #d32f2f;
}

/* 分类标签 */
.category-tag {
    display: inline-block;
    padding: 4px 12px;
    background: #e3f2fd;
    color: #1976d2;
    border-radius: 16px;
    font-size: 0.8rem;
    font-weight: 500;
    margin-bottom: 10px;
}

/* 时间显示 */
.time-display {
    font-family: 'Courier New', monospace;
    font-weight: bold;
    color: #666;
    background: rgba(255, 255, 255, 0.8);
    padding: 5px 10px;
    border-radius: 6px;
}

/* 成就徽章 */
.achievement-badge {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 6px 12px;
    background: linear-gradient(135deg, #ffd700, #ffed4e);
    color: #333;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(255, 215, 0, 0.3);
}

/* 响应式设计 */
@media (max-width: 768px) {
    .screen {
        padding: 15px;
    }

    .app-header h1 {
        font-size: 2rem;
    }

    .stats-container {
        gap: 8px;
        margin-bottom: 20px;
    }

    .stat-card {
        padding: 12px 8px;
    }

    .stat-number {
        font-size: 1.3rem;
    }

    .stat-label {
        font-size: 0.75rem;
    }

    .study-plan {
        padding: 15px;
        margin-bottom: 20px;
    }

    .study-plan h3 {
        margin-bottom: 12px;
        font-size: 1.1rem;
    }

    .plan-days {
        gap: 8px;
    }

    .plan-day {
        padding: 10px;
    }

    .day-header {
        margin-bottom: 5px;
        font-size: 0.9rem;
    }

    .quiz-header {
        padding: 10px 14px;
        margin-bottom: 18px;
        gap: 8px;
    }

    .btn-back {
        font-size: 0.95rem;
        padding: 5px 8px;
    }

    .quiz-progress {
        font-size: 0.95rem;
        padding: 5px 10px;
    }

    .quiz-timer {
        font-size: 0.9rem;
        padding: 5px 10px;
    }

    .question-container {
        padding: 20px;
        margin-bottom: 18px;
    }

    .question-number {
        font-size: 1rem;
        margin-bottom: 12px;
    }

    .question-text {
        font-size: 1.1rem;
    }

    .options-container {
        gap: 10px;
        margin-bottom: 20px;
    }

    .option {
        padding: 15px 18px;
        gap: 10px;
    }

    .option-label {
        width: 30px;
        height: 30px;
        font-size: 0.95rem;
    }

    .option-text {
        font-size: 1rem;
    }

    .question-actions {
        flex-direction: column;
        gap: 12px;
        margin-top: 12px;
    }

    .knowledge-categories {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .app-header h1 {
        font-size: 1.8rem;
    }

    .stats-container {
        gap: 6px;
        margin-bottom: 18px;
    }

    .stat-card {
        padding: 10px 6px;
        border-radius: 10px;
    }

    .stat-number {
        font-size: 1.2rem;
        margin-bottom: 2px;
    }

    .stat-label {
        font-size: 0.7rem;
    }

    .study-plan {
        padding: 12px;
        margin-bottom: 15px;
    }

    .study-plan h3 {
        margin-bottom: 10px;
        font-size: 1rem;
    }

    .plan-days {
        gap: 6px;
    }

    .plan-day {
        padding: 8px;
    }

    .day-header {
        margin-bottom: 4px;
        font-size: 0.85rem;
    }

    .progress-text {
        font-size: 0.75rem;
        min-width: 40px;
    }

    .estimated-time {
        font-size: 0.7rem;
        margin-top: 2px;
    }

    .quiz-header {
        padding: 8px 12px;
        margin-bottom: 15px;
        gap: 6px;
    }

    .btn-back {
        font-size: 0.9rem;
        padding: 4px 7px;
    }

    .quiz-progress {
        font-size: 0.9rem;
        padding: 4px 8px;
        min-width: 55px;
    }

    .quiz-timer {
        font-size: 0.85rem;
        padding: 4px 8px;
        min-width: 50px;
    }

    .question-container {
        padding: 18px;
        margin-bottom: 15px;
    }

    .question-number {
        font-size: 0.95rem;
        margin-bottom: 10px;
    }

    .question-text {
        font-size: 1rem;
        line-height: 1.4;
    }

    .options-container {
        gap: 8px;
        margin-bottom: 18px;
    }

    .option {
        padding: 14px 16px;
        gap: 8px;
    }

    .option-label {
        width: 28px;
        height: 28px;
        font-size: 0.9rem;
    }

    .option-text {
        font-size: 0.95rem;
        line-height: 1.3;
    }

    .question-actions {
        gap: 10px;
        margin-top: 10px;
    }

    .btn {
        padding: 12px 18px;
        font-size: 1rem;
    }

    .knowledge-category {
        padding: 20px;
    }

    .stats-content {
        padding: 20px;
    }
}

/* 极小屏幕优化 */
@media (max-width: 360px) {
    .quiz-header {
        padding: 3px 5px;
        margin-bottom: 5px;
        gap: 2px;
    }

    .btn-back {
        font-size: 0.75rem;
        padding: 1px 3px;
    }

    .quiz-progress {
        font-size: 0.7rem;
        padding: 1px 3px;
        min-width: 40px;
    }

    .quiz-timer {
        font-size: 0.65rem;
        padding: 1px 3px;
        min-width: 35px;
    }

    .question-container {
        padding: 10px;
        margin-bottom: 8px;
    }

    .question-number {
        font-size: 0.75rem;
        margin-bottom: 5px;
    }

    .question-text {
        font-size: 0.85rem;
        line-height: 1.2;
    }

    .options-container {
        gap: 4px;
        margin-bottom: 8px;
    }

    .option {
        padding: 6px 8px;
        gap: 4px;
    }

    .option-label {
        width: 20px;
        height: 20px;
        font-size: 0.7rem;
    }

    .option-text {
        font-size: 0.8rem;
        line-height: 1.1;
    }

    .question-actions {
        gap: 5px;
        margin-top: 5px;
    }

    .btn {
        padding: 6px 12px;
        font-size: 0.85rem;
    }
}