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

:root {
    --primary-color: #0066cc;
    --secondary-color: #004499;
    --success-color: #28a745;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
    --text-color: #333;
    --light-text: #666;
    --bg-color: #f5f5f5;
    --card-bg: #ffffff;
    --border-color: #ddd;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
}

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

/* 头部样式 */
header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 60px 0;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* 主内容区域 */
main {
    padding: 40px 0;
}

section {
    background: var(--card-bg);
    border-radius: 10px;
    padding: 30px;
    margin-bottom: 30px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

section h2 {
    color: var(--primary-color);
    margin-bottom: 25px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
    font-size: 1.8rem;
}

/* 学习进度卡片 */
.progress-card {
    background: linear-gradient(135deg, #fff, #f8f9fa);
}

.progress-bar {
    width: 100%;
    height: 40px;
    background-color: #e9ecef;
    border-radius: 20px;
    overflow: hidden;
    margin: 20px 0;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--success-color), #20c997);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
    transition: width 0.3s ease;
}

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

.progress-stats {
    display: flex;
    justify-content: space-around;
    margin-top: 20px;
}

.stat-item {
    text-align: center;
    padding: 15px;
    background: var(--bg-color);
    border-radius: 8px;
    min-width: 150px;
}

.stat-label {
    display: block;
    color: var(--light-text);
    font-size: 0.9rem;
    margin-bottom: 5px;
}

.stat-value {
    display: block;
    font-size: 1.8rem;
    font-weight: bold;
    color: var(--primary-color);
}

/* Week 章节 */
.week-section h2 {
    display: flex;
    align-items: center;
    gap: 10px;
}

/* Day 卡片网格 */
.day-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
}

.day-card {
    background: white;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    padding: 25px;
    text-align: center;
    transition: all 0.3s ease;
    cursor: pointer;
    text-decoration: none;
    color: var(--text-color);
}

.day-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0,0,0,0.1);
}

.day-card.completed {
    border-color: var(--success-color);
    background: linear-gradient(135deg, #fff, #f0fff4);
}

.day-card.locked {
    opacity: 0.7;
    cursor: not-allowed;
}

.day-card.completed:hover {
    box-shadow: 0 8px 16px rgba(40, 167, 69, 0.2);
}

.day-number {
    display: block;
    font-size: 1.3rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: 10px;
}

.day-card.completed .day-number {
    color: var(--success-color);
}

.day-title {
    display: block;
    font-size: 1rem;
    color: var(--text-color);
    margin-bottom: 10px;
}

.day-status {
    display: inline-block;
    padding: 5px 15px;
    border-radius: 20px;
    font-size: 0.85rem;
    background: var(--bg-color);
    color: var(--light-text);
}

.day-card.completed .day-status {
    background: var(--success-color);
    color: white;
}

/* 学习资源 */
.resource-list {
    list-style: none;
}

.resource-list li {
    margin-bottom: 15px;
}

.resource-list a {
    display: block;
    padding: 15px;
    background: var(--bg-color);
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-color);
    transition: all 0.3s ease;
}

.resource-list a:hover {
    background: var(--primary-color);
    color: white;
    transform: translateX(10px);
}

/* 页脚 */
footer {
    background: var(--text-color);
    color: white;
    text-align: center;
    padding: 30px 0;
    margin-top: 50px;
}

footer p {
    margin: 5px 0;
    opacity: 0.8;
}

/* Day 1 页面特定样式 */
.day-header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 40px 0;
    text-align: center;
    border-radius: 10px;
    margin-bottom: 30px;
}

.day-header h1 {
    font-size: 2.2rem;
    margin-bottom: 10px;
}

.day-header .meta {
    font-size: 1rem;
    opacity: 0.9;
}

.content-block {
    margin-bottom: 40px;
}

.content-block h3 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 1.5rem;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}

.content-block h4 {
    color: var(--secondary-color);
    margin-bottom: 10px;
    font-size: 1.2rem;
    margin-top: 20px;
}

.content-block p, .content-block ul {
    margin-bottom: 15px;
}

.content-block ul {
    padding-left: 20px;
}

.content-block li {
    margin-bottom: 10px;
}

.highlight-box {
    background: linear-gradient(135deg, #fff9e6, #fff3cd);
    border-left: 4px solid var(--warning-color);
    padding: 20px;
    border-radius: 8px;
    margin: 20px 0;
}

.highlight-box h4 {
    color: var(--warning-color);
    margin-bottom: 10px;
}

.key-points {
    background: var(--bg-color);
    padding: 20px;
    border-radius: 8px;
    margin: 20px 0;
}

.key-points h4 {
    color: var(--primary-color);
    margin-bottom: 15px;
}

.key-points ul {
    list-style: none;
    padding: 0;
}

.key-points li {
    padding: 8px 0;
    border-bottom: 1px dashed var(--border-color);
}

.key-points li:last-child {
    border-bottom: none;
}

.key-points li strong {
    color: var(--primary-color);
}

.faq-item {
    background: white;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 15px;
}

.faq-item h4 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.navigation {
    display: flex;
    justify-content: space-between;
    margin-top: 40px;
    padding-top: 30px;
    border-top: 2px solid var(--border-color);
}

.nav-btn {
    display: inline-block;
    padding: 12px 30px;
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 25px;
    transition: all 0.3s ease;
}

.nav-btn:hover {
    background: var(--secondary-color);
    transform: translateY(-2px);
}

.nav-btn.disabled {
    background: var(--border-color);
    cursor: not-allowed;
}

/* 响应式设计 */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .progress-stats {
        flex-direction: column;
        gap: 10px;
    }

    .day-grid {
        grid-template-columns: 1fr;
    }

    section {
        padding: 20px;
    }
}