/* 移动端优化样式 */
@media (max-width: 768px) {
  /* 优化导航栏 */
  nav ul {
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: center;
    padding: 0.5rem 0;
  }
  
  nav ul li {
    margin: 0.25rem;
  }
  
  nav ul li a {
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
  }
  
  /* 优化章节导航 */
  .nav-links {
    gap: 0.5rem;
  }
  
  .nav-link {
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
  }
  
  /* 优化按钮 */
  .btn {
    padding: 0.75rem 1.5rem;
    font-size: 0.9rem;
  }
  
  .cta-buttons {
    gap: 0.75rem;
  }
  
  /* 优化章节列表 */
  .chapter-columns {
    gap: 1rem;
  }
  
  .chapter-column h4 {
    font-size: 1.1rem;
  }
  
  /* 优化学习路径模块 */
  .modules {
    gap: 1rem;
  }
  
  .module-card {
    padding: 1rem;
  }
  
  .module-card h4 {
    font-size: 1.1rem;
  }
  
  /* 优化特征卡片 */
  .features-grid {
    gap: 1rem;
  }
  
  .feature-card {
    padding: 1rem;
  }
  
  .feature-card h3 {
    font-size: 1.2rem;
  }
  
  /* 优化知识结构项 */
  .structure-item {
    padding: 1rem;
  }
  
  .structure-item h3 {
    font-size: 1.2rem;
  }
  
  /* 移动端下拉菜单优化 */
  .dropdown {
    position: relative;
  }
  
  .dropdown-content {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: #fff;
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
    z-index: 1000;
    max-height: 400px;
    overflow-y: auto;
    display: none;
  }
  
  .dropdown.active .dropdown-content {
    display: block;
  }
  
  .dropdown-content a {
    padding: 10px 15px;
    font-size: 0.85rem;
  }
  
  .dropbtn {
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
  }
  
  /* 汉堡菜单按钮 */
  .mobile-menu-toggle {
    display: none;
    position: absolute;
    top: 15px;
    right: 15px;
    flex-direction: column;
    justify-content: space-between;
    width: 30px;
    height: 21px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 0;
    z-index: 1001;
  }
  
  .mobile-menu-toggle span {
    display: block;
    height: 3px;
    width: 100%;
    background-color: #333;
    border-radius: 3px;
    transition: all 0.3s;
  }
  
  /* 移动端导航菜单 */
  .mobile-nav-menu {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.9);
    z-index: 1000;
    flex-direction: column;
    justify-content: center;
    align-items: center;
  }
  
  .mobile-nav-menu.active {
    display: flex;
  }
  
  .mobile-nav-menu ul {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    max-height: 80vh;
    overflow-y: auto;
  }
  
  .mobile-nav-menu ul li {
    margin: 0.5rem 0;
    width: 80%;
    text-align: center;
  }
  
  .mobile-nav-menu ul li a {
    display: block;
    padding: 1rem;
    color: white;
    text-decoration: none;
    font-size: 1.2rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  }
  
  .mobile-nav-menu ul li a.active {
    color: #667eea;
  }
  
  .close-menu {
    position: absolute;
    top: 20px;
    right: 20px;
    color: white;
    font-size: 2rem;
    cursor: pointer;
  }
}

@media (max-width: 480px) {
  /* 进一步优化小屏幕显示 */
  nav ul {
    flex-direction: row;
    flex-wrap: wrap;
  }
  
  nav ul li {
    margin: 0.1rem;
  }
  
  nav ul li a {
    padding: 0.4rem 0.8rem;
    font-size: 0.8rem;
  }
  
  header h1 {
    font-size: 1.5rem;
  }
  
  header p {
    font-size: 0.9rem;
  }
  
  .hero h2 {
    font-size: 1.3rem;
  }
  
  .content-section h2 {
    font-size: 1.3rem;
  }
  
  .btn {
    padding: 0.6rem 1.2rem;
    font-size: 0.8rem;
  }
  
  .nav-link {
    padding: 0.4rem 0.8rem;
    font-size: 0.8rem;
  }
  
  .chapter-column h4 {
    font-size: 1rem;
  }
  
  .module-card h4 {
    font-size: 1rem;
  }
  
  .feature-card h3 {
    font-size: 1.1rem;
  }
  
  .structure-item h3 {
    font-size: 1.1rem;
  }
  
  /* 调整章节导航为滚动显示 */
  .nav-links {
    flex-wrap: nowrap;
    overflow-x: auto;
    justify-content: flex-start;
    padding: 0.5rem;
  }
  
  .nav-links::-webkit-scrollbar {
    height: 4px;
  }
  
  .nav-links::-webkit-scrollbar-thumb {
    background: #667eea;
    border-radius: 2px;
  }
  
  /* 移动端下拉菜单进一步优化 */
  .dropdown-content {
    max-height: 300px;
  }
  
  .dropdown-content a {
    padding: 8px 12px;
    font-size: 0.8rem;
  }
  
  .dropbtn {
    padding: 0.4rem 0.8rem;
    font-size: 0.8rem;
  }
  
  /* 小屏幕汉堡菜单 */
  .mobile-menu-toggle {
    display: flex;
  }
}