/* 全局重置与基础样式 - SEO友好，响应式布局 */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

:root {
  --primary: #0088cc;
  --secondary: #006699;
  --light: #f5f7fa;
  --dark: #2c3e50;
  --white: #ffffff;
  --gray: #7f8c8d;
}

body {
  background-color: var(--light);
  color: var(--dark);
  line-height: 1.6;
}

/* 导航栏 */
.navbar {
  background-color: var(--primary);
  padding: 1rem 2rem;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

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

.logo {
  color: var(--white);
  font-size: 1.5rem;
  font-weight: bold;
  text-decoration: none;
}

.nav-links a {
  color: var(--white);
  text-decoration: none;
  margin-left: 1.5rem;
  font-size: 1rem;
  transition: 0.3s;
}

.nav-links a:hover, .nav-links a.active {
  color: #e3f2fd;
  text-decoration: underline;
}

/* 容器通用样式 */
.container {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 1rem;
}

/* 标题样式 - SEO优化层级 */
h1 {
  font-size: 2.2rem;
  color: var(--primary);
  margin-bottom: 1rem;
  text-align: center;
}

h2 {
  font-size: 1.8rem;
  color: var(--secondary);
  margin: 1.5rem 0 1rem;
  border-left: 4px solid var(--primary);
  padding-left: 0.8rem;
}

h3 {
  font-size: 1.4rem;
  color: var(--dark);
  margin: 1rem 0;
}

p {
  font-size: 1rem;
  margin-bottom: 1rem;
  color: var(--dark);
}

/* 按钮样式 */
.btn {
  display: inline-block;
  padding: 0.8rem 1.5rem;
  background-color: var(--primary);
  color: var(--white);
  text-decoration: none;
  border-radius: 5px;
  transition: 0.3s;
  border: none;
  cursor: pointer;
  font-size: 1rem;
}

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

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

/* 卡片布局 */
.card-group {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 2rem 0;
}

.card {
  background: var(--white);
  padding: 1.5rem;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  transition: 0.3s;
}

.card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.12);
}

.card img {
  width: 100%;
  height: 180px;
  object-fit: cover;
  border-radius: 5px;
  margin-bottom: 1rem;
}

/* 列表样式 */
ul, ol {
  margin-left: 1.8rem;
  margin-bottom: 1rem;
}

li {
  margin-bottom: 0.5rem;
}

/* 表格样式 */
.table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  background: var(--white);
}

.table th, .table td {
  padding: 1rem;
  text-align: left;
  border-bottom: 1px solid #ddd;
}

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

/* 页脚 */
.footer {
  background-color: var(--dark);
  color: var(--white);
  padding: 2rem 0;
  margin-top: 3rem;
  text-align: center;
}

.footer p {
  color: var(--white);
  margin-bottom: 0.5rem;
}

/* 响应式适配 */
@media (max-width: 768px) {
  .nav-container {
    flex-direction: column;
    gap: 1rem;
  }
  
  .nav-links a {
    margin: 0 0.8rem;
  }
  
  h1 {
    font-size: 1.8rem;
  }
}