/* ===== CSS 变量 ===== */
:root {
  --accent-color: #4caf50;
  --accent-dark: #388e3c;
  --accent-light: #c8e6c9;
  --text-primary: #212121;
  --text-secondary: #757575;
  --bg-primary: #ffffff;
  --bg-secondary: #f5f5f5;
  --border-color: #e0e0e0;
  --shadow: 0 2px 8px rgba(0,0,0,0.1);
  --radius: 8px;
  --max-width: 1200px;
  --header-height: 64px;
}

/* ===== 重置样式 ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

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

a {
  text-decoration: none;
  color: var(--accent-color);
  transition: color 0.3s;
}

a:hover {
  color: var(--accent-dark);
}

ul {
  list-style: none;
}

img {
  max-width: 100%;
  height: auto;
}

/* ===== 布局容器 ===== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Header ===== */
.header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-color);
}

.nav {
  display: flex;
  gap: 32px;
}

.nav a {
  color: var(--text-primary);
  font-weight: 500;
}

.nav a:hover {
  color: var(--accent-color);
}

.search-box {
  display: flex;
  align-items: center;
  gap: 8px;
}

.search-box input {
  padding: 8px 16px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  font-size: 0.875rem;
  width: 200px;
}

.search-box button {
  padding: 8px 16px;
  background: var(--accent-color);
  color: white;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.875rem;
}

.search-box button:hover {
  background: var(--accent-dark);
}

/* ===== Hero Section ===== */
.hero {
  background: linear-gradient(135deg, var(--accent-color) 0%, var(--accent-dark) 100%);
  color: white;
  padding: 80px 0;
  text-align: center;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 16px;
}

.hero p {
  font-size: 1.125rem;
  opacity: 0.9;
  max-width: 600px;
  margin: 0 auto;
}

/* ===== Section 标题 ===== */
.section-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 24px;
  text-align: center;
}

/* ===== 分类卡片 ===== */
.categories {
  padding: 64px 0;
  background: var(--bg-secondary);
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.category-card {
  background: var(--bg-primary);
  padding: 32px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
  transition: transform 0.3s, box-shadow 0.3s;
}

.category-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.15);
}

.category-card h3 {
  color: var(--accent-color);
  margin-bottom: 12px;
  font-size: 1.25rem;
}

.category-card p {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

/* ===== 指南列表 ===== */
.guidelines {
  padding: 64px 0;
}

.guideline-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 800px;
  margin: 0 auto;
}

.guideline-item {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: border-color 0.3s;
}

.guideline-item:hover {
  border-color: var(--accent-color);
}

.guideline-item h4 {
  font-size: 1.125rem;
  margin-bottom: 4px;
}

.guideline-item span {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.btn {
  padding: 10px 20px;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s;
  border: none;
}

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

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

.btn-outline {
  background: transparent;
  border: 1px solid var(--accent-color);
  color: var(--accent-color);
}

.btn-outline:hover {
  background: var(--accent-color);
  color: white;
}

/* ===== 快速参考 ===== */
.quick-ref {
  padding: 48px 0;
  background: var(--accent-light);
  text-align: center;
}

.quick-ref h3 {
  margin-bottom: 16px;
}

/* ===== 文章列表 ===== */
.articles {
  padding: 64px 0;
  background: var(--bg-secondary);
}

.article-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.article-col h4 {
  font-size: 1rem;
  color: var(--accent-color);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent-light);
}

.article-col li {
  padding: 8px 0;
  border-bottom: 1px solid var(--border-color);
}

.article-col li:last-child {
  border-bottom: none;
}

.article-col a {
  color: var(--text-primary);
  font-size: 0.9375rem;
}

.article-col a:hover {
  color: var(--accent-color);
}

/* ===== Footer ===== */
.footer {
  background: var(--text-primary);
  color: white;
  padding: 48px 0 24px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 32px;
}

.footer-brand p {
  color: #aaa;
  margin-top: 16px;
  font-size: 0.875rem;
}

.footer-links h5 {
  font-size: 0.875rem;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.footer-links li {
  margin-bottom: 8px;
}

.footer-links a {
  color: #aaa;
  font-size: 0.875rem;
}

.footer-links a:hover {
  color: white;
}

.footer-bottom {
  border-top: 1px solid #444;
  padding-top: 24px;
  text-align: center;
  color: #aaa;
  font-size: 0.875rem;
}

/* ===== 面包屑 ===== */
.breadcrumb {
  background: var(--bg-secondary);
  padding: 16px 0;
  font-size: 0.875rem;
}

.breadcrumb a {
  color: var(--text-secondary);
}

.breadcrumb a:hover {
  color: var(--accent-color);
}

.breadcrumb span {
  color: var(--text-primary);
  margin: 0 8px;
}

/* ===== 页面头部 ===== */
.page-header {
  background: var(--bg-secondary);
  padding: 48px 0;
  text-align: center;
}

.page-header h1 {
  font-size: 2rem;
  margin-bottom: 8px;
}

.page-header p {
  color: var(--text-secondary);
}

/* ===== 指南详情 ===== */
.guideline-detail {
  padding: 48px 0;
}

.guideline-meta {
  text-align: center;
  margin-bottom: 32px;
}

.guideline-meta span {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.guideline-section {
  max-width: 800px;
  margin: 0 auto 48px;
}

.guideline-section h2 {
  font-size: 1.25rem;
  margin-bottom: 16px;
  color: var(--accent-color);
}

.guideline-section p {
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.principle-list {
  background: var(--bg-secondary);
  border-radius: var(--radius);
  overflow: hidden;
}

.principle-item {
  padding: 20px 24px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

.principle-item:last-child {
  border-bottom: none;
}

.principle-item::before {
  content: "✓";
  color: var(--accent-color);
  font-weight: bold;
  flex-shrink: 0;
}

.example-box {
  background: var(--bg-secondary);
  padding: 24px;
  border-radius: var(--radius);
  margin-bottom: 16px;
  border-left: 4px solid var(--accent-color);
}

.example-box.do {
  border-left-color: var(--accent-color);
}

.example-box.dont {
  border-left-color: #f44336;
}

.example-box h4 {
  font-size: 0.875rem;
  margin-bottom: 8px;
  text-transform: uppercase;
}

.resource-list li {
  padding: 8px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.resource-list li::before {
  content: "•";
  color: var(--accent-color);
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.related-card {
  background: var(--bg-secondary);
  padding: 20px;
  border-radius: var(--radius);
  text-align: center;
}

.related-card h5 {
  font-size: 0.9375rem;
  margin-bottom: 4px;
}

.related-card span {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

/* ===== 404 页面 ===== */
.error-page {
  min-height: calc(100vh - var(--header-height) - 300px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 64px 20px;
}

.error-code {
  font-size: 8rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 16px;
}

.error-page h1 {
  font-size: 1.5rem;
  margin-bottom: 16px;
}

.error-page p {
  color: var(--text-secondary);
  margin-bottom: 32px;
}

/* ===== 响应式设计 ===== */
@media (max-width: 992px) {
  .article-grid {
    grid-template-columns: 1fr;
  }

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

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

@media (max-width: 768px) {
  .header .container {
    flex-wrap: wrap;
    height: auto;
    padding: 16px 20px;
    gap: 16px;
  }

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
    gap: 20px;
  }

  .search-box {
    order: 2;
  }

  .search-box input {
    width: 150px;
  }

  .hero {
    padding: 48px 0;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .hero p {
    font-size: 1rem;
  }

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

  .guideline-item {
    flex-direction: column;
    align-items: flex-start;
    gap: 12px;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .error-code {
    font-size: 5rem;
  }
}

@media (max-width: 480px) {
  .nav {
    flex-wrap: wrap;
  }

  .search-box input {
    width: 120px;
  }
}