/* 跨境电商SEO - 研究论文风格样式 */
/* 主色调: #5e35b1 (深紫色) */

/* ===== CSS 变量 ===== */
:root {
  --accent-color: #5e35b1;
  --accent-light: #7e57c2;
  --accent-dark: #4527a0;
  --text-primary: #212121;
  --text-secondary: #616161;
  --text-muted: #9e9e9e;
  --bg-primary: #ffffff;
  --bg-secondary: #fafafa;
  --bg-tertiary: #f5f5f5;
  --border-color: #e0e0e0;
  --border-light: #eeeeee;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --max-width: 1200px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-serif: Georgia, "Times New Roman", serif;
}

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

html {
  font-size: 16px;
  line-height: 1.6;
}

body {
  font-family: var(--font-sans);
  color: var(--text-primary);
  background: var(--bg-primary);
  min-height: 100vh;
}

a {
  color: var(--accent-color);
  text-decoration: none;
  transition: color 0.2s;
}

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

ul, ol {
  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;
}

/* ===== 页头 ===== */
.header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-light);
  padding: 16px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-color);
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo span {
  color: var(--text-primary);
}

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

.nav a {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  padding: 8px 0;
  border-bottom: 2px solid transparent;
}

.nav a:hover,
.nav a.active {
  color: var(--accent-color);
  border-bottom-color: var(--accent-color);
}

.search-box {
  position: relative;
  width: 280px;
}

.search-box input {
  width: 100%;
  padding: 10px 40px 10px 16px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  background: var(--bg-secondary);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.search-box input:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(94, 53, 177, 0.1);
}

.search-box button {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
}

/* ===== Hero 区域 ===== */
.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;
  font-weight: 700;
  margin-bottom: 16px;
  letter-spacing: -0.5px;
}

.hero p {
  font-size: 1.2rem;
  opacity: 0.9;
  max-width: 600px;
  margin: 0 auto 32px;
}

.hero-search {
  max-width: 600px;
  margin: 0 auto;
}

.hero-search input {
  width: 100%;
  padding: 16px 24px;
  border: none;
  border-radius: var(--radius-lg);
  font-size: 1rem;
  box-shadow: var(--shadow-md);
}

.hero-search input::placeholder {
  color: var(--text-muted);
}

/* ===== 区域标题 ===== */
.section-title {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--accent-color);
  display: inline-block;
}

.section {
  padding: 48px 0;
}

.section-alt {
  background: var(--bg-secondary);
}

/* ===== 研究领域卡片 ===== */
.research-areas {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin-top: 24px;
}

.area-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: 24px;
  text-align: center;
  transition: transform 0.2s, box-shadow 0.2s;
}

.area-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.area-card h3 {
  font-size: 1.1rem;
  color: var(--accent-color);
  margin-bottom: 8px;
}

.area-card p {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

/* ===== 论文/文章列表 ===== */
.paper-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.paper-item {
  background: var(--bg-primary);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: box-shadow 0.2s;
}

.paper-item:hover {
  box-shadow: var(--shadow-sm);
}

.paper-title {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
  line-height: 1.4;
}

.paper-title a {
  color: inherit;
}

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

.paper-meta {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

.paper-meta span {
  margin-right: 16px;
}

.paper-meta .author {
  color: var(--accent-color);
  font-weight: 500;
}

.paper-abstract {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 16px;
}

.paper-actions {
  display: flex;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 500;
  transition: all 0.2s;
  cursor: pointer;
  border: none;
}

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

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

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background: var(--border-light);
  color: var(--text-primary);
}

/* ===== 三栏文章列表 ===== */
.three-columns {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.column h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-light);
}

.column ul li {
  padding: 10px 0;
  border-bottom: 1px solid var(--border-light);
}

.column ul li:last-child {
  border-bottom: none;
}

.column ul li a {
  color: var(--text-secondary);
  font-size: 0.9rem;
  display: block;
  line-height: 1.5;
}

.column ul li a:hover {
  color: var(--accent-color);
}

/* ===== 面包屑 ===== */
.breadcrumb {
  background: var(--bg-secondary);
  padding: 16px 0;
  border-bottom: 1px solid var(--border-light);
}

.breadcrumb ol {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
}

.breadcrumb li:not(:last-child)::after {
  content: ">";
  margin-left: 8px;
  color: var(--text-muted);
}

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

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

.breadcrumb li:last-child {
  color: var(--text-primary);
  font-weight: 500;
}

/* ===== 分类页头部 ===== */
.category-header {
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--border-light);
  margin-bottom: 32px;
}

.category-header h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 8px;
}

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

/* ===== 筛选器 ===== */
.filter-bar {
  display: flex;
  gap: 16px;
  margin-bottom: 24px;
  padding: 16px;
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
}

.filter-bar select {
  padding: 8px 16px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background: var(--bg-primary);
  font-size: 0.9rem;
  color: var(--text-secondary);
  cursor: pointer;
}

/* ===== 分页 ===== */
.pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border-light);
}

.pagination a,
.pagination span {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 500;
}

.pagination a {
  color: var(--text-secondary);
  background: var(--bg-secondary);
}

.pagination a:hover {
  background: var(--accent-color);
  color: white;
}

.pagination .current {
  background: var(--accent-color);
  color: white;
}

.pagination .prev,
.pagination .next {
  width: auto;
  padding: 0 16px;
}

/* ===== 文章详情页 ===== */
.article-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 48px;
  padding: 48px 0;
}

.article-sidebar {
  position: sticky;
  top: 100px;
  height: fit-content;
}

.sidebar-section {
  margin-bottom: 32px;
}

.sidebar-section h3 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-primary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent-color);
}

.sidebar-section p,
.sidebar-section li {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.sidebar-section ul li {
  padding: 4px 0;
}

.paper-info {
  background: var(--bg-secondary);
  padding: 20px;
  border-radius: var(--radius-md);
}

.paper-info-item {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid var(--border-light);
  font-size: 0.9rem;
}

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

.paper-info-item span:first-child {
  color: var(--text-muted);
}

.paper-info-item span:last-child {
  color: var(--text-primary);
  font-weight: 500;
}

/* ===== 文章正文 ===== */
.article-main {
  max-width: 800px;
}

.article-header {
  margin-bottom: 32px;
}

.article-header h1 {
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.article-meta span {
  display: flex;
  align-items: center;
  gap: 6px;
}

.article-actions {
  display: flex;
  gap: 12px;
  margin: 24px 0 32px;
}

/* ===== 摘要区块 ===== */
.abstract-box {
  background: var(--bg-secondary);
  border-left: 4px solid var(--accent-color);
  padding: 24px;
  margin-bottom: 32px;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.abstract-box h2 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--accent-color);
}

.abstract-box p {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-secondary);
}

/* ===== 关键词 ===== */
.keywords {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}

.keyword {
  display: inline-block;
  padding: 6px 12px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  color: var(--text-secondary);
}

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

/* ===== 目录 ===== */
.toc {
  background: var(--bg-secondary);
  padding: 24px;
  border-radius: var(--radius-md);
  margin-bottom: 32px;
}

.toc h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 16px;
}

.toc ol {
  counter-reset: toc;
  list-style: none;
}

.toc li {
  padding: 8px 0;
  border-bottom: 1px solid var(--border-light);
}

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

.toc a {
  color: var(--text-secondary);
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 8px;
}

.toc a::before {
  counter-increment: toc;
  content: counter(toc) ".";
  color: var(--accent-color);
  font-weight: 600;
  min-width: 24px;
}

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

/* ===== 文章正文内容 ===== */
.article-content {
  font-size: 1.05rem;
  line-height: 1.9;
  color: var(--text-primary);
}

.article-content h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin: 48px 0 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-light);
}

.article-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 32px 0 16px;
  color: var(--accent-color);
}

.article-content p {
  margin-bottom: 20px;
}

.article-content ul,
.article-content ol {
  margin-bottom: 20px;
  padding-left: 24px;
}

.article-content ul li {
  list-style: disc;
  margin-bottom: 8px;
}

.article-content ol li {
  list-style: decimal;
  margin-bottom: 8px;
}

.article-content blockquote {
  border-left: 4px solid var(--accent-color);
  padding-left: 20px;
  margin: 24px 0;
  color: var(--text-secondary);
  font-style: italic;
}

.article-content code {
  background: var(--bg-tertiary);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
  font-family: "SF Mono", Monaco, monospace;
  font-size: 0.9em;
}

.article-content pre {
  background: var(--bg-tertiary);
  padding: 20px;
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: 20px;
}

.article-content pre code {
  background: none;
  padding: 0;
}

/* ===== 404页面 ===== */
.error-page {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 80px 20px;
}

.error-code {
  font-size: 8rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 16px;
  opacity: 0.8;
}

.error-title {
  font-size: 1.75rem;
  font-weight: 600;
  margin-bottom: 16px;
}

.error-message {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  max-width: 500px;
}

/* ===== 页脚 ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-light);
  padding: 48px 0 24px;
  margin-top: 64px;
}

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

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

.footer-brand p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.footer-column h4 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.footer-column ul li {
  margin-bottom: 10px;
}

.footer-column ul li a {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.footer-column ul li a:hover {
  color: var(--accent-color);
}

.footer-bottom {
  border-top: 1px solid var(--border-light);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.footer-bottom a {
  color: var(--text-muted);
}

/* ===== 响应式设计 ===== */
@media (max-width: 1024px) {
  .article-layout {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .article-sidebar {
    position: static;
    order: 2;
  }

  .article-main {
    order: 1;
  }

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

@media (max-width: 768px) {
  .header .container {
    flex-wrap: wrap;
  }

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
    gap: 20px;
    padding-top: 12px;
    border-top: 1px solid var(--border-light);
  }

  .search-box {
    width: 200px;
  }

  .hero {
    padding: 48px 0;
  }

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

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

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

  .research-areas {
    grid-template-columns: 1fr;
  }

  .filter-bar {
    flex-wrap: wrap;
  }

  .article-header h1 {
    font-size: 1.5rem;
  }

  .article-content h2 {
    font-size: 1.25rem;
  }

  .article-content h3 {
    font-size: 1.1rem;
  }

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

  .footer-bottom {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }

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

@media (max-width: 480px) {
  .container {
    padding: 0 16px;
  }

  .paper-actions {
    flex-wrap: wrap;
  }

  .btn {
    padding: 6px 12px;
    font-size: 0.8rem;
  }

  .pagination a,
  .pagination span {
    width: 36px;
    height: 36px;
    font-size: 0.85rem;
  }
}