/* 关键词研究 - 研究论文风格样式 */

/* 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;
  --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;
  --content-width: 800px;
}

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

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

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

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

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

ul {
  list-style: none;
}

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

/* 容器 */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.content-wrap {
  max-width: var(--content-width);
  margin: 0 auto;
}

/* 头部 */
.header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  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: 1.25rem;
  font-weight: 700;
  color: var(--accent-color);
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo::before {
  content: "◆";
  color: var(--accent-color);
}

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

.nav a {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  font-weight: 500;
  transition: color 0.2s;
}

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

.search-box {
  position: relative;
}

.search-box input {
  width: 240px;
  padding: 8px 16px 8px 40px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  background: var(--bg-secondary);
  transition: all 0.2s;
}

.search-box input:focus {
  outline: none;
  border-color: var(--accent-color);
  width: 280px;
}

.search-box::before {
  content: "🔍";
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.875rem;
  opacity: 0.5;
}

/* Hero 区域 */
.hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  padding: 80px 0 60px;
  text-align: center;
}

.hero-title {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
  line-height: 1.3;
}

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 40px;
}

.hero-search {
  max-width: 560px;
  margin: 0 auto 48px;
  position: relative;
}

.hero-search input {
  width: 100%;
  padding: 16px 24px 16px 52px;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-lg);
  font-size: 1rem;
  background: var(--bg-primary);
  transition: all 0.2s;
}

.hero-search input:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 4px rgba(94, 53, 177, 0.1);
}

.hero-search::before {
  content: "🔍";
  position: absolute;
  left: 20px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.125rem;
  opacity: 0.5;
}

/* 研究区域 */
.research-areas {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  max-width: 720px;
  margin: 0 auto;
}

.area-card {
  background: var(--bg-primary);
  padding: 24px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
  transition: all 0.2s;
}

.area-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--accent-light);
}

.area-card h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent-color);
  margin-bottom: 8px;
}

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

/* 区块标题 */
.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;
}

/* 内容区块 */
.section {
  padding: 60px 0;
}

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

/* 论文/文章列表 */
.paper-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

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

.paper-item:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--accent-light);
}

.paper-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.paper-title a {
  color: inherit;
}

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

.paper-meta {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

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

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

.paper-abstract {
  font-size: 0.9375rem;
  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: 0.875rem;
  font-weight: 500;
  transition: all 0.2s;
  border: none;
  cursor: pointer;
}

.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);
}

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

/* 三栏推荐 */
.three-col-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

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

.article-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.article-list li {
  position: relative;
  padding-left: 16px;
}

.article-list li::before {
  content: "•";
  position: absolute;
  left: 0;
  color: var(--accent-color);
}

.article-list a {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  display: block;
  line-height: 1.5;
}

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

/* 面包屑 */
.breadcrumb {
  padding: 20px 0;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

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

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

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

/* 分类头部 */
.category-header {
  padding: 40px 0 32px;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 32px;
}

.category-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.category-count {
  font-size: 1rem;
  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-item {
  font-size: 0.875rem;
  color: var(--text-secondary);
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s;
}

.filter-item:hover,
.filter-item.active {
  background: var(--accent-color);
  color: white;
}

/* 分页 */
.pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 40px;
}

.pagination a,
.pagination span {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  font-size: 0.9375rem;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  transition: all 0.2s;
}

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

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

/* 文章详情页 */
.article-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 48px;
  padding: 40px 0;
}

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

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

.sidebar-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 16px;
}

.meta-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.meta-item {
  font-size: 0.875rem;
}

.meta-label {
  color: var(--text-muted);
  display: block;
  margin-bottom: 4px;
}

.meta-value {
  color: var(--text-primary);
  font-weight: 500;
}

.sidebar-actions {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sidebar-actions .btn {
  width: 100%;
  justify-content: center;
}

/* 文章主体 */
.article-header {
  margin-bottom: 32px;
}

.article-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.4;
  margin-bottom: 16px;
}

.article-authors {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.article-venue {
  font-size: 0.9375rem;
  color: var(--accent-color);
  font-weight: 500;
}

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

.abstract-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
}

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

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

.toc-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.toc-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toc-list a {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  display: block;
  padding: 4px 0;
}

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

/* 文章正文 */
.article-body {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-primary);
}

.article-body h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin: 40px 0 20px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-color);
}

.article-body h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 32px 0 16px;
}

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

.article-body ul,
.article-body ol {
  margin-bottom: 16px;
  padding-left: 24px;
}

.article-body li {
  margin-bottom: 8px;
  color: var(--text-secondary);
}

.article-body ul li {
  list-style: disc;
}

.article-body ol li {
  list-style: decimal;
}

/* 参考文献 */
.references {
  margin-top: 48px;
  padding-top: 32px;
  border-top: 2px solid var(--border-color);
}

.references-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 20px;
}

.reference-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.reference-item {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  padding-left: 24px;
  text-indent: -24px;
  line-height: 1.6;
}

/* 404 页面 */
.error-page {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 80px 24px;
}

.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: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.error-message {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  max-width: 400px;
}

/* 页脚 */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 48px 0 24px;
  margin-top: 80px;
}

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

.footer-brand {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--accent-color);
  margin-bottom: 12px;
}

.footer-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.footer-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

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

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* 响应式设计 */
@media (max-width: 992px) {
  .article-layout {
    grid-template-columns: 1fr;
    gap: 32px;
  }

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

  .article-main {
    order: 1;
  }

  .sidebar-actions {
    flex-direction: row;
  }

  .sidebar-actions .btn {
    width: auto;
  }

  .footer-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

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

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
    gap: 24px;
    padding-top: 12px;
    border-top: 1px solid var(--border-color);
  }

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

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

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

  .three-col-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }

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

  .article-title {
    font-size: 1.5rem;
  }

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

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

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

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

  .section {
    padding: 40px 0;
  }

  .hero {
    padding: 60px 0 40px;
  }

  .paper-item {
    padding: 20px;
  }

  .abstract-section {
    padding: 24px;
  }

  .pagination a,
  .pagination span {
    width: 36px;
    height: 36px;
    font-size: 0.875rem;
  }
}