/* ===== CSS Variables ===== */
:root {
  --accent-color: #673ab7;
  --accent-light: #7e57c2;
  --accent-dark: #512da8;
  --text-primary: #333;
  --text-secondary: #666;
  --text-muted: #999;
  --bg-primary: #fff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #f0f0f0;
  --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;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

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

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

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

/* ===== Layout ===== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-sm);
}

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

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

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

.nav {
  display: flex;
  gap: var(--spacing-md);
}

.nav a {
  color: var(--text-secondary);
  font-weight: 500;
  padding: 0.5rem 0;
}

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

.search-box {
  display: flex;
  align-items: center;
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  padding: 0.5rem 1rem;
  min-width: 240px;
}

.search-box input {
  border: none;
  background: transparent;
  outline: none;
  width: 100%;
  font-size: 0.875rem;
}

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

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

.hero h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-sm);
}

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

.hero-search {
  max-width: 500px;
  margin: 0 auto;
}

.hero-search input {
  width: 100%;
  padding: 1rem 1.5rem;
  border: none;
  border-radius: var(--radius-lg);
  font-size: 1rem;
  box-shadow: var(--shadow-md);
}

/* ===== Section Title ===== */
.section-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

/* ===== Categories ===== */
.categories {
  padding: var(--spacing-xl) 0;
  background: var(--bg-secondary);
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
}

.category-card {
  background: var(--bg-primary);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
}

.category-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.category-card h3 {
  font-size: 1.125rem;
  color: var(--accent-color);
  margin-bottom: 0.5rem;
}

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

/* ===== Whitepaper Cards ===== */
.whitepapers {
  padding: var(--spacing-xl) 0;
}

.wp-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.wp-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  display: flex;
  gap: var(--spacing-md);
  transition: box-shadow 0.2s;
}

.wp-card:hover {
  box-shadow: var(--shadow-md);
}

.wp-icon {
  width: 80px;
  height: 100px;
  background: linear-gradient(135deg, var(--accent-light), var(--accent-color));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 1.5rem;
  font-weight: 700;
  flex-shrink: 0;
}

.wp-content {
  flex: 1;
}

.wp-content h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.wp-meta {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: var(--spacing-sm);
}

.wp-meta span {
  margin-right: var(--spacing-sm);
}

.wp-actions {
  display: flex;
  gap: var(--spacing-sm);
}

.btn {
  display: inline-flex;
  align-items: center;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  transition: all 0.2s;
  cursor: pointer;
  border: none;
}

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

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

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

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

/* ===== Sidebar Sections ===== */
.sidebar-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
  padding: var(--spacing-xl) 0;
  background: var(--bg-secondary);
}

.sidebar-section {
  background: var(--bg-primary);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}

.sidebar-section h4 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  padding-bottom: var(--spacing-xs);
  border-bottom: 2px solid var(--accent-color);
  display: inline-block;
}

.sidebar-section ul {
  list-style: none;
}

.sidebar-section li {
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border-color);
}

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

.sidebar-section a {
  color: var(--text-secondary);
  font-size: 0.875rem;
  display: block;
}

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

/* ===== Breadcrumb ===== */
.breadcrumb {
  padding: var(--spacing-sm) 0;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
}

.breadcrumb ol {
  display: flex;
  list-style: none;
  gap: 0.5rem;
  font-size: 0.875rem;
}

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

.breadcrumb li:last-child {
  color: var(--text-muted);
}

.breadcrumb li:not(:last-child)::after {
  content: ">";
  margin-left: 0.5rem;
  color: var(--text-muted);
}

/* ===== Page Header ===== */
.page-header {
  padding: var(--spacing-lg) 0;
  background: var(--bg-secondary);
  text-align: center;
}

.page-header h1 {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

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

/* ===== Sort Bar ===== */
.sort-bar {
  display: flex;
  justify-content: flex-end;
  padding: var(--spacing-sm) 0;
  gap: var(--spacing-sm);
  font-size: 0.875rem;
}

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

.sort-bar a.active {
  color: var(--accent-color);
  font-weight: 500;
}

/* ===== Pagination ===== */
.pagination {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  padding: var(--spacing-lg) 0;
}

.pagination a,
.pagination span {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
}

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

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

.pagination .current {
  background: var(--accent-color);
  color: #fff;
  font-weight: 500;
}

/* ===== Article Page ===== */
.article-header {
  padding: var(--spacing-xl) 0 var(--spacing-lg);
  text-align: center;
  border-bottom: 1px solid var(--border-color);
}

.article-header h1 {
  font-size: 2rem;
  margin-bottom: var(--spacing-sm);
}

.article-meta {
  color: var(--text-muted);
  font-size: 0.875rem;
}

.article-meta span {
  margin: 0 var(--spacing-sm);
}

.article-cover {
  max-width: 600px;
  margin: var(--spacing-lg) auto;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.article-cover img {
  width: 100%;
}

.article-content {
  max-width: 800px;
  margin: 0 auto;
  padding: var(--spacing-lg) 0;
}

.article-section {
  margin-bottom: var(--spacing-xl);
}

.article-section h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
  color: var(--accent-color);
}

.article-section p {
  margin-bottom: var(--spacing-sm);
  color: var(--text-secondary);
  line-height: 1.8;
}

.key-points-list {
  list-style: none;
}

.key-points-list li {
  padding: var(--spacing-sm) 0;
  padding-left: 1.5rem;
  position: relative;
  border-bottom: 1px solid var(--border-color);
}

.key-points-list li::before {
  content: "•";
  color: var(--accent-color);
  font-weight: bold;
  position: absolute;
  left: 0;
}

.key-points-list li:last-child {
  border-bottom: none;
}

.key-points-list strong {
  color: var(--text-primary);
  display: block;
  margin-bottom: 0.25rem;
}

.toc {
  background: var(--bg-secondary);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
}

.toc h3 {
  font-size: 1.125rem;
  margin-bottom: var(--spacing-sm);
}

.toc ol {
  padding-left: 1.5rem;
}

.toc li {
  padding: 0.25rem 0;
  color: var(--text-secondary);
}

/* ===== Related Section ===== */
.related-section {
  background: var(--bg-secondary);
  padding: var(--spacing-xl) 0;
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
}

.related-card {
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s;
}

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

.related-card .wp-icon {
  width: 100%;
  height: 120px;
  border-radius: 0;
}

.related-card h4 {
  padding: var(--spacing-sm);
  font-size: 0.9375rem;
  color: var(--text-primary);
}

/* ===== 404 Page ===== */
.error-page {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--spacing-xl);
}

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

.error-page h1 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

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

/* ===== Footer ===== */
.footer {
  background: var(--bg-tertiary);
  padding: var(--spacing-lg) 0;
  border-top: 1px solid var(--border-color);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer p {
  color: var(--text-muted);
  font-size: 0.875rem;
}

.footer-links {
  display: flex;
  gap: var(--spacing-md);
}

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

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding: var(--spacing-sm) 0;
    gap: var(--spacing-sm);
  }

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
    gap: var(--spacing-sm);
  }

  .search-box {
    min-width: auto;
    flex: 1;
  }

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

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

  .wp-card {
    flex-direction: column;
  }

  .wp-icon {
    width: 100%;
    height: 80px;
  }

  .footer-inner {
    flex-direction: column;
    gap: var(--spacing-sm);
    text-align: center;
  }
}