:root {
  --accent-color: #00bcd4;
  --accent-dark: #0097a7;
  --bg-primary: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-card: #0f3460;
  --text-primary: #ffffff;
  --text-secondary: #b8c5d6;
  --text-muted: #8892b0;
  --border-color: rgba(0, 188, 212, 0.2);
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
  --shadow-accent: 0 4px 20px rgba(0, 188, 212, 0.2);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

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

a:hover {
  color: var(--text-primary);
}

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

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

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

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

.nav {
  display: flex;
  gap: 2rem;
}

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

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

/* Main Container */
.main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
}

/* Split Screen Layout */
.split-screen {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  min-height: 500px;
  margin: 2rem 0;
}

.split-panel {
  background: var(--bg-card);
  border-radius: 12px;
  padding: 3rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  border: 1px solid var(--border-color);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.split-panel:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-accent);
}

.split-panel h2 {
  font-size: 2rem;
  margin-bottom: 1rem;
  color: var(--accent-color);
}

.split-panel p {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  line-height: 1.8;
}

.cta-button {
  display: inline-block;
  background: var(--accent-color);
  color: var(--bg-primary);
  padding: 0.875rem 2rem;
  border-radius: 6px;
  font-weight: 600;
  transition: all 0.3s ease;
  align-self: flex-start;
}

.cta-button:hover {
  background: var(--accent-dark);
  color: var(--text-primary);
  transform: translateY(-2px);
}

/* Section Title */
.section-title {
  font-size: 1.5rem;
  color: var(--accent-color);
  margin: 3rem 0 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--border-color);
}

/* Article Grid */
.article-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  margin: 2rem 0;
}

.article-column {
  background: var(--bg-card);
  border-radius: 8px;
  padding: 1.5rem;
  border: 1px solid var(--border-color);
}

.article-column h3 {
  font-size: 1.1rem;
  color: var(--accent-color);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-color);
}

.article-list {
  list-style: none;
}

.article-list li {
  padding: 0.75rem 0;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

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

.article-list a {
  color: var(--text-secondary);
  display: block;
  transition: all 0.3s ease;
}

.article-list a:hover {
  color: var(--accent-color);
  padding-left: 0.5rem;
}

.article-list .meta {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

/* Breadcrumb */
.breadcrumb {
  background: var(--bg-secondary);
  padding: 1rem 2rem;
  margin: 0 -2rem 2rem;
  border-bottom: 1px solid var(--border-color);
}

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

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

.breadcrumb span {
  color: var(--text-secondary);
  margin: 0 0.5rem;
}

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

/* Category Grid */
.category-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2rem;
  margin: 2rem 0;
}

.category-card {
  background: var(--bg-card);
  border-radius: 12px;
  padding: 2rem;
  border: 1px solid var(--border-color);
}

.category-card h3 {
  font-size: 1.3rem;
  color: var(--accent-color);
  margin-bottom: 1rem;
}

.category-items {
  list-style: none;
  margin-bottom: 1.5rem;
}

.category-items li {
  padding: 0.5rem 0;
  color: var(--text-secondary);
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

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

.view-all {
  display: inline-block;
  color: var(--accent-color);
  font-weight: 500;
  font-size: 0.9rem;
}

.view-all:hover {
  text-decoration: underline;
}

/* Related Articles */
.related-section {
  background: var(--bg-secondary);
  border-radius: 12px;
  padding: 2rem;
  margin: 2rem 0;
  border: 1px solid var(--border-color);
}

.related-section h3 {
  color: var(--accent-color);
  margin-bottom: 1rem;
}

.related-list {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

.related-list a {
  background: var(--bg-card);
  padding: 0.5rem 1rem;
  border-radius: 20px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  transition: all 0.3s ease;
}

.related-list a:hover {
  background: var(--accent-color);
  color: var(--bg-primary);
  border-color: var(--accent-color);
}

/* Article Content */
.article-content {
  background: var(--bg-card);
  border-radius: 12px;
  padding: 3rem;
  margin: 2rem 0;
  border: 1px solid var(--border-color);
}

.article-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.article-header h1 {
  font-size: 2.5rem;
  color: var(--accent-color);
  margin-bottom: 1rem;
  line-height: 1.3;
}

.article-meta {
  display: flex;
  gap: 2rem;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.article-body {
  color: var(--text-secondary);
  line-height: 1.9;
}

.article-body h2 {
  color: var(--accent-color);
  margin: 2rem 0 1rem;
  font-size: 1.5rem;
}

.article-body h3 {
  color: var(--text-primary);
  margin: 1.5rem 0 0.75rem;
  font-size: 1.2rem;
}

.article-body p {
  margin-bottom: 1.25rem;
}

.article-body ul,
.article-body ol {
  margin: 1rem 0 1.5rem 2rem;
}

.article-body li {
  margin-bottom: 0.5rem;
}

/* 404 Page */
.error-page {
  text-align: center;
  padding: 6rem 2rem;
}

.error-code {
  font-size: 8rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 1rem;
  text-shadow: 0 0 40px rgba(0, 188, 212, 0.3);
}

.error-title {
  font-size: 2rem;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.error-message {
  color: var(--text-secondary);
  margin-bottom: 2rem;
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
}

.error-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
}

.btn-secondary {
  display: inline-block;
  background: transparent;
  color: var(--accent-color);
  padding: 0.875rem 2rem;
  border-radius: 6px;
  font-weight: 600;
  border: 2px solid var(--accent-color);
  transition: all 0.3s ease;
}

.btn-secondary:hover {
  background: var(--accent-color);
  color: var(--bg-primary);
}

/* Footer */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 3rem 0 2rem;
  margin-top: 4rem;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
}

.footer-section h4 {
  color: var(--accent-color);
  margin-bottom: 1rem;
  font-size: 1rem;
}

.footer-section p,
.footer-section a {
  color: var(--text-muted);
  font-size: 0.9rem;
  line-height: 1.8;
}

.footer-section a {
  display: block;
  margin-bottom: 0.5rem;
}

.footer-bottom {
  max-width: 1200px;
  margin: 2rem auto 0;
  padding: 2rem 2rem 0;
  border-top: 1px solid var(--border-color);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* Responsive Design */
@media (max-width: 968px) {
  .split-screen {
    grid-template-columns: 1fr;
    min-height: auto;
  }

  .split-panel {
    padding: 2rem;
  }

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

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

  .footer-content {
    grid-template-columns: 1fr;
    text-align: center;
  }
}

@media (max-width: 640px) {
  .header-content {
    flex-direction: column;
    gap: 1rem;
  }

  .nav {
    gap: 1rem;
  }

  .main {
    padding: 1rem;
  }

  .split-panel {
    padding: 1.5rem;
  }

  .split-panel h2 {
    font-size: 1.5rem;
  }

  .article-content {
    padding: 1.5rem;
  }

  .article-header h1 {
    font-size: 1.75rem;
  }

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

  .error-actions {
    flex-direction: column;
    align-items: center;
  }

  .breadcrumb {
    margin: 0 -1rem 2rem;
    padding: 1rem;
  }
}

/* SEO Hidden Keywords */
.seo-keywords {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}