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

:root {
  --bg-primary: #0a0f1e;
  --bg-secondary: #0d1424;
  --bg-card: #111827;
  --bg-card-hover: #1a2540;
  --bg-code: #1e293b;
  --color-primary: #3b82f6;
  --color-primary-light: #60a5fa;
  --color-secondary: #06b6d4;
  --color-accent: #8b5cf6;
  --text-primary: #e2e8f0;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border-color: #1e3a5f;
  --border-glow: rgba(59, 130, 246, 0.3);
  --nav-height: 64px;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', Consolas, monospace;
  --radius: 8px;
  --radius-lg: 12px;
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.4);
  --transition: 0.2s ease;
}

html {
  scroll-behavior: smooth;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-sans);
  line-height: 1.6;
  min-height: 100vh;
}

a {
  color: var(--color-primary-light);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-secondary);
}

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

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb { background: var(--border-color); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--color-primary); }

/* ===== Navigation ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(10, 15, 30, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  display: flex;
  align-items: center;
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-logo .logo-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  color: #fff;
}

.nav-logo span.brand {
  background: linear-gradient(90deg, var(--color-primary-light), var(--color-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.9rem;
  padding: 6px 14px;
  border-radius: var(--radius);
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--text-primary);
  background: rgba(59, 130, 246, 0.1);
}

.nav-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
  padding: 4px;
}

/* ===== Page Wrapper ===== */
.page-wrapper {
  padding-top: var(--nav-height);
}

/* ===== Hero Section ===== */
.hero {
  padding: 100px 24px 80px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.08) 0%, transparent 70%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(59, 130, 246, 0.1);
  border: 1px solid rgba(59, 130, 246, 0.3);
  color: var(--color-primary-light);
  padding: 6px 16px;
  border-radius: 100px;
  font-size: 0.85rem;
  margin-bottom: 24px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  background: linear-gradient(135deg, #fff 30%, var(--color-primary-light) 70%, var(--color-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 40px;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 48px;
  flex-wrap: wrap;
}

.hero-stat {
  text-align: center;
}

.hero-stat .number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-primary-light);
  display: block;
}

.hero-stat .label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ===== Section ===== */
.section {
  max-width: 1200px;
  margin: 0 auto;
  padding: 60px 24px;
}

.section-header {
  margin-bottom: 40px;
}

.section-label {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  margin-bottom: 8px;
}

.section-title {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* ===== Tag Filters ===== */
.tag-filters {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}

.tag-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 6px 16px;
  border-radius: 100px;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition);
}

.tag-btn:hover,
.tag-btn.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}

/* ===== Article Grid ===== */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 24px;
}

.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  transition: all var(--transition);
  cursor: pointer;
  text-decoration: none;
  color: inherit;
  position: relative;
  overflow: hidden;
}

.article-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
  opacity: 0;
  transition: opacity var(--transition);
}

.article-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-glow);
  box-shadow: 0 0 30px rgba(59, 130, 246, 0.1);
  transform: translateY(-2px);
}

.article-card:hover::before {
  opacity: 1;
}

.card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.card-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  flex-shrink: 0;
}

.card-icon.flutter { background: rgba(59, 130, 246, 0.15); }
.card-icon.react-native { background: rgba(6, 182, 212, 0.15); }
.card-icon.general { background: rgba(139, 92, 246, 0.15); }

.card-number {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.card-tag {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 100px;
  font-size: 0.75rem;
  font-weight: 600;
}

.card-tag.flutter {
  background: rgba(59, 130, 246, 0.15);
  color: var(--color-primary-light);
}

.card-tag.react-native {
  background: rgba(6, 182, 212, 0.15);
  color: var(--color-secondary);
}

.card-tag.general {
  background: rgba(139, 92, 246, 0.15);
  color: #a78bfa;
}

.card-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.5;
}

.card-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
  flex: 1;
}

.card-meta {
  display: flex;
  align-items: center;
  gap: 16px;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.card-meta span {
  display: flex;
  align-items: center;
  gap: 4px;
}

/* ===== About Section ===== */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: center;
}

.about-text p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  line-height: 1.8;
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 20px;
}

.skill-tag {
  background: var(--bg-code);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 4px 12px;
  border-radius: var(--radius);
  font-size: 0.82rem;
  font-family: var(--font-mono);
}

.about-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 32px;
}

.about-stat-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.about-stat-list li {
  display: flex;
  align-items: center;
  gap: 16px;
}

.stat-bar-wrap {
  flex: 1;
}

.stat-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  margin-bottom: 6px;
  color: var(--text-secondary);
}

.stat-bar {
  height: 6px;
  background: var(--bg-code);
  border-radius: 3px;
  overflow: hidden;
}

.stat-fill {
  height: 100%;
  border-radius: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
  transition: width 1s ease;
}

/* ===== Footer ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 40px 24px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.875rem;
}

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

/* ===== Article Page Layout ===== */
.article-layout {
  max-width: 1200px;
  margin: 0 auto;
  padding: 40px 24px;
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 48px;
  align-items: start;
}

/* ===== TOC Sidebar ===== */
.toc-sidebar {
  position: sticky;
  top: calc(var(--nav-height) + 24px);
}

.toc-title {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.toc-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.toc-list a {
  display: block;
  padding: 6px 12px;
  border-left: 2px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.85rem;
  transition: all var(--transition);
}

.toc-list a:hover,
.toc-list a.active {
  border-left-color: var(--color-primary);
  color: var(--color-primary-light);
  background: rgba(59, 130, 246, 0.05);
}

.toc-list .toc-h3 a {
  padding-left: 24px;
  font-size: 0.8rem;
}

/* ===== Article Content ===== */
.article-main {}

.article-header {
  margin-bottom: 40px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--border-color);
}

.article-meta-top {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.article-meta-top .card-tag {
  font-size: 0.82rem;
}

.article-date {
  font-size: 0.82rem;
  color: var(--text-muted);
}

.article-title {
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1.3;
  margin-bottom: 16px;
}

.article-subtitle {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.article-content h2 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
  margin: 40px 0 16px;
  padding-top: 8px;
}

.article-content h3 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-primary-light);
  margin: 28px 0 12px;
}

.article-content p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  line-height: 1.8;
}

.article-content ul,
.article-content ol {
  margin: 16px 0 16px 24px;
  color: var(--text-secondary);
}

.article-content li {
  margin-bottom: 8px;
  line-height: 1.7;
}

.article-content strong {
  color: var(--text-primary);
}

.article-content code {
  font-family: var(--font-mono);
  background: var(--bg-code);
  color: var(--color-secondary);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.875em;
}

.article-content pre {
  background: var(--bg-code);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 20px 24px;
  margin: 20px 0;
  overflow-x: auto;
  position: relative;
}

.article-content pre code {
  background: none;
  padding: 0;
  color: #e2e8f0;
  font-size: 0.875rem;
  line-height: 1.7;
}

.article-content .pre-label {
  position: absolute;
  top: 8px;
  right: 12px;
  font-size: 0.7rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.article-content blockquote {
  border-left: 3px solid var(--color-primary);
  background: rgba(59, 130, 246, 0.05);
  padding: 16px 20px;
  margin: 20px 0;
  border-radius: 0 var(--radius) var(--radius) 0;
}

.article-content blockquote p {
  margin: 0;
  color: var(--text-primary);
}

.tip-box {
  background: rgba(6, 182, 212, 0.08);
  border: 1px solid rgba(6, 182, 212, 0.2);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  margin: 20px 0;
}

.tip-box .tip-label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--color-secondary);
  margin-bottom: 8px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.tip-box p {
  margin: 0;
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 0.875rem;
}

.comparison-table th {
  background: var(--bg-code);
  color: var(--text-primary);
  padding: 12px 16px;
  text-align: left;
  border: 1px solid var(--border-color);
  font-weight: 600;
}

.comparison-table td {
  padding: 10px 16px;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  vertical-align: top;
}

.comparison-table tr:nth-child(even) td {
  background: rgba(255,255,255,0.02);
}

/* ===== Article Nav ===== */
.article-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 60px;
  padding-top: 32px;
  border-top: 1px solid var(--border-color);
}

.article-nav-btn {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  text-decoration: none;
  color: var(--text-secondary);
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.article-nav-btn:hover {
  border-color: var(--color-primary);
  color: var(--text-primary);
  background: var(--bg-card-hover);
}

.article-nav-btn .nav-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.article-nav-btn .nav-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-primary-light);
}

.article-nav-btn.prev { text-align: left; }
.article-nav-btn.next { text-align: right; }
.article-nav-btn.next-only {
  grid-column: 2;
}

/* ===== Back Button ===== */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-muted);
  font-size: 0.875rem;
  padding: 8px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  cursor: pointer;
  transition: all var(--transition);
  margin-bottom: 32px;
  text-decoration: none;
}

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

/* ===== Responsive ===== */
@media (max-width: 900px) {
  .article-layout {
    grid-template-columns: 1fr;
  }
  .toc-sidebar {
    display: none;
  }
  .about-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .nav-links { display: none; }
  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    padding: 16px;
    gap: 4px;
  }
  .nav-menu-btn { display: block; }
  .hero-stats { gap: 24px; }
  .articles-grid { grid-template-columns: 1fr; }
  .article-nav { grid-template-columns: 1fr; }
  .article-nav-btn.next-only { grid-column: 1; }
}