/* Deep Research Blog — Polished Dark Theme */
:root {
  --bg: #0a0a0f;
  --surface: #13131a;
  --surface-hover: #1a1a24;
  --border: #23232e;
  --border-hover: #3a3a4a;
  --text: #ededf0;
  --text-secondary: #9494a0;
  --text-muted: #6b6b78;
  --accent: #6e8eff;
  --accent-soft: #6e8eff18;
  --accent-hover: #8fa8ff;
  --num-bg: #1e1e2a;
  --tag-bg: #1e1e2a;
  --tag-text: #8888a0;
  --radius: 12px;
  --radius-sm: 8px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.8;
  font-size: 16.5px;
  -webkit-font-smoothing: antialiased;
}

.wrapper {
  max-width: 740px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Header */
.site-header {
  padding: 24px 0;
  border-bottom: 1px solid var(--border);
}
.site-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.site-title:hover { color: var(--text); }

/* Hero */
.hero {
  padding: 56px 0 40px;
  text-align: center;
}
.hero h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 12px;
}
.hero-desc {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.7;
}

/* Series Section */
.series-section {
  padding-bottom: 60px;
}
.series-heading {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 4px;
  letter-spacing: -0.01em;
}
.series-desc {
  color: var(--text-muted);
  font-size: 0.88rem;
  margin-bottom: 24px;
}

/* Article Cards */
.article-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.article-card {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 18px;
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: var(--text);
  transition: background 0.15s ease, transform 0.1s ease;
  border: 1px solid transparent;
}
.article-card:hover {
  background: var(--surface-hover);
  border-color: var(--border);
}
.article-card:active {
  transform: scale(0.995);
}

.article-num {
  flex-shrink: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--num-bg);
  border-radius: 8px;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
}

.article-info {
  flex: 1;
  min-width: 0;
}

.article-title {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 4px;
  line-height: 1.4;
}
.article-card:hover .article-title {
  color: var(--accent-hover);
}

.article-summary {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 6px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.article-meta {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}
.article-tag {
  font-size: 0.72rem;
  color: var(--tag-text);
  background: var(--tag-bg);
  padding: 2px 8px;
  border-radius: 4px;
}

.article-arrow {
  flex-shrink: 0;
  color: var(--text-muted);
  font-size: 1.1rem;
  opacity: 0;
  transition: opacity 0.15s, transform 0.15s;
}
.article-card:hover .article-arrow {
  opacity: 1;
  transform: translateX(2px);
}

/* Post Page */
.post-header {
  margin-bottom: 48px;
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--border);
}
.series-nav-top {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-bottom: 16px;
}
.series-nav-top a {
  color: var(--accent);
  text-decoration: none;
}
.series-nav-top a:hover { text-decoration: underline; }
.series-progress { color: var(--text-muted); }

.post-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.3;
  margin-bottom: 16px;
}
.post-meta {
  color: var(--text-muted);
  font-size: 0.85rem;
}
.post-meta span { margin-right: 14px; }
.post-tags { margin-top: 12px; }
.tag {
  display: inline-block;
  background: var(--tag-bg);
  color: var(--tag-text);
  padding: 3px 10px;
  border-radius: 5px;
  font-size: 0.78rem;
  margin-right: 6px;
}

/* Post Content */
.post-content {
  padding-bottom: 48px;
}
.post-content h2 {
  font-size: 1.3rem;
  font-weight: 650;
  margin: 48px 0 16px;
  letter-spacing: -0.01em;
  color: var(--text);
}
.post-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 32px 0 10px;
  color: var(--text);
}
.post-content p {
  margin-bottom: 18px;
  color: var(--text-secondary);
}
.post-content strong {
  color: var(--text);
  font-weight: 600;
}
.post-content a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid var(--accent-soft);
}
.post-content a:hover {
  border-bottom-color: var(--accent);
}
.post-content code {
  background: var(--surface);
  padding: 2px 7px;
  border-radius: 5px;
  font-size: 0.88em;
  font-family: 'SF Mono', 'Fira Code', monospace;
}
.post-content pre {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 18px 20px;
  overflow-x: auto;
  margin: 20px 0;
  font-size: 0.88em;
  line-height: 1.6;
}
.post-content pre code {
  background: none;
  padding: 0;
}
.post-content blockquote {
  border-left: 3px solid var(--border-hover);
  padding: 12px 0 12px 20px;
  margin: 24px 0;
  color: var(--text-secondary);
  font-style: italic;
}
.post-content ul, .post-content ol {
  margin: 10px 0 20px 24px;
  color: var(--text-secondary);
}
.post-content li { margin-bottom: 8px; }
.post-content img {
  max-width: 100%;
  border-radius: var(--radius-sm);
  margin: 24px 0;
}
.post-content hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 48px 0;
}
.post-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 0.9em;
}
.post-content th, .post-content td {
  border: 1px solid var(--border);
  padding: 10px 14px;
  text-align: left;
}
.post-content th {
  background: var(--surface);
  font-weight: 600;
  color: var(--text);
}
.post-content td { color: var(--text-secondary); }

/* Series bottom navigation */
.series-nav-bottom {
  display: flex;
  justify-content: space-between;
  margin-top: 48px;
  padding: 24px 0;
  border-top: 1px solid var(--border);
  gap: 24px;
}
.series-nav-bottom a {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.15s;
}
.series-nav-bottom a:hover { color: var(--accent-hover); }
.nav-prev, .nav-next { max-width: 48%; }
.nav-next { text-align: right; }

/* Footer */
.site-footer {
  padding: 24px 0;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.82rem;
}
.site-footer a {
  color: var(--text-secondary);
  text-decoration: none;
}
.site-footer a:hover { color: var(--text); }

/* Responsive */
@media (max-width: 600px) {
  .wrapper { padding: 0 16px; }
  body { font-size: 15.5px; }
  .hero { padding: 40px 0 28px; }
  .hero h1 { font-size: 1.6rem; }
  .post-title { font-size: 1.4rem; }
  .article-card { padding: 14px 12px; }
  .article-summary { display: none; }
  .series-nav-bottom { flex-direction: column; gap: 12px; }
  .nav-prev, .nav-next { max-width: 100%; text-align: left; }
}