:root {
  --color-bg: #f8f9fa;
  --color-surface: #ffffff;
  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-primary-light: #eff6ff;
  --color-text: #1f2937;
  --color-text-secondary: #6b7280;
  --color-border: #d1d5db;
  --color-success: #16a34a;
  --color-success-bg: #f0fdf4;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  font-size: 16px;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Nav */
.seo-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  flex-wrap: wrap;
  gap: 0.5rem;
}
.seo-nav-brand {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-text);
}
.seo-nav-links { display: flex; gap: 1.5rem; }
.seo-nav-links a { color: var(--color-text-secondary); font-size: 0.9rem; }
.seo-nav-links a:hover { color: var(--color-primary); }

/* Breadcrumbs */
.breadcrumbs {
  padding: 0.75rem 2rem;
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}
.breadcrumbs ol {
  display: flex;
  list-style: none;
  gap: 0.5rem;
  flex-wrap: wrap;
}
.breadcrumbs li:not(:last-child)::after {
  content: '/';
  margin-left: 0.5rem;
  color: var(--color-border);
}
.breadcrumbs a { color: var(--color-text-secondary); }
.breadcrumbs [aria-current="page"] a {
  color: var(--color-text);
  font-weight: 500;
}

/* Main content */
.seo-main {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem;
}
.seo-main h1 {
  font-size: 1.75rem;
  line-height: 1.3;
  margin-bottom: 1.5rem;
  color: var(--color-text);
}
.seo-main h2 {
  font-size: 1.3rem;
  margin-top: 2rem;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}
.seo-main h3 {
  font-size: 1.1rem;
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
}
.seo-main p {
  margin-bottom: 1rem;
  color: var(--color-text-secondary);
}

/* Dimension highlight card */
.dim-card {
  background: var(--color-primary-light);
  border: 1px solid var(--color-primary);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 2rem;
}
.dim-card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
}
.dim-item { text-align: center; }
.dim-label {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-secondary);
  margin-bottom: 0.25rem;
}
.dim-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  font-variant-numeric: tabular-nums;
}
.dim-sub {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

/* Tables */
.dim-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 2rem;
  font-size: 0.95rem;
}
.dim-table th, .dim-table td {
  padding: 0.65rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}
.dim-table th {
  font-weight: 600;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--color-text-secondary);
  background: var(--color-bg);
}
.dim-table td { font-variant-numeric: tabular-nums; }
.dim-table tr:hover td { background: var(--color-primary-light); }
.dim-table .highlight td {
  background: var(--color-success-bg);
  font-weight: 600;
}

/* Formula block */
.formula-block {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin: 1rem 0 1.5rem;
  font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
  font-size: 0.9rem;
  line-height: 1.8;
  overflow-x: auto;
}

/* Info box */
.info-box {
  background: var(--color-primary-light);
  border-left: 3px solid var(--color-primary);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 1rem 0;
  font-size: 0.95rem;
}

/* Spec list */
.spec-list {
  list-style: none;
  margin: 0.5rem 0 1.5rem;
}
.spec-list li {
  padding: 0.4rem 0;
  padding-left: 1.5rem;
  position: relative;
  color: var(--color-text-secondary);
}
.spec-list li::before {
  content: '\2713';
  position: absolute;
  left: 0;
  color: var(--color-success);
  font-weight: 700;
}

/* Related links */
.related-links {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 0.75rem;
  margin: 1rem 0 2rem;
}
.related-link {
  display: block;
  padding: 0.75rem 1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 0.9rem;
  transition: border-color 0.15s;
}
.related-link:hover {
  border-color: var(--color-primary);
  text-decoration: none;
}

/* Hub page cards */
.hub-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
  margin: 1rem 0;
}
.hub-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem;
}
.hub-card h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1rem;
}
.hub-card p {
  font-size: 0.9rem;
  margin-bottom: 0.75rem;
}
.hub-card-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}
.hub-card-links a {
  font-size: 0.85rem;
  padding: 0.25rem 0.5rem;
  background: var(--color-bg);
  border-radius: 4px;
}

/* CTA */
.seo-cta {
  text-align: center;
  padding: 3rem 2rem;
  background: var(--color-primary-light);
  margin-top: 3rem;
}
.seo-cta h2 {
  font-size: 1.5rem;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}
.seo-cta p {
  color: var(--color-text-secondary);
  margin-bottom: 1.5rem;
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
}
.btn-primary {
  display: inline-block;
  padding: 0.75rem 2rem;
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 1rem;
  transition: background 0.15s;
}
.btn-primary:hover {
  background: var(--color-primary-hover);
  text-decoration: none;
}

/* Footer */
.seo-footer {
  text-align: center;
  padding: 2rem;
  border-top: 1px solid var(--color-border);
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}
.seo-footer nav {
  margin-top: 0.5rem;
}
.seo-footer nav a {
  color: var(--color-text-secondary);
  margin: 0 0.5rem;
}

/* FAQ */
.faq-answer {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin: 1rem 0 2rem;
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--color-text);
}

/* ── Blog ── */
.blog-header { margin-bottom: 2rem; }

.blog-meta {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--color-muted);
  font-size: 0.9rem;
  margin-top: 0.5rem;
  flex-wrap: wrap;
}

.blog-meta-sep { color: var(--color-muted); }

.blog-category {
  background: var(--color-primary);
  color: #fff;
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
  font-size: 0.8rem;
  font-weight: 500;
}

.blog-content {
  line-height: 1.8;
  font-size: 1.05rem;
}

.blog-content h2 {
  margin-top: 2rem;
  margin-bottom: 0.75rem;
}

.blog-content h3 {
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
}

.blog-content p { margin-bottom: 1rem; }

.blog-content ul, .blog-content ol {
  margin-bottom: 1rem;
  padding-left: 1.5rem;
}

.blog-content li { margin-bottom: 0.4rem; }

.blog-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.95rem;
}

.blog-content table th,
.blog-content table td {
  border: 1px solid var(--color-border);
  padding: 0.6rem 0.8rem;
  text-align: left;
}

.blog-content table th {
  background: var(--color-surface);
  font-weight: 600;
}

.blog-content table tr:hover td {
  background: var(--color-surface);
}

.blog-content .callout {
  border-left: 4px solid var(--color-primary);
  background: var(--color-surface);
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  border-radius: 0 var(--radius) var(--radius) 0;
}

.blog-content .callout--warning {
  border-left-color: #e67e22;
}

.blog-content .callout--tip {
  border-left-color: #27ae60;
}

.blog-footer { margin-top: 2rem; }

.blog-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.blog-tag {
  background: var(--color-surface);
  color: var(--color-muted);
  padding: 0.25rem 0.75rem;
  border-radius: 999px;
  font-size: 0.8rem;
  border: 1px solid var(--color-border);
}

.blog-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin: 1.5rem 0;
}

.blog-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: box-shadow 0.2s;
}

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

.blog-card h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
}

.blog-card h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.blog-card h3 a:hover {
  color: var(--color-primary);
}

.blog-card-meta {
  font-size: 0.8rem;
  color: var(--color-muted);
  margin-bottom: 0.5rem;
}

.blog-card p {
  font-size: 0.9rem;
  color: var(--color-muted);
  margin: 0;
  line-height: 1.5;
}

/* Responsive */
@media (max-width: 768px) {
  .seo-nav { padding: 0.75rem 1rem; }
  .seo-nav-links { gap: 1rem; }
  .breadcrumbs { padding: 0.5rem 1rem; }
  .seo-main { padding: 1.5rem 1rem; }
  .seo-main h1 { font-size: 1.4rem; }
  .dim-card-grid { grid-template-columns: repeat(2, 1fr); }
  .dim-value { font-size: 1.2rem; }
  .dim-table { font-size: 0.85rem; }
  .dim-table th, .dim-table td { padding: 0.5rem 0.5rem; }
  .related-links { grid-template-columns: 1fr; }
  .hub-grid { grid-template-columns: 1fr; }
  .blog-grid { grid-template-columns: 1fr; }
  .blog-content { font-size: 1rem; }
}