/* ============================================================
   ReLU.chat — Blog stylesheet
   v5 tokens from shared-design.css. Low color variance.
   ============================================================ */

nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  padding: 0 var(--space-6);
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 600;
  font-size: 0.9375rem;
}
.nav-logo img { width: 24px; height: 24px; }
.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  list-style: none;
}
.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.15s ease;
}
.nav-links a:hover { color: var(--text-primary); }
.nav-links a.active { color: var(--text-primary); }
.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius);
  background: transparent;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.8125rem;
  font-weight: 500;
  border: 1px solid var(--accent);
  transition: border-color 0.15s ease, background 0.15s ease, color 0.15s ease;
}
.nav-cta:hover { background: rgba(20, 184, 166, 0.10); color: var(--accent); }

.blog-container {
  max-width: 940px;
  margin: 0 auto;
  padding: var(--space-16) var(--space-6) var(--space-20);
}

.blog-hero {
  margin-bottom: var(--space-10);
}
.blog-hero-top {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: var(--space-6);
  flex-wrap: wrap;
}
.blog-hero h1 {
  font-size: clamp(1.75rem, 5vw, 2.75rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: var(--space-2);
}
.blog-hero-sub {
  color: var(--text-secondary);
  font-size: 1rem;
  max-width: 560px;
  line-height: 1.6;
}
.blog-hero-accent {
  width: 48px;
  height: 2px;
  background: var(--border-strong);
  margin: var(--space-3) 0 0;
}
.blog-hero-stats {
  display: flex;
  gap: var(--space-4);
  margin-top: var(--space-3);
}
.blog-hero-stat {
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.02em;
}
.blog-hero-stat strong {
  color: var(--text-secondary);
  font-weight: 600;
}

.featured-card {
  display: block;
  text-decoration: none;
  margin-bottom: var(--space-10);
  position: relative;
}
.featured-card-inner {
  display: grid;
  grid-template-columns: 1fr 280px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-elevated);
  transition: border-color 0.15s ease;
}
.featured-card:hover .featured-card-inner { border-color: var(--border-strong); }
.featured-card-content {
  padding: var(--space-7);
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.featured-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: var(--space-3);
  background: var(--bg-surface);
  padding: 2px var(--space-2);
  border-radius: var(--radius);
  width: fit-content;
  border: 1px solid var(--border);
}
.featured-tags {
  display: flex;
  gap: 6px;
  margin-bottom: var(--space-3);
}
.featured-title {
  font-size: clamp(1.375rem, 3vw, 1.75rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: var(--space-3);
  color: var(--text-primary);
}
.featured-excerpt {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--space-3);
  max-width: 480px;
}
.featured-meta {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: var(--space-3);
}
.featured-dot {
  width: 3px;
  height: 3px;
  border-radius: 50%;
  background: var(--text-muted);
  opacity: 0.5;
}
.featured-cta {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-primary);
  transition: color 0.15s ease;
}
.featured-card:hover .featured-cta { color: var(--accent); }
.featured-arrow { transition: transform 0.15s ease; }
.featured-card:hover .featured-arrow { transform: translateX(2px); }

.featured-visual {
  position: relative;
  overflow: hidden;
  background: var(--bg-surface);
  border-left: 1px solid var(--border);
}
.featured-cover-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: grayscale(100%) contrast(0.95) brightness(0.95);
  transition: filter 0.15s ease;
}
.featured-card:hover .featured-cover-img { filter: grayscale(100%) contrast(1) brightness(1); }

.filter-bar {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-10);
  flex-wrap: wrap;
  align-items: center;
}
.filter-label {
  font-size: 0.6875rem;
  color: var(--text-muted);
  font-weight: 500;
  margin-right: 4px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.filter-pill {
  display: inline-flex;
  align-items: center;
  padding: 4px var(--space-3);
  border-radius: var(--radius);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.75rem;
  font-weight: 500;
  cursor: pointer;
  transition: border-color 0.15s ease, color 0.15s ease, background 0.15s ease;
  font-family: var(--font);
}
.filter-pill:hover {
  border-color: var(--border-strong);
  color: var(--text-primary);
}
.filter-pill.active {
  background: var(--bg-surface);
  border-color: var(--accent);
  color: var(--accent);
}

.blog-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-5);
}

.blog-card {
  position: relative;
  display: flex;
  flex-direction: column;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  text-decoration: none;
  transition: border-color 0.15s ease;
  animation: cardIn 0.4s ease both;
  animation-delay: calc(var(--card-idx, 0) * 0.05s);
}
.blog-card:hover { border-color: var(--border-strong); }

.blog-card-accent {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--border);
  opacity: 0;
  transition: opacity 0.15s ease, background 0.15s ease;
}
.blog-card:hover .blog-card-accent { opacity: 1; background: var(--accent); }

.blog-card-img {
  width: 100%;
  height: 160px;
  overflow: hidden;
  position: relative;
  background: var(--bg-surface);
}
.blog-card-img img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: grayscale(100%) contrast(0.95) brightness(0.95);
  transition: filter 0.15s ease;
}
.blog-card:hover .blog-card-img img { filter: grayscale(100%) contrast(1) brightness(1); }

.blog-card-body {
  padding: var(--space-5);
  flex: 1;
  display: flex;
  flex-direction: column;
}
.blog-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-2);
}
.blog-card-tags {
  display: flex;
  gap: 4px;
}
.article-tag {
  font-size: 0.6875rem;
  padding: 2px 6px;
  background: var(--bg-surface);
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-weight: 500;
}
.blog-card-read {
  font-size: 0.6875rem;
  color: var(--text-muted);
  font-weight: 500;
}
.blog-card-title {
  font-size: 1rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-primary);
  margin-bottom: var(--space-2);
  line-height: 1.35;
}
.blog-card-excerpt {
  font-size: 0.8125rem;
  color: var(--text-secondary);
  line-height: 1.6;
  flex: 1;
  margin-bottom: var(--space-3);
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.blog-card-meta {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  color: var(--text-muted);
}
.blog-card-meta .dot {
  width: 3px;
  height: 3px;
  border-radius: 50%;
  background: var(--text-muted);
  opacity: 0.5;
}

.blog-empty {
  text-align: center;
  padding: var(--space-16) var(--space-6);
  color: var(--text-muted);
}
.blog-empty h2 {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-2);
}

footer {
  border-top: 1px solid var(--border);
  padding: var(--space-6);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.8125rem;
}
footer p { margin-bottom: var(--space-1); font-size: 0.8125rem; }
footer a { color: var(--text-secondary); text-decoration: underline; }
footer a:hover { color: var(--accent); }

@keyframes cardIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

@media (max-width: 640px) {
  .blog-container { padding: var(--space-10) var(--space-4) var(--space-12); }
  .article-container { padding: var(--space-10) var(--space-4) var(--space-12); }
  .blog-grid { grid-template-columns: 1fr; }
  .featured-card-inner { grid-template-columns: 1fr; }
  .featured-visual { height: 160px; border-left: none; border-top: 1px solid var(--border); }
  .featured-card-content { padding: var(--space-5) var(--space-4); }
  .blog-hero-top { flex-direction: column; align-items: flex-start; }
  .article-body h2 { margin: var(--space-10) 0 var(--space-3); }
  .nav-cta span.nav-label { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .blog-card { animation: none; }
}

/* ============================================================
   Blog post (article) styles
   ============================================================ */

.article-container {
  max-width: 760px;
  margin: 0 auto;
  padding: var(--space-16) var(--space-6) var(--space-20);
}

.article-breadcrumb {
  font-size: 0.8125rem;
  color: var(--text-muted);
  margin-bottom: var(--space-6);
}
.article-breadcrumb a {
  color: var(--text-secondary);
  text-decoration: none;
}
.article-breadcrumb a:hover { color: var(--text-primary); }
.article-breadcrumb .sep { margin: 0 var(--space-2); opacity: 0.4; }

.article-hero-title {
  font-size: clamp(1.75rem, 5.5vw, 2.625rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: 0;
}

.article-meta-bar {
  display: flex;
  align-items: center;
  margin: var(--space-3) 0 var(--space-6);
  padding: var(--space-3) 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}
.article-meta-item {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  padding: 0 var(--space-4);
  border-right: 1px solid var(--border);
}
.article-meta-item:first-child { padding-left: 0; }
.article-meta-item:last-child { border-right: none; }
.article-meta-item svg { width: 14px; height: 14px; opacity: 0.5; flex-shrink: 0; }

.article-divider {
  width: 48px;
  height: 2px;
  background: var(--border-strong);
  margin: 0 0 var(--space-8);
}

.article-tags {
  display: flex;
  gap: var(--space-1);
  flex-wrap: wrap;
  margin-bottom: var(--space-6);
}

.article-cover {
  width: 100%;
  max-height: 420px;
  object-fit: cover;
  border-radius: var(--radius);
  margin-bottom: var(--space-10);
  border: 1px solid var(--border);
}

.article-body { font-size: 0.9375rem; line-height: 1.75; }
.article-body h2 {
  font-size: 1.375rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  margin: var(--space-14) 0 var(--space-4);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--border);
  color: var(--text-primary);
}
.article-body h3 {
  font-size: 1.0625rem;
  font-weight: 600;
  margin: var(--space-6) 0 var(--space-2);
  color: var(--text-primary);
}
.article-body h4 {
  font-size: 0.9375rem;
  font-weight: 600;
  margin: var(--space-6) 0 var(--space-2);
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.article-body p {
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  font-size: 0.9375rem;
}
.article-body a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: var(--border-strong);
  transition: text-decoration-color 0.15s ease;
}
.article-body a:hover { text-decoration-color: var(--accent); }
.article-body strong { color: var(--text-primary); font-weight: 600; }
.article-body em { font-style: italic; }
.article-body ul, .article-body ol {
  color: var(--text-secondary);
  padding-left: var(--space-5);
  margin-bottom: var(--space-4);
}
.article-body li { margin-bottom: 6px; }
.article-body li::marker { color: var(--text-muted); }
.article-body pre {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-4) var(--space-5);
  overflow-x: auto;
  margin-bottom: var(--space-5);
  font-size: 0.8125rem;
  line-height: 1.6;
}
.article-body pre code {
  background: transparent;
  color: var(--text-secondary);
  padding: 0;
  font-size: 0.8125rem;
  border: none;
}
.article-body img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin: var(--space-5) 0;
  border: 1px solid var(--border);
}
.article-body blockquote {
  border-left: 2px solid var(--border-strong);
  background: var(--bg-elevated);
  padding: var(--space-3) var(--space-4);
  margin: var(--space-5) 0;
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--text-secondary);
}
.article-body blockquote p:last-child { margin-bottom: 0; }
.article-body hr {
  border: none;
  height: 1px;
  background: var(--border);
  margin: var(--space-10) 0;
}
.article-body .drop-cap::first-letter {
  float: left;
  font-size: 2.5em;
  line-height: 0.9;
  padding-right: var(--space-2);
  padding-top: 2px;
  color: var(--text-primary);
  font-weight: 600;
}

.article-footer {
  margin-top: var(--space-14);
  padding-top: var(--space-8);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-4);
}
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 500;
  transition: color 0.15s ease;
}
.back-link:hover { color: var(--accent); }

.share-links { display: flex; gap: var(--space-2); }
.share-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: var(--radius);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.8125rem;
  transition: border-color 0.15s ease, color 0.15s ease;
}
.share-link:hover { border-color: var(--border-strong); color: var(--text-primary); }

@media (max-width: 640px) {
  .article-container { padding: var(--space-6) var(--space-4) var(--space-12); }
  .article-meta-bar { flex-wrap: wrap; gap: var(--space-2); padding: var(--space-3) 0; }
  .article-meta-item { border-right: none; padding: 0 var(--space-3) 0 0; }
  .article-footer { flex-direction: column; align-items: flex-start; }
}