:root {
  --bg: #ffffff;
  --header-bg: rgba(255, 255, 255, 0.95);
  --text: #212529;
  --muted: #6c757d;
  --link: #2761e3;
  --border: #e9ecef;
  --sep: #ced4da;
  --pill-bg: #f1f3f5;
  --code-bg: #f6f8fa;
  --max-width: 1080px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1117;
    --header-bg: rgba(13, 17, 23, 0.95);
    --text: #e6edf3;
    --muted: #9198a1;
    --link: #6ea8fe;
    --border: #2d333b;
    --sep: #444c56;
    --pill-bg: #21262d;
    --code-bg: #161b22;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 17px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}

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

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--header-bg);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--border);
}

.site-nav {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.7rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-brand {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--text);
}
.site-brand:hover { text-decoration: none; color: var(--link); }

.site-links {
  display: flex;
  align-items: center;
  gap: 1.1rem;
}
.site-links a {
  color: var(--text);
  font-size: 0.95rem;
}
.site-links > a:not(.icon-link) {
  text-transform: uppercase;
  font-size: 0.82rem;
  letter-spacing: 0.06em;
}
.site-links a:hover { color: var(--link); text-decoration: none; }
.icon-link { display: inline-flex; align-items: center; }

/* ---------- layout ---------- */
.site-main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.25rem 3rem;
}

.home-columns {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 200px;
  gap: 3rem;
}

.home-intro {
  color: var(--muted);
  font-size: 0.98rem;
  margin-bottom: 1.5rem;
}
.home-intro h2 { color: var(--text); font-size: 1.15rem; margin-bottom: 0; }

/* ---------- post list ---------- */
.post-item {
  display: flex;
  gap: 1.5rem;
  padding: 1.4rem 0;
  border-bottom: 1px solid var(--border);
}
.post-item:last-child { border-bottom: none; }

.post-item-body { flex: 1; min-width: 0; }

.post-item-title {
  margin: 0 0 0.35rem;
  font-size: 1.35rem;
  line-height: 1.3;
  font-weight: 600;
}
.post-item-title a { color: var(--text); }
.post-item-title a:hover { color: var(--link); text-decoration: none; }

.post-item-desc {
  margin: 0 0 0.6rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.post-item-meta, .post-meta {
  color: var(--muted);
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.45rem;
}
.meta-sep { color: var(--sep); }

.tag {
  display: inline-block;
  background: var(--pill-bg);
  border-radius: 0.25rem;
  padding: 0.1rem 0.5rem;
  font-size: 0.78rem;
  color: var(--muted);
}

.post-item-thumb img {
  width: 160px;
  height: 110px;
  object-fit: cover;
  border-radius: 0.4rem;
}

/* ---------- sidebar ---------- */
.sidebar-title {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.6rem;
}

.category-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.category-list li { margin: 0.3rem 0; }
.category-link {
  color: var(--muted);
  font-size: 0.9rem;
}
.category-link.active { color: var(--link); font-weight: 600; }

/* ---------- post page ---------- */
.post { max-width: 760px; margin: 0 auto; }

.post-title {
  font-size: 2rem;
  line-height: 1.25;
  margin: 0.5rem 0 0.6rem;
  font-weight: 700;
}

.post-header { margin-bottom: 2rem; }

.post-content h2 { margin-top: 2.2rem; font-size: 1.45rem; }
.post-content h3 { margin-top: 1.8rem; font-size: 1.15rem; }

.post-content blockquote {
  margin: 1.5rem 0;
  padding: 0.2rem 0 0.2rem 1.1rem;
  border-left: 3px solid var(--link);
  color: var(--muted);
  font-size: 1.05rem;
}
.post-content blockquote p { margin: 0.4rem 0; }

.post-content img, .post-content svg { max-width: 100%; }

.post-content table {
  border-collapse: collapse;
  display: block;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-size: 0.9rem;
}
.post-content th, .post-content td {
  border: 1px solid var(--border);
  padding: 0.45rem 0.7rem;
  text-align: left;
}
.post-content th { background: var(--pill-bg); }

.post-content code {
  background: var(--code-bg);
  border-radius: 0.25rem;
  padding: 0.1rem 0.35rem;
  font-size: 0.85em;
}
.post-content pre {
  background: var(--code-bg);
  border-radius: 0.4rem;
  padding: 0.9rem 1.1rem;
  overflow-x: auto;
}
.post-content pre code { background: none; padding: 0; }

pre.mermaid {
  background: none;
  border: none;
  text-align: center;
  margin: 1.8rem 0;
}

.post-footer {
  margin-top: 3rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--border);
  font-size: 0.95rem;
}

/* ---------- footer ---------- */
.site-footer {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 1.2rem 1.25rem 2rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
  display: flex;
  justify-content: space-between;
}
.footer-links { display: flex; gap: 1rem; }
.footer-links a { color: var(--muted); }

/* ---------- responsive ---------- */
@media (max-width: 768px) {
  .home-columns { grid-template-columns: 1fr; gap: 1.5rem; }
  .home-sidebar { order: -1; }
  .category-list { display: flex; flex-wrap: wrap; gap: 0.2rem 0.9rem; }
  .post-item-thumb { display: none; }
  .post-title { font-size: 1.6rem; }
}