:root {
  --bg: #fbfaf7;
  --bg-elev: #ffffff;
  --text: #1f2328;
  --text-dim: #5b6169;
  --accent: #8a3b2e;
  --accent-soft: #f4e7e2;
  --border: #e7e2da;
  --code-bg: #f1efe9;
  --max-width: 780px;
  --serif: "Noto Serif SC", "Songti SC", "STSong", Georgia, "Times New Roman", serif;
  --sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", -apple-system, BlinkMacSystemFont, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #16181b;
    --bg-elev: #1d2024;
    --text: #e8e6e1;
    --text-dim: #9a9d9f;
    --accent: #e29a86;
    --accent-soft: #2b2320;
    --border: #2c2f33;
    --code-bg: #232629;
  }
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--serif);
  line-height: 1.75;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
}

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

.site-header {
  border-bottom: 1px solid var(--border);
  padding: 18px 20px;
  position: sticky;
  top: 0;
  background: rgba(251, 250, 247, 0.92);
  backdrop-filter: blur(6px);
  z-index: 10;
}
@media (prefers-color-scheme: dark) {
  .site-header { background: rgba(22, 24, 27, 0.92); }
}

.site-header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
}

.site-title {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  letter-spacing: 0.02em;
}
.site-title:hover { text-decoration: none; opacity: 0.8; }

.site-tagline {
  font-family: var(--sans);
  font-size: 0.8rem;
  color: var(--text-dim);
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 20px 80px;
}

/* ---------- index / post list ---------- */

.category-group { margin-bottom: 40px; }

.category-title {
  font-family: var(--sans);
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin: 0 0 14px;
}

.post-card {
  display: block;
  padding: 18px 20px;
  margin-bottom: 12px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 10px;
  transition: border-color 0.15s ease;
}
.post-card:hover {
  text-decoration: none;
  border-color: var(--accent);
}

.post-card-title {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  margin: 0 0 6px;
}

.post-card-summary {
  font-family: var(--sans);
  font-size: 0.88rem;
  color: var(--text-dim);
  line-height: 1.6;
  margin: 0;
}

.empty-note {
  font-family: var(--sans);
  color: var(--text-dim);
  font-size: 0.9rem;
  padding: 24px 0;
}

/* ---------- post page ---------- */

.post-header { margin-bottom: 28px; }

.post-category {
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.post-title {
  font-size: 1.7rem;
  line-height: 1.35;
  margin: 8px 0 0;
}

.toc-block {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 4px 18px;
  margin-bottom: 32px;
  font-family: var(--sans);
}
.toc-block summary {
  cursor: pointer;
  padding: 12px 0;
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--text);
}
.toc-list {
  list-style: none;
  margin: 0;
  padding: 0 0 14px;
}
.toc-list li { margin: 6px 0; }
.toc-list a {
  font-size: 0.88rem;
  color: var(--text-dim);
}
.toc-list a:hover { color: var(--accent); }
.toc-list .toc-h3 { padding-left: 16px; }

.post-content { overflow-wrap: break-word; }

.post-content h1,
.post-content h2,
.post-content h3,
.post-content h4 {
  font-family: var(--sans);
  line-height: 1.4;
  scroll-margin-top: 70px;
}
.post-content h2 {
  font-size: 1.3rem;
  margin-top: 2.4em;
  padding-bottom: 0.4em;
  border-bottom: 1px solid var(--border);
}
.post-content h3 { font-size: 1.1rem; margin-top: 1.8em; }
.post-content h4 { font-size: 1rem; margin-top: 1.5em; }

.post-content p { margin: 1em 0; }

.post-content blockquote {
  margin: 1.4em 0;
  padding: 0.2em 1.1em;
  border-left: 3px solid var(--border);
  color: var(--text-dim);
  font-size: 0.96rem;
}

.post-content .callout {
  margin: 1.4em 0;
  padding: 14px 18px;
  border-radius: 8px;
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  color: var(--text);
  font-size: 0.96rem;
}
.post-content .callout-title {
  font-family: var(--sans);
  font-weight: 700;
  margin-bottom: 6px;
  color: var(--accent);
}
.post-content .callout p:first-child { margin-top: 0; }
.post-content .callout p:last-child { margin-bottom: 0; }

.post-content table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.6em 0;
  font-size: 0.9rem;
  display: block;
  overflow-x: auto;
}
.post-content th, .post-content td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}
.post-content th {
  font-family: var(--sans);
  background: var(--code-bg);
}

.post-content code {
  font-family: "SF Mono", Consolas, Menlo, monospace;
  background: var(--code-bg);
  padding: 0.1em 0.35em;
  border-radius: 4px;
  font-size: 0.88em;
}

.post-content hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 2.4em 0;
}

.post-content .katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 4px 0;
}

.post-content ul, .post-content ol {
  padding-left: 1.4em;
}
.post-content li { margin: 0.4em 0; }

.post-footer {
  margin-top: 60px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  font-family: var(--sans);
  font-size: 0.85rem;
  color: var(--text-dim);
}

.loading, .error-box {
  font-family: var(--sans);
  color: var(--text-dim);
  padding: 40px 0;
}
.error-box { color: var(--accent); }

@media (max-width: 600px) {
  body { font-size: 16.5px; }
  main { padding: 24px 16px 60px; }
  .post-title { font-size: 1.4rem; }
}