:root {
  --paper: #faf9f6;
  --ink: #30332e;
  --muted: #85877f;
  --line: #e6e6df;
  --accent: #65745c;
  --serif: Georgia, 'Songti SC', serif;
  --sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', sans-serif;
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 15px/1.85 var(--sans); }
a { color: inherit; text-decoration: none; }
a:hover { color: var(--accent); }
a:focus-visible { outline: 1px solid var(--accent); outline-offset: 6px; }
::selection { background: #e1e6d9; }
.wrap { max-width: 860px; min-height: 100svh; margin: auto; padding: 0 48px; display: flex; flex-direction: column; }
.header { display: flex; align-items: center; justify-content: space-between; gap: 24px; padding: 42px 0 28px; }
.brand { font: 21px var(--serif); letter-spacing: -.025em; }
nav { display: flex; gap: 26px; color: var(--muted); font-size: 12px; }
nav a[aria-current=page] { color: var(--ink); }
main { flex: 1; }
.geometry { display: flex; justify-content: center; align-items: center; height: 330px; }
.geometry img { width: 260px; height: auto; max-width: 100%; opacity: .8; }
.post-list { padding-bottom: 60px; }
.post-list:empty { padding: 0; }
.post-row { display: grid; grid-template-columns: 94px 1fr 16px; gap: 22px; padding: 24px 0; border-top: 1px solid var(--line); }
.post-date { font: 11px/2 var(--sans); color: var(--muted); font-variant-numeric: tabular-nums; }
.post-row h3 { font: normal 20px/1.5 var(--serif); margin: 0 0 5px; }
.post-row p { font-size: 13px; color: var(--muted); margin: 0; }
.post-arrow { color: var(--muted); font-size: 14px; }
.footer { display: flex; justify-content: space-between; padding: 25px 0 30px; font-size: 10px; color: var(--muted); }
.page-intro { padding: 56px 0 30px; }
.page-intro h1 { margin: 0; font: normal 25px/1.5 var(--serif); }
.article { margin: 55px auto 70px; }
.article h1 { font: normal clamp(27px, 4vw, 36px)/1.5 var(--serif); margin: 30px 0 15px; }
.article-meta { font-size: 11px; color: var(--muted); padding-bottom: 25px; margin-bottom: 32px; border-bottom: 1px solid var(--line); }
.text-link { font-size: 12px; color: var(--muted); }
.prose { font-size: 16px; line-height: 1.8; overflow-wrap: anywhere; }
.prose h2, .prose h3 { font-family: var(--serif); font-weight: normal; line-height: 1.5; margin-top: 36px; }
.prose a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
.prose pre { overflow: auto; background: #f0f1eb; padding: 20px; font-size: 13px; line-height: 1.7; }
.prose code { background: #f0f1eb; padding: 2px 4px; font-size: .9em; }
.prose pre code { padding: 0; }
.prose blockquote { margin: 25px 0; padding: 5px 20px; border-left: 1px solid var(--accent); color: var(--muted); }
.prose img { max-width: 100%; height: auto; }
.skip { position: absolute; left: -9999px; }
.skip:focus { left: 20px; top: 10px; background: var(--paper); padding: 8px; z-index: 2; }
.not-found { text-align: center; padding: 100px 0; }
.not-found h1 { font: normal 36px var(--serif); }
@media (max-width: 600px) {
  .wrap { padding: 0 26px; }
  .header { padding-top: 30px; }
  .brand { font-size: 20px; }
  nav { gap: 20px; }
  .geometry { height: 270px; }
  .geometry img { width: 220px; }
  .post-row { grid-template-columns: 1fr 16px; gap: 8px; }
  .post-date { grid-column: 1 / -1; }
  .article { margin-top: 35px; }
}

/* Cards keep the index quiet; articles open into a wider reading layout. */
.post-list { display: grid; gap: 18px; }
.post-card { display: block; padding: 30px 34px; background: #fffefa; border: 1px solid var(--line); border-radius: 12px; transition: border-color .18s, box-shadow .18s; }
.post-card:hover { color: var(--ink); border-color: #c9d0c1; box-shadow: 0 6px 24px #30332e06; }
.card-meta { display: flex; gap: 18px; color: var(--muted); font-size: 11px; font-variant-numeric: tabular-nums; }
.post-card h3 { font: normal 25px/1.55 var(--serif); margin: 14px 0 10px; }
.post-card p { margin: 0; color: #73766d; font-size: 13px; line-height: 1.9; }
.card-open { display: flex; align-items: center; justify-content: space-between; margin-top: 24px; font-size: 11px; color: var(--accent); }
.article-page .wrap { max-width: 1220px; }
.article-layout { display: grid; grid-template-columns: minmax(0, 790px) minmax(180px, 1fr); gap: 48px; align-items: start; padding: 36px 0 64px; }
.article { min-width: 0; margin: 0; padding: 42px 48px 50px; background: #fffefa; border: 1px solid var(--line); border-radius: 14px; }
.article h1 { font-size: clamp(27px, 3vw, 35px); line-height: 1.5; letter-spacing: -.02em; margin: 26px 0 20px; }
.article-meta { display: flex; flex-wrap: wrap; gap: 20px; padding-bottom: 26px; margin-bottom: 30px; }
.prose { color: #3e413b; line-height: 1.8; }
.prose p { margin: 0 0 16px; }
.prose h2 { color: var(--ink); font-size: 25px; margin: 40px 0 18px; }
.prose h3 { color: var(--ink); font-size: 21px; margin: 28px 0 14px; }
.prose h2, .prose h3 { scroll-margin-top: 35px; }
.prose strong { font-weight: 600; }
.prose ul, .prose ol { padding-left: 24px; margin: 16px 0 20px; }
.prose li { padding-left: 4px; margin-bottom: 6px; }
.math-block { overflow-x: auto; overflow-y: hidden; padding: 8px 4px; margin: 16px 0 20px; max-width: 100%; }
.math-block .katex-display { margin: .6em 0; }
.math-block .katex-display > .katex { white-space: nowrap; }
.prose .katex { font-size: 1.08em; }
.math-error { color: #a64235; }
.desktop-toc { position: sticky; top: 44px; max-height: calc(100vh - 88px); overflow: auto; margin-top: 18px; }
.toc-title { font-size: 11px; color: var(--muted); margin-bottom: 17px; }
.toc-links { display: flex; flex-direction: column; gap: 0; font-size: 12px; }
.toc-links a { display: block; padding: 7px 0 7px 14px; border-left: 1px solid var(--line); line-height: 1.65; color: #7b7e73; }
.toc-links a.toc-level-3 { font-size: 11px; padding-left: 26px; }
.toc-links a:hover, .toc-links a.active { color: var(--accent); border-color: var(--accent); }
.mobile-toc { display: none; }
@media (max-width: 1000px) {
  .article-page .wrap { max-width: 870px; }
  .article-layout { grid-template-columns: minmax(0, 1fr); gap: 0; }
  .desktop-toc { display: none; }
  .mobile-toc { display: block; border-bottom: 1px solid var(--line); padding: 0 0 18px; margin-bottom: 28px; font-size: 12px; color: var(--muted); }
  .mobile-toc summary { cursor: pointer; }
  .mobile-toc .toc-links { margin-top: 14px; }
}
@media (max-width: 600px) {
  .post-card { padding: 24px; }
  .post-card h3 { font-size: 23px; }
  .article-page .wrap { padding: 0 18px; }
  .article-page .header, .article-page .footer { padding-left: 6px; padding-right: 6px; }
  .article-layout { padding-top: 20px; }
  .article { padding: 28px 22px 36px; border-radius: 10px; }
  .article h1 { font-size: 27px; }
  .prose { font-size: 15px; line-height: 1.8; }
  .prose h2 { font-size: 23px; }
  .prose h3 { font-size: 20px; }
  .prose .katex { font-size: 1em; }
  .math-block .katex-display > .katex { text-align: left; }
}
@media (prefers-reduced-motion: reduce) { .post-card { transition: none; } }