:root {
  --bg: #ffffff;
  --text: #18181b;
  --muted: #71717a;
  --border: #e4e4e7;
  --link: #ea580c;
  --link-hover: #c2410c;
  --tag-bg: #fff7ed;
  --tag-text: #9a3412;
  --tag-hover-bg: #fed7aa;
  --accent: #ea580c;
  --learn-bg: #fff7ed;
  --learn-header: #9a3412;
  --learn-border: #fed7aa;
  --summary-text: #3f3f46;
  --code-bg: #f4f4f5;
  --code-color: #be123c;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --max: 720px;
  --gap: 1.75rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1c1917;
    --text: #fafaf9;
    --muted: #a8a29e;
    --border: #44403c;
    --link: #fb923c;
    --link-hover: #f97316;
    --tag-bg: #292524;
    --tag-text: #fdba74;
    --tag-hover-bg: #3c2d1a;
    --accent: #fb923c;
    --learn-bg: #211a12;
    --learn-header: #fdba74;
    --learn-border: #44403c;
    --summary-text: #a8a29e;
    --code-bg: #292524;
    --code-color: #fb7185;
  }
}

*, *::before, *::after { box-sizing: border-box; }

html { font-size: 17px; }

body {
  font-family: var(--sans);
  color: var(--text);
  background: var(--bg);
  line-height: 1.75;
  margin: 0;
  padding: 0 1.25rem;
}

.site-header, main, footer { max-width: var(--max); margin: 0 auto; }

/* ── Header ─────────────────────────────────────────── */
header {
  border-bottom: 2px solid var(--accent);
  margin-bottom: var(--gap);
}

.site-header { padding: var(--gap) 0 1.25rem; }

.site-title {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.03em;
  display: block;
}

.site-title:hover { color: var(--accent); }

.tagline {
  margin: 0.3rem 0 0;
  font-size: 0.7rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-weight: 600;
}

/* ── Footer ─────────────────────────────────────────── */
footer {
  border-top: 1px solid var(--border);
  padding: var(--gap) 0;
  font-size: 0.8rem;
  color: var(--muted);
  letter-spacing: 0.03em;
}
footer p { margin: 0; }
main { padding: var(--gap) 0; min-height: 60vh; }

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

/* ── Post list ───────────────────────────────────────── */
.post-item {
  margin-bottom: 2.25rem;
  padding-bottom: 2.25rem;
  border-bottom: 1px solid var(--border);
}
.post-item:last-child { border-bottom: none; }

.post-item .post-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 0 0 0.3rem;
  line-height: 1.4;
}
.post-item .post-title a { color: var(--text); }
.post-item .post-title a:hover { color: var(--accent); text-decoration: none; }

.post-date {
  font-size: 0.775rem;
  color: var(--muted);
  display: block;
  margin-bottom: 0.4rem;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.post-date::before {
  content: "—";
  color: var(--accent);
  margin-right: 0.4em;
  font-style: normal;
}

.post-summary { margin: 0.35rem 0 0; font-size: 0.95rem; color: var(--summary-text); }

.list-title {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--muted);
  margin: 0 0 var(--gap);
}

/* ── Single post ─────────────────────────────────────── */
.post-header {
  margin-bottom: var(--gap);
  padding-bottom: var(--gap);
  border-bottom: 1px solid var(--border);
}

.post-header h1 {
  font-size: 1.8rem;
  font-weight: 700;
  margin: 0 0 0.6rem;
  letter-spacing: -0.03em;
  line-height: 1.25;
}

.post-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  font-size: 0.8rem;
  color: var(--muted);
}

.post-meta time { letter-spacing: 0.04em; text-transform: uppercase; }

.post-tags { display: flex; gap: 0.4rem; flex-wrap: wrap; }

.tag {
  background: var(--tag-bg);
  color: var(--tag-text);
  padding: 0.2rem 0.55rem;
  border-radius: 3px;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-decoration: none;
}
.tag:hover { background: var(--tag-hover-bg); color: var(--tag-text); text-decoration: none; }

/* ── Post content ────────────────────────────────────── */
.post-content h2 {
  font-size: 1.2rem;
  font-weight: 700;
  margin: 2.25rem 0 0.75rem;
  letter-spacing: -0.02em;
}
.post-content h3 { font-size: 1rem; font-weight: 700; margin: 1.75rem 0 0.5rem; }
.post-content p { margin: 0 0 1.25rem; }
.post-content ul, .post-content ol { margin: 0 0 1.25rem 1.5rem; padding: 0; }
.post-content li { margin-bottom: 0.4rem; }
.post-content blockquote {
  border-left: 2px solid var(--accent);
  margin: 1.75rem 0;
  padding: 0.4rem 0 0.4rem 1.25rem;
  color: var(--muted);
  font-style: italic;
}

/* Tables */
.post-content table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; font-size: 0.9rem; }
.post-content th {
  text-align: left;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  border-bottom: 2px solid var(--border);
  padding: 0.4rem 0.75rem;
}
.post-content td { padding: 0.5rem 0.75rem; border-bottom: 1px solid var(--border); }
.post-content tr:last-child td { border-bottom: none; }

/* Code */
.post-content code {
  font-family: var(--mono);
  font-size: 0.85em;
  background: var(--code-bg);
  padding: 0.15em 0.4em;
  border-radius: 3px;
  color: var(--code-color);
}
.post-content pre { overflow-x: auto; margin: 1.5rem 0; padding: 1rem 1.25rem; font-size: 0.85rem; border-radius: 6px; }
.post-content pre code { background: none; padding: 0; color: inherit; font-size: inherit; }
.highlight { border-radius: 6px; overflow: hidden; margin: 1.5rem 0; }

/* KaTeX display blocks */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.25rem 0; }

/* ── Learning shortcode ──────────────────────────────── */
.learning {
  border-left: 3px solid var(--accent);
  background: var(--learn-bg);
  border-radius: 0 6px 6px 0;
  margin: 2rem 0;
}

.learning summary {
  cursor: pointer;
  padding: 0.85rem 1.1rem;
  font-weight: 700;
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  user-select: none;
  color: var(--learn-header);
}
.learning summary::-webkit-details-marker { display: none; }
.learning summary::before {
  content: "›";
  font-size: 1.2rem;
  color: var(--accent);
  transition: transform 0.2s ease;
  display: inline-block;
  line-height: 1;
  font-weight: 400;
}
.learning[open] summary::before { transform: rotate(90deg); }

.learning-content {
  padding: 0 1.1rem 1.1rem;
  border-top: 1px solid var(--learn-border);
  font-size: 0.95rem;
}
.learning-content > *:first-child { margin-top: 0.85rem; }
.learning-content > *:last-child { margin-bottom: 0; }

/* ── Back link ───────────────────────────────────────── */
.post-footer { margin-top: 2.5rem; padding-top: var(--gap); border-top: 1px solid var(--border); }
.back-link { font-size: 0.85rem; color: var(--muted); font-weight: 600; letter-spacing: 0.03em; }
.back-link:hover { color: var(--accent); }

/* ── Pagination ──────────────────────────────────────── */
.pagination { display: flex; gap: 0.5rem; margin-top: var(--gap); font-size: 0.875rem; }

/* ── Mobile ──────────────────────────────────────────── */
@media (max-width: 600px) {
  html { font-size: 16px; }
  body { padding: 0 1rem; }
  .post-header h1 { font-size: 1.5rem; }
  .site-title { font-size: 1.35rem; }
}