:root {
  --bg: #fdfcf9;
  --panel: #ffffff;
  --ink: #1a1a1a;
  --ink-soft: #555;
  --ink-faint: #888;
  --rule: #e7e5e0;
  --accent: #0d4a7a;
  --accent-soft: #e8f1f7;
  --code-bg: #f6f4ee;
  --sans:  system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --serif: ui-serif, Georgia, "Times New Roman", Times, serif;
  --mono:  ui-monospace, "SF Mono", Menlo, Monaco, Consolas, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 {
  font-family: var(--serif);
  font-weight: 500;
  letter-spacing: -0.005em;
}

code, pre, .mono { font-family: var(--mono); }

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

.wrap { max-width: 760px; margin: 0 auto; padding: 0 24px; }

/* ----- top nav ----- */
nav.top {
  position: sticky; top: 0; z-index: 10;
  background: rgba(253,252,249,0.92);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--rule);
}
nav.top .wrap {
  display: flex; align-items: center; justify-content: space-between;
  height: 52px;
  max-width: 1080px;
}
nav.top .brand { font-weight: 600; letter-spacing: -0.01em; }
nav.top .brand a { color: inherit; }
nav.top .brand a:hover { color: var(--accent); text-decoration: none; }
nav.top .links { display: flex; gap: 18px; font-size: 14px; }
nav.top .links a { color: var(--ink-soft); }
nav.top .links a:hover { color: var(--accent); text-decoration: none; }

/* ----- hero ----- */
header.hero { padding: 64px 0 40px; }
header.hero .partof {
  font-size: 13px; color: var(--ink-faint);
  text-transform: uppercase; letter-spacing: 0.08em;
  margin: 0 0 14px;
}
header.hero h1 {
  font-size: 38px; line-height: 1.18; letter-spacing: -0.02em;
  margin: 0 0 8px;
  max-width: 760px;
}
header.hero .lede {
  font-size: 17px; color: var(--ink-soft);
  margin: 16px 0 0;
  max-width: 720px;
}

/* ----- article body ----- */
article { padding-bottom: 24px; }
article section {
  padding: 40px 0;
  border-top: 1px solid var(--rule);
}
article section:first-of-type { border-top: none; padding-top: 8px; }
article h2 {
  font-size: 26px;
  margin: 0 0 18px;
  letter-spacing: -0.015em;
}
article h3 {
  font-size: 18px;
  margin: 32px 0 10px;
  color: var(--ink);
}
article p {
  font-size: 16.5px;
  color: var(--ink);
  margin: 0 0 16px;
}
article p:last-child { margin-bottom: 0; }
article em { font-style: italic; }
article strong { font-weight: 600; }

article ul, article ol {
  font-size: 16.5px;
  color: var(--ink);
  margin: 0 0 18px;
  padding-left: 24px;
  line-height: 1.65;
}
article ul li, article ol li { margin: 8px 0; }

article ul li ul, article ul li ol, article ol li ul, article ol li ol {
  margin: 6px 0 6px;
}

article blockquote {
  margin: 24px 0;
  padding: 6px 20px;
  color: var(--ink-soft);
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  font-style: italic;
}
article blockquote p { margin: 8px 0; font-size: 15.5px; }

article hr {
  border: none;
  border-top: 1px solid var(--rule);
  margin: 40px 0;
}

/* ----- inline code ----- */
article p code,
article li code,
article td code,
article th code,
article h2 code,
article h3 code {
  background: var(--code-bg);
  padding: 1px 6px;
  border-radius: 4px;
  font-size: 0.92em;
  color: #2a4a6a;
}

/* ----- code blocks ----- */
article pre {
  margin: 18px 0;
  padding: 16px 18px;
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-radius: 8px;
  font-size: 13.5px;
  line-height: 1.55;
  overflow-x: auto;
  color: var(--ink);
}
article pre code {
  background: none;
  padding: 0;
  color: inherit;
  font-size: inherit;
}

/* tiny syntax tint for Lean snippets — applied via spans when present */
.kw   { color: #7a3e9d; }
.name { color: #0d4a7a; }
.ty   { color: #2563eb; }
.com  { color: #7a7066; font-style: italic; }
.lit  { color: #b45309; }

/* ----- tables ----- */
.table-wrap { overflow-x: auto; margin: 18px 0; }
article table {
  border-collapse: collapse;
  min-width: 100%;
  font-size: 14px;
}
article table th, article table td {
  padding: 9px 14px;
  border-bottom: 1px solid var(--rule);
  text-align: left;
  white-space: nowrap;
}
article table thead th {
  font-weight: 600;
  color: var(--ink-soft);
  border-bottom: 1px solid var(--ink);
  font-size: 13px;
  text-transform: none;
  letter-spacing: 0;
}
article table td.mono, article table th.mono { font-family: var(--mono); font-size: 13px; }
article table .annot {
  color: var(--ink-faint);
  font-style: italic;
  font-size: 12.5px;
}

/* ----- footnotes ----- */
sup.fnref {
  font-size: 0.75em;
  line-height: 0;
  vertical-align: super;
  margin-left: 1px;
}
sup.fnref a {
  text-decoration: none;
  color: var(--accent);
  padding: 0 2px;
}
sup.fnref a:hover { text-decoration: underline; }

article section.notes {
  padding: 32px 0 40px;
}
article section.notes h2 {
  font-size: 16px;
  font-weight: 600;
  color: var(--ink-faint);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-family: var(--sans);
  margin: 0 0 16px;
}
article ol.footnotes {
  font-size: 14.5px;
  color: var(--ink-soft);
  padding-left: 22px;
  line-height: 1.6;
}
article ol.footnotes li { margin: 10px 0; }
article ol.footnotes li code { font-size: 0.92em; }
.fnback {
  margin-left: 6px;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.95em;
}
.fnback:hover { text-decoration: underline; }

/* ----- footer ----- */
footer.site {
  border-top: 1px solid var(--rule);
  padding: 40px 0 60px;
  font-size: 13px;
  color: var(--ink-faint);
}
footer.site .wrap {
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 12px;
  max-width: 1080px;
}

/* ----- callout for emphasized paragraphs ----- */
article p.callout {
  margin: 24px 0;
  padding: 14px 20px;
  background: var(--accent-soft);
  border-left: 3px solid var(--accent);
  border-radius: 4px;
  color: var(--ink);
  font-size: 16.5px;
  font-style: italic;
}

/* ----- code toggle (details/summary) ----- */
article details.code-toggle {
  margin: 18px 0;
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: var(--code-bg);
  overflow: hidden;
}
article details.code-toggle > summary {
  cursor: pointer;
  padding: 10px 16px;
  font-size: 13.5px;
  color: var(--ink-soft);
  user-select: none;
  list-style: none;
}
article details.code-toggle > summary::-webkit-details-marker {
  display: none;
}
article details.code-toggle > summary::before {
  content: "▸";
  display: inline-block;
  width: 1.2em;
  color: var(--ink-faint);
}
article details.code-toggle[open] > summary::before {
  content: "▾";
}
article details.code-toggle > summary:hover {
  color: var(--accent);
}
article details.code-toggle > summary code {
  background: rgba(0, 0, 0, 0.04);
}
article details.code-toggle > pre {
  margin: 0;
  border: none;
  border-top: 1px solid var(--rule);
  border-radius: 0;
}

/* ----- landing page cards ----- */
.card-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin: 0 0 18px;
}

a.card {
  display: block;
  padding: 18px 22px;
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: var(--panel);
  color: var(--ink);
  text-decoration: none;
  transition: border-color 0.15s ease, background 0.15s ease;
}

a.card:hover {
  border-color: var(--accent);
  background: var(--bg);
  text-decoration: none;
}

.card-label {
  font-size: 12px;
  color: var(--ink-faint);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 6px;
}

.card-title {
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 500;
  color: var(--ink);
  margin: 0 0 8px;
  line-height: 1.3;
  letter-spacing: -0.01em;
}

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

.card-desc {
  font-size: 15px;
  color: var(--ink-soft);
  line-height: 1.55;
  margin: 0;
}

/* responsive */
@media (max-width: 720px) {
  header.hero h1 { font-size: 30px; }
  article h2 { font-size: 22px; }
  article p { font-size: 16px; }
  article ul, article ol { font-size: 16px; }
  nav.top .links { display: none; }
}