:root {
  --ink: #1a1a1a;
  --ink-muted: #555;
  --ink-faint: #888;
  --rule: #e6e6e6;
  --bg: #fdfdfc;
  --card-bg: #f7f6f2;
  --accent: #1a2b4a;
  --accent-hover: #3a5a9a;
  --measure: 44rem;
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Charter", "Iowan Old Style", "Georgia", "Cambria", serif;
  font-size: 18px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.wrap {
  max-width: 52rem;
  margin: 0 auto;
  padding: 3rem 1.5rem 4rem;
}

/* ---- Site nav ---- */

.site-nav {
  border-bottom: 1px solid var(--rule);
  background: var(--bg);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav-inner {
  max-width: 52rem;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
}
.nav-brand {
  font-family: "Charter", "Iowan Old Style", Georgia, serif;
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--ink);
  border-bottom: none;
  letter-spacing: 0.01em;
}
.nav-brand:hover { color: var(--accent); }
.site-nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  gap: 1.25rem;
  font-size: .95rem;
}
.site-nav a {
  color: var(--ink-muted);
  border-bottom: none;
}
.site-nav a:hover { color: var(--accent); }
.site-nav a[aria-current="page"] {
  color: var(--ink);
  border-bottom: 1px solid var(--ink);
  padding-bottom: 2px;
}

/* ---- Page header (non-home pages) ---- */

.page-header {
  margin-bottom: 2.5rem;
}
.page-header h1 {
  font-size: 2rem;
  margin: 0 0 .5rem;
  letter-spacing: -0.01em;
}
.page-header p {
  margin: 0;
  max-width: var(--measure);
  font-size: 1rem;
}

/* ---- Site footer ---- */

.site-footer {
  border-top: 1px solid var(--rule);
  padding: 2rem 0;
  margin-top: 2rem;
  color: var(--ink-muted);
  font-size: .9rem;
}
.site-footer .wrap {
  padding-top: 0;
  padding-bottom: 0;
}
.site-footer p { margin: 0 0 .25rem; }

/* ---- Course list ---- */

.course-list {
  list-style: none;
  padding: 0;
  margin: 0;
  max-width: var(--measure);
}
.course-list li {
  padding: .5rem 0;
  border-bottom: 1px dotted var(--rule);
}
.course-list li:last-child { border-bottom: none; }

/* ---- Paper cards with expandable abstracts ---- */

.paper.card {
  background: var(--card-bg);
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 1.1rem 1.3rem;
  margin: 0 0 1rem;
  max-width: var(--measure);
  transition: border-color .15s ease, box-shadow .15s ease;
}
.paper.card:hover {
  border-color: #d4d0c4;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}
.paper.card h3 {
  font-size: 1.05rem;
  margin: 0 0 .3rem;
  font-weight: 600;
  line-height: 1.35;
}
.paper.card .authors,
.paper.card .venue {
  margin: 0;
  color: var(--ink-muted);
  font-size: .92rem;
  line-height: 1.5;
}
.paper.card .venue { margin-top: .1rem; }
.paper.card .paper-links {
  margin: .5rem 0 0;
  font-size: .88rem;
}

.paper.card .abstract {
  margin-top: .8rem;
  padding-top: .8rem;
  border-top: 1px dashed var(--rule);
}
.paper.card .abstract > summary {
  cursor: pointer;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .82rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-muted);
  list-style: none;
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  user-select: none;
}
.paper.card .abstract > summary::-webkit-details-marker { display: none; }
.paper.card .abstract > summary::before {
  content: "▸";
  font-size: .75rem;
  transition: transform .15s ease;
  color: var(--ink-faint);
}
.paper.card .abstract[open] > summary::before {
  transform: rotate(90deg);
}
.paper.card .abstract > summary:hover {
  color: var(--accent);
}
.paper.card .abstract > p {
  margin: .7rem 0 0;
  font-size: .95rem;
  color: var(--ink);
  line-height: 1.6;
}

/* ---- Table of contents (resources page) ---- */

.toc {
  background: var(--card-bg);
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  margin: 0 0 2.5rem;
  font-size: .92rem;
}
.toc-title {
  margin: 0 0 .6rem;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faint);
}
.toc ul {
  list-style: none;
  padding: 0;
  margin: 0;
  columns: 2;
  column-gap: 2rem;
}
.toc li {
  padding: .15rem 0;
  break-inside: avoid;
}
.toc a {
  color: var(--ink-muted);
  border-bottom: none;
}
.toc a:hover { color: var(--accent); }

/* ---- Resource lists ---- */

.resource-list {
  list-style: disc;
  padding-left: 1.2rem;
  margin: 0 0 1rem;
  max-width: var(--measure);
  color: var(--ink);
}
.resource-list li {
  padding: .2rem 0;
  line-height: 1.55;
}
.resource-list li::marker { color: var(--ink-faint); }

/* ---- Tip callout ---- */

.tip {
  background: #f4f1e8;
  border-left: 3px solid #c9a85d;
  padding: .8rem 1rem;
  margin: 1rem 0;
  max-width: var(--measure);
  font-size: .95rem;
  border-radius: 0 4px 4px 0;
}

/* ---- YoHo updates list ---- */

.updates {
  list-style: none;
  padding: 0;
  margin: 0;
  max-width: var(--measure);
}
.updates li {
  display: grid;
  grid-template-columns: 9rem 1fr;
  gap: 1rem;
  padding: .75rem 0;
  border-bottom: 1px dotted var(--rule);
}
.updates li:last-child { border-bottom: none; }
.updates .date {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: .85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--ink-faint);
  padding-top: .05rem;
}

/* ---- Simple links list (financial-literacy etc) ---- */

.links-list {
  list-style: none;
  padding: 0;
  margin: 0 0 1rem;
  max-width: var(--measure);
}
.links-list li {
  padding: .3rem 0;
}

code {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: .88em;
  background: var(--card-bg);
  padding: 0.1rem 0.3rem;
  border-radius: 3px;
}

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid rgba(26, 43, 74, 0.25);
  transition: color .15s ease, border-color .15s ease;
}
a:hover {
  color: var(--accent-hover);
  border-bottom-color: var(--accent-hover);
}

h1, h2, h3 {
  font-family: "Charter", "Iowan Old Style", "Georgia", serif;
  font-weight: 600;
  color: var(--ink);
  line-height: 1.25;
}

/* ---- Hero ---- */

.hero {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: 2rem;
  align-items: start;
  margin-bottom: 1rem;
}

.photo {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  overflow: hidden;
  background: #eee;
  position: relative;
}
.photo img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.photo-fallback {
  display: none;
  position: absolute;
  inset: 0;
  align-items: center;
  justify-content: center;
  background: var(--accent);
  color: #fff;
  font-family: "Charter", Georgia, serif;
  font-size: 3rem;
  font-weight: 600;
}

.intro h1 {
  font-size: 2.25rem;
  margin: 0 0 .5rem;
  letter-spacing: -0.01em;
}
.intro .lede {
  color: var(--ink);
  font-size: 1.05rem;
  margin: 0 0 1rem;
}
.intro p {
  margin: 0 0 1rem;
  color: var(--ink);
}

.links {
  list-style: none;
  padding: 0;
  margin: 1.25rem 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: .4rem .9rem;
  font-size: .95rem;
}
.links li { margin: 0; }
.links a {
  border-bottom: none;
  color: var(--ink-muted);
}
.links a:hover { color: var(--accent); }

/* ---- Sections ---- */

section {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--rule);
}

section > h2 {
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faint);
  margin: 0 0 1.5rem;
}

section > p {
  margin: 0 0 1rem;
  max-width: var(--measure);
}

/* ---- Papers ---- */

.paper {
  margin: 0 0 1.75rem;
  max-width: var(--measure);
}

.paper h3 {
  font-size: 1.1rem;
  margin: 0 0 .25rem;
  font-weight: 600;
  line-height: 1.35;
}

.paper .authors {
  margin: 0;
  color: var(--ink-muted);
  font-size: .95rem;
}

.paper .venue {
  margin: .1rem 0 .3rem;
  color: var(--ink-muted);
  font-size: .95rem;
}

.paper .paper-links {
  margin: .25rem 0 0;
  font-size: .9rem;
  color: var(--ink-faint);
}
.paper .paper-links a {
  color: var(--accent);
  border-bottom: 1px solid rgba(26, 43, 74, 0.2);
}
.paper .paper-links a:hover {
  border-bottom-color: var(--accent-hover);
}

/* ---- WIP, Outreach, Teaching ---- */

.wip, .outreach {
  list-style: none;
  padding: 0;
  margin: 0;
  max-width: var(--measure);
}
.wip li, .outreach li {
  padding: .25rem 0;
  color: var(--ink);
}
.wip li { border-bottom: 1px dotted var(--rule); padding: .5rem 0; }
.wip li:last-child { border-bottom: none; }

.outreach li { margin-bottom: .6rem; }

.teaching h3 {
  font-size: 1rem;
  font-weight: 600;
  margin: 1.25rem 0 .25rem;
  color: var(--ink);
}
.teaching ul {
  margin: 0 0 .5rem 1.25rem;
  padding: 0;
  color: var(--ink-muted);
}
.teaching li {
  padding: .1rem 0;
}

.muted { color: var(--ink-muted); }
.small { font-size: .85rem; }

/* ---- Responsive ---- */

@media (max-width: 640px) {
  body { font-size: 17px; }
  .wrap { padding: 2rem 1.25rem 3rem; }
  .nav-inner {
    padding: .75rem 1.25rem;
    gap: .5rem .9rem;
  }
  .site-nav ul {
    gap: .5rem .9rem;
    font-size: .9rem;
  }
  .hero {
    grid-template-columns: 1fr;
    gap: 1.25rem;
  }
  .photo {
    width: 128px;
    height: 128px;
  }
  .intro h1 { font-size: 1.85rem; }
  .page-header h1 { font-size: 1.65rem; }
  .toc ul { columns: 1; }
  .updates li {
    grid-template-columns: 1fr;
    gap: .1rem;
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e8e6e3;
    --ink-muted: #b0ada7;
    --ink-faint: #888583;
    --rule: #2a2a2a;
    --bg: #141414;
    --card-bg: #1c1c1c;
    --accent: #9fb6e8;
    --accent-hover: #c7d4f2;
  }
  .photo { background: #222; }
  .tip {
    background: #262013;
    border-left-color: #8a6d2f;
  }
}