:root {
  --page-width: 920px;
  --bg: #fdfdfc;
  --ink: #18181b;
  --muted: #6b7280;
  --faint: #9ca3af;
  --line: #e7e5e4;
  --accent: #1d4ed8;
  --accent-soft: #eff4ff;
  --card: #ffffff;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, "Helvetica Neue", sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

/* ---------- nav ---------- */
nav.topnav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(253,253,252,.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  max-width: var(--page-width); margin: 0 auto; padding: 14px 24px;
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
}
.nav-name { font-weight: 700; font-size: 15px; color: var(--ink); letter-spacing: -.01em; }
.nav-name:hover { text-decoration: none; color: var(--accent); }
.nav-links { display: flex; gap: 18px; flex-wrap: wrap; }
.nav-links a { color: var(--muted); font-size: 13.5px; font-weight: 500; }
.nav-links a:hover { color: var(--ink); text-decoration: none; }
.nav-links a.active { color: var(--ink); font-weight: 700; }

main { max-width: var(--page-width); margin: 0 auto; padding: 0 24px 80px; }

/* ---------- front page hero ---------- */
.hero { display: flex; gap: 36px; align-items: center; padding: 56px 0 40px; }
.hero h1 { font-size: 32px; letter-spacing: -.03em; line-height: 1.15; font-weight: 800; }
.hero .kr { color: var(--faint); font-weight: 500; font-size: 22px; margin-left: 6px; }
.hero .role { margin-top: 8px; color: var(--muted); font-size: 16px; }
.hero .role a { color: var(--muted); border-bottom: 1px solid var(--line); }
.hero .role a:hover { color: var(--accent); text-decoration: none; border-color: var(--accent); }
.hero-links { margin-top: 16px; display: flex; flex-wrap: wrap; gap: 10px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 13px; font-weight: 600; color: var(--ink);
  border: 1px solid var(--line); background: var(--card);
  padding: 6px 13px; border-radius: 100px;
  transition: border-color .15s, background .15s;
}
.chip:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; background: var(--accent-soft); }

.bio { color: #3f3f46; font-size: 16.5px; }
.bio strong { font-weight: 650; }
.callout {
  margin-top: 20px; padding: 14px 18px; border-radius: 10px;
  background: var(--accent-soft); border: 1px solid #dbe6ff;
  font-size: 15px; color: #1e3a8a;
}

/* ---------- sections ---------- */
section { padding-top: 56px; }
h2.sec {
  font-size: 26px; letter-spacing: -.02em;
  color: var(--ink); font-weight: 800; margin-bottom: 18px;
}
.h2row { display: flex; align-items: baseline; justify-content: space-between; margin-bottom: 20px; }
.h2row h2.sec { margin-bottom: 0; }
.h2row a { font-size: 13.5px; font-weight: 500; }

/* ---------- subpage header ---------- */
.page-head { padding: 48px 0 0; }
.page-head h1 { font-size: 30px; letter-spacing: -.03em; font-weight: 800; }
.page-head p { margin-top: 8px; color: var(--muted); font-size: 15px; max-width: 620px; }
.toc-chips { margin-top: 18px; display: flex; gap: 8px; flex-wrap: wrap; }

/* ---------- news ---------- */
.news-item { display: flex; gap: 18px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.news-item:last-child { border-bottom: 0; }
.news-date { flex-shrink: 0; width: 76px; color: var(--faint); font-size: 13.5px; font-variant-numeric: tabular-nums; padding-top: 2px; }
.news-body { font-size: 15.5px; }
.news-by { color: var(--faint); font-size: 13.5px; white-space: nowrap; }

/* ---------- research areas ---------- */
.areas { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.area {
  border: 1px solid var(--line); border-radius: 14px; padding: 20px;
  background: var(--card); transition: box-shadow .2s, transform .2s;
}
.area:hover { box-shadow: 0 10px 30px rgba(0,0,0,.06); transform: translateY(-2px); }
.area h3 { font-size: 15.5px; letter-spacing: -.01em; margin-bottom: 8px; font-weight: 700; }
.area p { font-size: 13.5px; color: var(--muted); line-height: 1.55; }

/* ---------- publications ---------- */
.year-head {
  font-size: 16.5px; font-weight: 750; letter-spacing: -.01em;
  margin: 30px 0 2px; padding-bottom: 7px; border-bottom: 1px solid var(--line);
}
section .year-head:first-of-type { margin-top: 24px; }
.pub { padding: 16px 0; border-bottom: 1px solid var(--line); }
.pub:last-child { border-bottom: 0; }
.pub-title { font-weight: 650; font-size: 15.5px; letter-spacing: -.01em; }
.pub-title a { color: var(--ink); }
.pub-title a:hover { color: var(--accent); text-decoration: none; }
.pub-authors { color: var(--muted); font-size: 13.5px; margin-top: 3px; }
.pub-meta { margin-top: 6px; display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.venue {
  font-size: 12px; font-weight: 700; padding: 2px 9px; border-radius: 6px;
  background: #f4f4f5; color: #52525b; letter-spacing: .01em; white-space: nowrap;
}
.venue.top { background: var(--accent-soft); color: var(--accent); }
.venue-full { color: var(--muted); font-size: 13.5px; }
.award-pill {
  font-size: 12px; font-weight: 700; padding: 2px 9px; border-radius: 6px;
  background: #fef3c7; color: #92400e; white-space: nowrap;
}
.plink {
  font-size: 12px; font-weight: 700; padding: 2px 10px; border-radius: 100px;
  text-decoration: none; white-space: nowrap;
}
.plink:hover { text-decoration: none; filter: brightness(.92); }
.plink.paper { background: #eff4ff; color: #1d4ed8; }
.plink.slide { background: #fef3c7; color: #b45309; }
.plink.code  { background: #dcfce7; color: #15803d; }
.plink.demo  { background: #f3e8db; color: #92400e; }
.cofirst { color: var(--faint); font-size: 12.5px; margin-top: 4px; }

/* ---------- highlights / honors ---------- */
.hl-grid { display: grid; grid-template-columns: 1fr; gap: 2px; }
.hl { display: flex; gap: 14px; align-items: baseline; font-size: 14.5px; padding: 7px 0; border-bottom: 1px dotted var(--line); }
.hl:last-child { border-bottom: 0; }
.hl .yr { color: var(--faint); font-size: 13px; flex-shrink: 0; width: 62px; font-variant-numeric: tabular-nums; }

/* ---------- people ---------- */
.people-cols { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; }
.people-cols h3 { font-size: 16px; font-weight: 700; margin-bottom: 10px; }
.people-cols ul { list-style: none; }
.people-cols li { font-size: 14.5px; padding: 4px 0; color: #3f3f46; }
.alum { padding: 12px 0; border-bottom: 1px dotted var(--line); }
.alum:last-child { border-bottom: 0; }
.alum-name { font-weight: 650; font-size: 15px; }
.alum-name a { color: var(--ink); }
.alum-name a:hover { color: var(--accent); }
.alum-deg { color: var(--faint); font-weight: 400; font-size: 13.5px; margin-left: 6px; }
.alum-note { color: var(--muted); font-size: 13.5px; margin-top: 2px; }

/* ---------- generic rows (teaching, service) ---------- */
.row { display: flex; gap: 18px; padding: 9px 0; border-bottom: 1px dotted var(--line); font-size: 15px; align-items: baseline; }
.row:last-child { border-bottom: 0; }
.row .lead { flex-shrink: 0; width: 120px; color: var(--faint); font-size: 13.5px; }
.row .grow { flex: 1; }
.row .trail { color: var(--muted); font-size: 14px; text-align: right; }

/* ---------- group labels ---------- */
.subhead {
  font-size: 19px; letter-spacing: -.015em;
  color: var(--ink); font-weight: 700; margin: 32px 0 8px;
}

/* ---------- footer ---------- */
footer.sitefoot {
  border-top: 1px solid var(--line); margin-top: 72px; padding: 28px 24px;
  text-align: center; color: var(--faint); font-size: 13.5px;
}

@media (max-width: 640px) {
  .hero { flex-direction: column; text-align: center; align-items: center; gap: 24px; padding-top: 40px; }
  .hero-links { justify-content: center; }
  .areas { grid-template-columns: 1fr; }
  .people-cols { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .row { flex-wrap: wrap; }
  .row .trail { text-align: left; }
}