:root {
  --bg: #fdfdfc;
  --bg-card: #f5f5f3;
  --text: #1f2328;
  --text-soft: #4b5563;
  --text-faint: #8a929c;
  --accent: #1a56db;
  --accent-soft: #e8effc;
  --border: #e5e7e9;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 4px 14px rgba(0,0,0,.05);
  --tag-paper-bg: #e3edff;  --tag-paper-fg: #1d4fd7;
  --tag-role-bg: #f1e6ff;   --tag-role-fg: #7c3aed;
  --tag-milestone-bg: #def7e4; --tag-milestone-fg: #15803d;
  --tag-release-bg: #fff0dd;   --tag-release-fg: #c2570a;
  --tag-award-bg: #fdeaea;     --tag-award-fg: #c01c28;
  --tag-talk-bg: #e0f4f7;      --tag-talk-fg: #0e7490;
}
html[data-theme="dark"] {
  --bg: #15181d;
  --bg-card: #1d2127;
  --text: #e8eaed;
  --text-soft: #b4bac3;
  --text-faint: #7d8590;
  --accent: #7aa2ff;
  --accent-soft: #1d2740;
  --border: #2b3038;
  --shadow: 0 1px 3px rgba(0,0,0,.4), 0 4px 14px rgba(0,0,0,.3);
  --tag-paper-bg: #1d2c4f;  --tag-paper-fg: #93b4ff;
  --tag-role-bg: #2d1d4f;   --tag-role-fg: #c4a5ff;
  --tag-milestone-bg: #143524; --tag-milestone-fg: #6ee7a0;
  --tag-release-bg: #3d2a12;   --tag-release-fg: #ffb46b;
  --tag-award-bg: #43181c;     --tag-award-fg: #ff9da4;
  --tag-talk-bg: #0e2a30;      --tag-talk-fg: #67d3e0;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 15.5px;
  line-height: 1.65;
  transition: background .25s, color .25s;
}
.container { max-width: 840px; margin: 0 auto; padding: 0 24px 60px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
b, strong { font-weight: 600; }

/* ---------- top nav ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  max-width: 840px; margin: 0 auto; padding: 10px 24px;
  display: flex; align-items: center; gap: 12px;
}
.nav-tabs {
  display: flex; gap: 4px; flex: 1; overflow-x: auto;
  scrollbar-width: none;
}
.nav-tabs::-webkit-scrollbar { display: none; }
.nav-tabs a {
  padding: 6px 13px; border-radius: 999px;
  color: var(--text-soft); font-size: .9rem; font-weight: 500;
  white-space: nowrap; transition: background .15s, color .15s;
}
.nav-tabs a:hover { background: var(--bg-card); color: var(--text); text-decoration: none; }
.nav-tabs a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.theme-toggle {
  flex: 0 0 auto;
  background: var(--bg-card); border: 1px solid var(--border);
  color: var(--text-soft); border-radius: 999px;
  width: 36px; height: 36px; cursor: pointer; font-size: 16px;
  display: flex; align-items: center; justify-content: center;
  transition: transform .15s;
}
.theme-toggle:hover { transform: scale(1.08); }

/* ---------- page title (subpages) ---------- */
h1.page-title {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 2rem; font-weight: 700; margin: 38px 0 6px;
  letter-spacing: -.01em;
}
.page-sub { color: var(--text-faint); font-size: .92rem; margin: 0 0 26px; }

/* ---------- hero ---------- */
.hero { display: flex; gap: 36px; align-items: flex-start; margin-top: 36px; }
.hero-text { flex: 1; min-width: 0; }
h1.name {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 2.35rem; font-weight: 700; margin: 0 0 4px;
  letter-spacing: -.01em;
}
.name-cn { font-size: 1.25rem; color: var(--text-faint); font-weight: 500; margin-left: 10px; }
.role-line { color: var(--text-soft); font-weight: 500; margin: 2px 0 18px; }
.hero-text p { margin: 0 0 13px; color: var(--text-soft); }
.hero-text p a { font-weight: 500; }
.avatar-wrap { flex: 0 0 215px; text-align: center; }
.avatar-wrap a {
  display: block; width: 215px; height: 215px; margin: 0 auto;
  border-radius: 18px; box-shadow: var(--shadow);
  border: 1px solid var(--border); overflow: hidden;
}
.avatar-wrap img {
  width: 100%; height: 100%; object-fit: cover;
}
.avatar-default { transform: scale(1.25); object-position: 60% 50%; filter: brightness(1.12) saturate(0.9) hue-rotate(-3deg); }
.avatar-hover { object-position: 40% 50%; }
.avatar-caption { font-size: .8rem; color: var(--text-faint); margin-top: 8px; }
.avatar-wrap .avatar-hover,
.avatar-wrap:hover .avatar-default { display: none; }
.avatar-wrap:hover .avatar-hover { display: block; }
.avatar-wrap .caption-hover,
.avatar-wrap:hover .caption-default { display: none; }
.avatar-wrap:hover .caption-hover { display: inline; }

/* ---------- social links ---------- */
.links { display: flex; flex-wrap: wrap; gap: 9px; margin-top: 18px; }
.links a {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 7px 14px; border-radius: 999px;
  background: var(--bg-card); border: 1px solid var(--border);
  color: var(--text-soft); font-size: .86rem; font-weight: 500;
  transition: border-color .15s, color .15s;
}
.links a:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }
.links svg { width: 15px; height: 15px; fill: currentColor; }

/* ---------- hiring card ---------- */
.callout {
  display: flex; gap: 14px; align-items: flex-start;
  margin-top: 26px; padding: 15px 18px;
  background: var(--accent-soft); border: 1px solid var(--border);
  border-left: 4px solid var(--accent); border-radius: 10px;
  color: var(--text-soft); font-size: .92rem;
}
.callout .emoji { font-size: 1.3rem; line-height: 1.3; }

/* ---------- sections ---------- */
section { margin-top: 52px; }
h2.sec {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 1.5rem; font-weight: 700; margin: 0 0 6px;
  padding-bottom: 10px; border-bottom: 1px solid var(--border);
  display: flex; align-items: baseline; justify-content: space-between; gap: 12px;
}
h2.sec .view-all { font-family: 'Inter', sans-serif; font-size: .85rem; font-weight: 500; white-space: nowrap; }
.sec-sub { color: var(--text-faint); font-size: .9rem; margin: 8px 0 22px; }

/* ---------- news ---------- */
.news { list-style: none; margin: 18px 0 0; padding: 0; }
.news li {
  display: grid; grid-template-columns: 86px 86px 1fr;
  gap: 12px; align-items: baseline;
  padding: 7px 0; font-size: .93rem; color: var(--text-soft);
}
.news .date { color: var(--text-faint); font-variant-numeric: tabular-nums; white-space: nowrap; }
.tag {
  justify-self: start; align-self: center;
  font-size: .7rem; font-weight: 600; letter-spacing: .04em;
  padding: 2px 9px; border-radius: 999px; text-transform: uppercase;
  white-space: nowrap;
}
.tag.paper     { background: var(--tag-paper-bg);     color: var(--tag-paper-fg); }
.tag.role      { background: var(--tag-role-bg);      color: var(--tag-role-fg); }
.tag.milestone { background: var(--tag-milestone-bg); color: var(--tag-milestone-fg); }
.tag.release   { background: var(--tag-release-bg);   color: var(--tag-release-fg); }
.tag.award     { background: var(--tag-award-bg);     color: var(--tag-award-fg); }
.tag.talk      { background: var(--tag-talk-bg);      color: var(--tag-talk-fg); }
.year-divider {
  font-family: 'Source Serif 4', Georgia, serif;
  font-size: 1.15rem; font-weight: 600; color: var(--text);
  margin: 26px 0 4px; padding-bottom: 6px; border-bottom: 1px dashed var(--border);
}

/* ---------- experience ---------- */
.exp { display: flex; gap: 18px; align-items: center; padding: 16px 0; border-bottom: 1px solid var(--border); }
.exp:last-child { border-bottom: none; }
.exp .logo {
  flex: 0 0 110px; height: 72px; display: flex; align-items: center; justify-content: center;
  background: #fff; border: 1px solid var(--border); border-radius: 10px; overflow: hidden;
}
.exp .logo img { max-width: 92%; max-height: 88%; object-fit: contain; }
#research-projects .exp .logo { flex: 0 0 150px; height: 98px; }
#internships .exp .logo { flex: 0 0 135px; height: 88px; }
.exp .body { flex: 1; min-width: 0; }
.exp .title { font-weight: 600; }
.exp .period { color: var(--text-faint); font-size: .85rem; }
.exp .desc { color: var(--text-soft); font-size: .91rem; margin-top: 3px; }

/* ---------- publications ---------- */
.pub {
  display: flex; gap: 20px; padding: 22px 0;
  border-bottom: 1px solid var(--border); align-items: center;
}
.pub:last-child { border-bottom: none; }
.pub .thumb {
  flex: 0 0 235px; width: 235px;
  border-radius: 10px; overflow: hidden;
  border: 1px solid var(--border); box-shadow: var(--shadow);
  background: var(--bg-card);
}
.pub .thumb img, .pub .thumb video { display: block; width: 100%; height: auto; }
/* hover swap: show alternate image/video when hovering the thumbnail */
.pub .thumb.swap { display: grid; }
.pub .thumb.swap > * { grid-area: 1 / 1; transition: opacity .25s ease; }
.pub .thumb.swap .swap-hover { opacity: 0; }
.pub .thumb.swap:hover .swap-hover { opacity: 1; }
.pub .thumb.swap:hover .swap-default { opacity: 0; }
.pub .body { flex: 1; min-width: 0; }
.pub .title { font-weight: 600; font-size: 1.02rem; line-height: 1.45; color: var(--text); }
.pub .title a { color: inherit; }
.pub .title a:hover { color: var(--accent); }
.pub .authors { color: var(--text-soft); font-size: .89rem; margin-top: 5px; }
.pub .authors b { color: var(--text); }
.pub .venue { margin-top: 7px; font-size: .85rem; }
.venue-badge {
  display: inline-block; font-size: .74rem; font-weight: 600;
  padding: 2px 10px; border-radius: 999px;
  background: var(--accent-soft); color: var(--accent);
}
.venue-badge.oral { background: var(--tag-award-bg); color: var(--tag-award-fg); }
.pub .pub-links { margin-top: 8px; font-size: .88rem; display: flex; flex-wrap: wrap; gap: 4px 14px; align-items: center; }
.pub .note { color: var(--text-faint); font-size: .85rem; margin-top: 7px; }
.pub .pub-links img { vertical-align: middle; }

/* ---------- simple lists ---------- */
.plain { margin: 14px 0 0; padding-left: 20px; color: var(--text-soft); }
.plain li { margin-bottom: 8px; }
.plain .date { color: var(--text-faint); font-size: .88rem; margin-right: 6px; }

/* ---------- note cards (notes page) ---------- */
.note-card {
  display: block; padding: 16px 18px; margin-top: 14px;
  background: var(--bg-card); border: 1px solid var(--border); border-radius: 12px;
  transition: border-color .15s;
}
.note-card:hover { border-color: var(--accent); text-decoration: none; }
.note-card .nc-date { font-size: .78rem; color: var(--text-faint); text-transform: uppercase; letter-spacing: .05em; }
.note-card .nc-title { font-weight: 600; color: var(--text); margin-top: 3px; }
.note-card .nc-desc { font-size: .88rem; color: var(--text-soft); margin-top: 4px; }

/* ---------- footer ---------- */
footer {
  margin-top: 70px; padding-top: 18px; border-top: 1px solid var(--border);
  font-size: .82rem; color: var(--text-faint); text-align: center;
}

/* ---------- responsive ---------- */
@media (max-width: 760px) {
  .hero { flex-direction: column-reverse; align-items: center; }
  .avatar-wrap { flex: none; }
  .avatar-wrap a { width: 180px; height: 180px; border-radius: 50%; }
  h1.name { font-size: 1.85rem; }
  .news li { grid-template-columns: 74px 1fr; }
  .news li .tag { display: none; }
  .pub { flex-direction: column; align-items: stretch; }
  .pub .thumb { flex: none; width: 100%; max-width: 360px; margin: 0 auto; }
  .exp .logo { flex: 0 0 84px; height: 58px; }
}