/* =============================================================
   Kai (Kevin) Xu 鈥?homepage stylesheet
   Shared by index.html / publications.html / group.html
   Style reference: https://hangzhaomit.github.io/
   No framework, no build step.
   ============================================================= */

/* ---------- tokens ---------- */
:root{
  --ink:#1c1c1e;
  --ink-2:#4a4a4f;
  --ink-3:#86868b;
  --rule:#e3e3e6;
  --link:#1a5fb4;
  --link-hover:#0b3d78;
  --bg:#ffffff;
  --tint:#f6f6f7;
  --max:80vw;
  --max-wide:1280px;
}

/* ---------- reset ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body{
  margin:0;
  background:var(--bg);
  color:var(--ink);
  font:400 16.5px/1.72 -apple-system,BlinkMacSystemFont,"Segoe UI","Helvetica Neue",Helvetica,Arial,
       "PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  -webkit-font-smoothing:antialiased;
}
img{max-width:100%;display:block}
a{color:var(--link);text-decoration:none}
a:hover{color:var(--link-hover);text-decoration:underline}
h1,h2,h3,h4{font-weight:600;letter-spacing:-.012em;margin:0}
p{margin:0 0 1.05em}
ul{margin:0;padding:0;list-style:none}

/* ---------- layout ---------- */
.wrap{width:var(--max);max-width:var(--max-wide);margin:0 auto;padding:0 28px}
section{padding:52px 0}
section+section{border-top:1px solid var(--rule)}

/* ---------- nav ---------- */
.nav{
  position:sticky;top:0;z-index:50;
  background:rgba(255,255,255,.88);
  backdrop-filter:saturate(180%) blur(14px);
  -webkit-backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid var(--rule);
}
.nav .wrap{display:flex;align-items:center;justify-content:space-between;height:52px}
.nav .home{font-size:13px;font-weight:600;letter-spacing:.1em;text-transform:uppercase;color:var(--ink)}
.nav ul{display:flex;gap:22px;flex-wrap:wrap}
.nav a{font-size:12.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-2)}
.nav a:hover{color:var(--ink);text-decoration:none}
.nav a.on{color:var(--ink);font-weight:600}

/* ---------- hero ---------- */
.hero{padding-top:60px;padding-bottom:46px}
.hero h1{font-size:44px;line-height:1.1;letter-spacing:-.024em}
.hero h1 .cn{font-size:.62em;font-weight:400;color:var(--ink-3);letter-spacing:0;margin-left:.35em}
.hero .role{margin-top:14px;font-size:17px;color:var(--ink-2);max-width:640px}

/* page hero for subpages */
.phero{padding:54px 0 8px}
.phero h1{font-size:34px;letter-spacing:-.02em}
.phero .role{margin-top:10px;font-size:16px;color:var(--ink-2);max-width:680px}

.split{display:grid;grid-template-columns:1fr 232px;gap:46px;align-items:start;margin-top:34px}
.bio p:last-child{margin-bottom:0}
.recruit{
  margin-top:22px;padding:16px 18px;
  background:var(--tint);border-left:3px solid var(--ink);border-radius:0 6px 6px 0;
  font-size:15.5px;
}
.recruit strong{font-weight:600}

.card{position:relative}
.portrait{width:100%;aspect-ratio:1/1.12;object-fit:cover;border-radius:8px;background:var(--tint)}
.portrait-ph{
  width:100%;aspect-ratio:1/1.12;border-radius:8px;background:var(--tint);
  display:flex;align-items:center;justify-content:center;
  color:var(--ink-3);font-size:12px;letter-spacing:.08em;text-align:center;padding:0 14px;
}
.meta{margin-top:16px;font-size:14.5px;line-height:1.62;color:var(--ink-2)}
.meta h4{font-size:11.5px;letter-spacing:.12em;text-transform:uppercase;color:var(--ink-3);margin:16px 0 5px}
.meta .links{display:flex;flex-wrap:wrap;gap:8px}
.meta .links a{font-size:13px;padding:4px 10px;border:1px solid var(--rule);border-radius:999px;color:var(--ink-2)}
.meta .links a:hover{border-color:var(--ink-3);color:var(--ink);text-decoration:none}

/* ---------- headings ---------- */
.h2{font-size:13px;letter-spacing:.14em;text-transform:uppercase;color:var(--ink-3);margin-bottom:26px}
.sub{font-size:12px;letter-spacing:.1em;text-transform:uppercase;color:var(--ink-3);margin:26px 0 8px}
.sub:first-child{margin-top:0}

/* ---------- project cards ---------- */
.proj{display:grid;grid-template-columns:212px 1fr;gap:26px;padding:24px 0;align-items:start}
.proj+.proj{border-top:1px solid var(--rule)}
.proj img,.proj .ph,.proj .tile{width:212px;border-radius:6px;background:var(--tint)}
.proj img{height:auto;aspect-ratio:16/10;object-fit:cover}

/* typographic tile 鈥?used for papers that have no teaser figure.
   Deliberate design element, not a missing-image placeholder. */
.tile{
  aspect-ratio:16/10;background:var(--ink);color:#fff;
  display:flex;flex-direction:column;align-items:center;justify-content:center;
  gap:7px;padding:0 12px;text-align:center;
}
.tile .k{
  font:600 10px/1 ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  letter-spacing:.18em;text-transform:uppercase;opacity:.6;
}
.tile .b{font-size:19px;font-weight:600;line-height:1.15;letter-spacing:-.015em}
.ph{
  aspect-ratio:16/10;display:flex;align-items:center;justify-content:center;
  border:1px solid var(--rule);
  font:600 12px/1.4 ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  letter-spacing:.06em;color:var(--ink-3);text-align:center;padding:0 10px;
}
.proj .t{font-size:17px;font-weight:600;line-height:1.38;margin-bottom:6px}
.proj .a{font-size:14px;color:var(--ink-2);line-height:1.55}
.proj .a .me{font-weight:600;color:var(--ink)}
.venue{
  display:inline-block;margin-top:7px;font-size:12px;font-weight:600;
  letter-spacing:.06em;text-transform:uppercase;color:var(--ink);
  background:var(--tint);border-radius:4px;padding:2px 8px;
}
.venue.award{background:#fdf3d8;color:#7a5a00}
.proj .q{margin-top:9px;font-size:14.5px;font-style:italic;color:var(--ink-2)}
.proj .lk,.lk{margin-top:10px;display:flex;flex-wrap:wrap;gap:7px}
.lk a{font-size:12.5px;padding:2px 9px;border:1px solid var(--rule);border-radius:4px;color:var(--ink-2)}
.lk a:hover{border-color:var(--ink-3);color:var(--ink);text-decoration:none}
.more{margin-top:28px;font-size:15px;color:var(--ink-2)}

/* ---------- plain row lists ---------- */
.rows li{padding:9px 0;border-top:1px solid var(--rule);font-size:15.5px;line-height:1.62}
.rows li:first-child{border-top:none}
.rows .d{color:var(--ink-3);font-size:13.5px;display:block;margin-bottom:1px}
.tag{
  display:inline-block;font-size:11px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;
  color:#0a6b3d;background:#e6f4ec;border-radius:3px;padding:1px 6px;margin-right:7px;vertical-align:1.5px;
}
.note{
  margin:0 0 26px;padding:12px 16px;background:var(--tint);border-radius:6px;
  font-size:14.5px;color:var(--ink-2);
}

/* ---------- publications ---------- */
.yearbar{
  position:sticky;top:52px;z-index:40;background:rgba(255,255,255,.92);
  backdrop-filter:saturate(180%) blur(14px);-webkit-backdrop-filter:saturate(180%) blur(14px);
  border-bottom:1px solid var(--rule);padding:9px 0;
}
.yearbar .wrap{display:flex;flex-wrap:wrap;gap:5px}
.yearbar a{
  font:600 12.5px/1 ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
  padding:5px 9px;border-radius:4px;color:var(--ink-2);
}
.yearbar a:hover{background:var(--tint);color:var(--ink);text-decoration:none}
.yr{
  font-size:26px;font-weight:600;letter-spacing:-.02em;
  margin:44px 0 4px;padding-top:14px;border-top:2px solid var(--ink);
}
.yr:first-of-type{margin-top:8px}
.pub{
  display:grid;grid-template-columns:186px 1fr;gap:22px;align-items:start;
  padding:20px 0;border-top:1px solid var(--rule);
}
.pub>img{width:186px;aspect-ratio:16/10;object-fit:cover;border-radius:5px;background:var(--tint)}
.pub .t{font-size:16.5px;font-weight:600;line-height:1.42}
.note-sm{margin-top:4px;font-size:13px;color:var(--ink-3)}
.pub .a{margin-top:3px;font-size:14px;color:var(--ink-2);line-height:1.55}
.pub .a .me{font-weight:600;color:var(--ink)}
.pub .v{margin-top:4px;font-size:14px;font-style:italic;color:var(--ink-2)}
.pub .q{margin-top:8px;font-size:14px;line-height:1.65;color:var(--ink-2);
        border-left:2px solid var(--rule);padding-left:12px}

/* ---------- people grid ---------- */
.people{display:grid;grid-template-columns:repeat(auto-fill,minmax(146px,1fr));gap:26px 20px}
.person img,.person .ph2{width:100%;aspect-ratio:1/1.16;object-fit:cover;border-radius:7px;background:var(--tint)}
.person .ph2{
  border:1px solid var(--rule);display:flex;align-items:center;justify-content:center;
  color:var(--ink-3);font:600 22px/1 -apple-system,sans-serif;
}
.person .n{margin-top:9px;font-size:15px;font-weight:600;line-height:1.3}
.person .r{margin-top:2px;font-size:13px;color:var(--ink-2);line-height:1.45}
.person .y{margin-top:3px;font-size:12.5px;color:var(--ink-3);line-height:1.4}

/* ---------- affiliations ---------- */
.affil{display:flex;flex-wrap:wrap;gap:10px}
.affil a{font-size:13.5px;padding:7px 13px;border:1px solid var(--rule);border-radius:6px;color:var(--ink-2)}
.affil a:hover{border-color:var(--ink-3);color:var(--ink);text-decoration:none}

/* ---------- footer ---------- */
footer{border-top:1px solid var(--rule);padding:26px 0 46px;font-size:13.5px;color:var(--ink-3)}
footer .wrap{display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap}

/* ---------- responsive ---------- */
@media (max-width:760px){
  body{font-size:16px}
  section{padding:40px 0}
  .wrap{width:100%;padding:0 20px}
  .hero{padding-top:34px}
  .hero h1{font-size:32px}
  .phero h1{font-size:27px}
  .split{grid-template-columns:1fr;gap:30px}
  .card{max-width:190px}
  .proj{grid-template-columns:1fr;gap:14px}
  .proj img,.proj .ph,.proj .tile{width:100%;max-width:340px}
  .nav ul{gap:15px}
  .nav a{font-size:11.5px}
  .yearbar{top:52px}
  .pub{grid-template-columns:1fr;gap:12px}
  .pub>img{width:100%;max-width:340px}
  .people{grid-template-columns:repeat(auto-fill,minmax(118px,1fr));gap:20px 14px}
}

/* ---------- print ---------- */
@media print{
  .nav,.yearbar,footer{display:none}
  a{color:#000}
  .pub,.proj{break-inside:avoid}
}