/* Chen Gao — site styles. Space Grotesk (display + UI) + Spectral (body), white, CV-red accent. */
:root{
  --bg:#ffffff;
  --ink:#16181d;
  --text:#2a2f38;
  --muted:#4f5763;
  --red:#94070a;
  --red-2:#7a0608;
  --tint:rgba(148,7,10,.06);
  --line:rgba(22,24,29,.12);
  --line-2:rgba(22,24,29,.22);
  --body:'Spectral',Georgia,'Times New Roman',serif;
  --sans:'Space Grotesk',-apple-system,BlinkMacSystemFont,'Segoe UI','Helvetica Neue',system-ui,sans-serif;
  --maxw:1080px;
  --pad:40px;
  --ease:cubic-bezier(.2,.6,.2,1);
}
*{box-sizing:border-box;margin:0;padding:0}
html{-webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;scroll-behavior:smooth}
body{background:var(--bg);color:var(--ink);font-family:var(--body);font-size:18px;line-height:1.6}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
em{font-style:italic}
::selection{background:var(--red);color:#fff}
a:focus-visible,summary:focus-visible,.btn:focus-visible{outline:2px solid var(--red);outline-offset:3px;border-radius:2px}

/* shell */
.page{min-height:100vh;display:flex;flex-direction:column}
.wrap{max-width:var(--maxw);width:100%;margin:0 auto;padding-left:var(--pad);padding-right:var(--pad)}
main{flex:1}
.divider{height:1px;background:var(--line)}

/* header */
.site-header{padding-top:34px}
.site-header .bar{display:flex;align-items:baseline;justify-content:space-between;gap:24px;flex-wrap:wrap}
.wordmark{font-family:var(--sans);font-size:20px;font-weight:600;letter-spacing:-.02em;color:var(--ink);transition:color .18s var(--ease)}
.wordmark:hover{color:var(--red)}
.nav{display:flex;flex-wrap:wrap;gap:30px;row-gap:8px;align-items:baseline;font-family:var(--sans);font-size:16px;font-weight:500;letter-spacing:.01em}
.nav a{color:var(--muted);padding-bottom:4px;border-bottom:1.5px solid transparent;transition:color .18s var(--ease),border-color .18s var(--ease)}
.nav a:hover{color:var(--ink)}
.nav a[aria-current=page]{color:var(--ink);border-bottom-color:var(--red)}
.head-rule{height:1px;background:var(--line);margin-top:22px}

/* sans micro-type */
.eyebrow{font-family:var(--sans);font-size:15px;font-weight:600;letter-spacing:.18em;text-transform:uppercase;color:var(--red);margin-bottom:14px}
.kicker{font-family:var(--sans);font-size:14.5px;font-weight:600;letter-spacing:.13em;text-transform:uppercase;color:var(--red)}
.meta{font-family:var(--sans);font-size:15.5px;letter-spacing:.01em;color:var(--muted)}
.byline{font-family:var(--sans);font-size:17px;color:var(--muted)}
.side-label{font-family:var(--sans);font-size:15px;font-weight:600;letter-spacing:.15em;text-transform:uppercase;color:var(--ink)}

/* headings (Space Grotesk) */
h1.name{font-family:var(--sans);font-weight:700;font-size:clamp(46px,6vw,68px);line-height:1;letter-spacing:-.03em}
h1.page-title{font-family:var(--sans);font-weight:700;font-size:clamp(38px,4.6vw,54px);line-height:1.05;letter-spacing:-.025em}
h2.title{font-family:var(--sans);font-weight:600;font-size:28px;line-height:1.22;letter-spacing:-.015em;margin-bottom:10px}
h2.title.sm{font-size:24px;line-height:1.28;margin-bottom:14px}
.zh{font-family:'Noto Serif SC',var(--body);font-size:36px;color:var(--ink);font-weight:500;letter-spacing:.08em;margin-top:3px}

/* red accent bar */
.accent-bar{width:54px;height:4px;background:var(--red);border-radius:2px;transform-origin:left center;margin:24px 0}

/* prose + links */
.prose p{font-size:19px;line-height:1.66;color:var(--text)}
.prose p+p{margin-top:20px}
.lead{font-size:20px!important;line-height:1.6!important;color:var(--ink)!important}
a.link{color:var(--ink);border-bottom:1px solid var(--line-2);transition:color .18s var(--ease),border-color .18s var(--ease)}
a.link:hover{color:var(--red);border-bottom-color:var(--red)}
a.accent{color:var(--red);border-bottom:1px solid rgba(148,7,10,.35);transition:border-color .18s var(--ease)}
a.accent:hover{border-bottom-color:var(--red)}

/* buttons — underline links (faint resting rule, red on hover) */
.btn-row{display:flex;gap:30px;flex-wrap:wrap;align-items:center;margin-top:30px}
.btn{font-family:var(--sans);font-weight:500;font-size:16px;letter-spacing:.01em;position:relative;display:inline-block;color:var(--ink);padding:8px 0;background:none;border:0;transition:color .18s var(--ease)}
.btn::after{content:'';position:absolute;left:0;bottom:4px;width:100%;height:1px;background:var(--line-2);transition:background-color .18s var(--ease),height .18s var(--ease)}
.btn:hover{color:var(--red)}
.btn:hover::after{background:var(--red);height:2px}
.btn-primary{color:var(--red)}
.btn-primary::after{background:var(--red);height:2px}
.btn-primary:hover{color:var(--red-2)}
.btn-sm{font-size:15px}

/* hero */
.hero{display:grid;grid-template-columns:1fr 320px;gap:64px;align-items:start;padding:60px 0 58px}
.hero .intro{max-width:600px}
.portrait{position:relative}
.portrait img{width:100%;border-radius:2px;border:1px solid var(--line-2);filter:grayscale(.12) contrast(1.02);transition:transform .4s var(--ease),box-shadow .4s var(--ease)}
.portrait:hover img{transform:translateY(-2px);box-shadow:0 14px 32px rgba(22,24,29,.12)}
.portrait .tag{font-family:var(--sans);font-size:14.5px;letter-spacing:.01em;color:var(--muted);margin-top:12px}

/* two-column rows (label left, body right) */
.row{display:grid;grid-template-columns:200px 1fr;gap:40px;padding:48px 0}
.row .body{max-width:700px}
.aside .meta{margin-top:4px}

/* news / education items */
.item{padding:22px 0;border-bottom:1px solid var(--line)}
.item:first-child{padding-top:0}
.item:last-child{border-bottom:0;padding-bottom:0}
.news-item{display:flex;gap:24px}
.news-item .when{flex:0 0 116px;font-family:var(--sans);font-size:15px;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--red);padding-top:5px}
.news-item p{font-size:19px;line-height:1.55}
.degree{font-size:20px;line-height:1.4;color:var(--ink)}
.degree .q{color:var(--muted)}
.item .meta{margin-top:5px}
.note-ref{font-family:var(--sans);font-size:16px;color:var(--muted);margin-top:24px}

/* abstract details */
details.abstract{margin-bottom:24px}
details.abstract summary{display:flex;align-items:center;gap:10px;cursor:pointer;padding:4px 0;margin-bottom:12px;list-style:none}
details.abstract summary::-webkit-details-marker{display:none}
.ab-label{font-family:var(--sans);font-size:15px;font-weight:600;letter-spacing:.13em;text-transform:uppercase;color:var(--ink)}
.ab-caret{color:var(--red);font-size:13px;line-height:1;transition:transform .2s ease}
details.abstract[open] .ab-caret{transform:rotate(90deg)}
.ab-state{font-family:var(--sans);font-size:14px;letter-spacing:.05em;text-transform:uppercase;color:var(--muted);margin-left:auto}
.ab-state::after{content:'Show'}
details.abstract[open] .ab-state::after{content:'Hide'}

/* award callout */
.callout{padding:16px 20px;background:var(--tint);border-left:2px solid var(--red);border-radius:2px}
.callout p{font-size:17px;line-height:1.5;color:var(--text)}

/* link lists (notes / code) */
.linklist{display:flex;flex-direction:column;gap:28px}
.linklist .entry{padding-bottom:26px;border-bottom:1px solid var(--line)}
.linklist .entry:last-child{padding-bottom:0;border-bottom:0}
.entry-title{font-family:var(--sans);font-weight:500;font-size:21px;letter-spacing:-.01em;color:var(--ink);border-bottom:1px solid var(--line-2);display:inline-block;margin-bottom:8px;transition:color .18s var(--ease),border-color .18s var(--ease)}
.entry-title:hover{color:var(--red);border-bottom-color:var(--red)}
.linklist .entry p{font-size:18px;line-height:1.55;color:var(--muted)}

/* task bullets (teaching) */
.tasks{list-style:none;display:flex;flex-direction:column;gap:10px;margin-top:4px}
.tasks li{font-size:18px;line-height:1.55;color:var(--text);display:flex;gap:14px}
.tasks li::before{content:'';flex:none;width:6px;height:6px;border-radius:50%;background:var(--red);margin-top:11px}

/* footer */
.site-footer{border-top:1px solid var(--line);margin-top:8px}
.site-footer .bar{display:flex;justify-content:space-between;flex-wrap:wrap;gap:12px;padding-top:24px;padding-bottom:24px;font-family:var(--sans);font-size:15px;color:var(--muted)}
.site-footer a{color:var(--ink);border-bottom:1px solid var(--line-2);transition:color .18s var(--ease),border-color .18s var(--ease)}
.site-footer a:hover{color:var(--red);border-bottom-color:var(--red)}

/* page head (interior pages) */
.page-head{padding:58px 0 0}
.page-head + .divider{margin-top:36px}
.page-head .eyebrow{position:relative}
.page-head .eyebrow::after{content:'';display:block;width:54px;height:4px;border-radius:2px;background:var(--red);margin:16px 0 2px}

/* animations */
@keyframes riseIn{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}
@keyframes barGrow{from{transform:scaleX(0)}to{transform:scaleX(1)}}
.reveal{animation:riseIn .65s var(--ease) both}
.reveal-1{animation-delay:.04s}
.reveal-2{animation-delay:.13s}
.reveal-3{animation-delay:.22s}
.reveal-4{animation-delay:.31s}
.accent-bar{animation:barGrow .7s var(--ease) .22s both}

@media (prefers-reduced-motion:reduce){
  *{animation:none!important;transition:none!important;scroll-behavior:auto!important}
}

/* responsive */
@media (max-width:760px){
  :root{--pad:22px}
  body{font-size:17px}
  .hero{grid-template-columns:1fr;gap:30px;padding:38px 0 42px}
  .hero .intro{max-width:none}
  .page-head{padding:36px 0 0}
  .portrait{max-width:340px}
  .row{grid-template-columns:1fr;gap:16px;padding:36px 0}
  .news-item{flex-direction:column;gap:6px}
  .news-item .when{padding-top:0}
  .nav{gap:18px;row-gap:6px;font-size:15px}
  .accent-bar{margin:20px 0}
}