/* ==========================================================================
   Xinyu Liang — personal site
   Navy hero and footer, cream paper body. Roboto Serif for headings,
   Roboto for text (same families as xinyu-liang.com).
   ========================================================================== */

:root{
  --navy:#0B1F3A;
  --navy-deep:#061527;
  --paper:#FAF7F1;
  --paper-alt:#FAF7F1;
  --ink:#14213A;
  --body:#2B313A;
  --muted:#5B6470;
  --line:#E3DDD2;
  --blue:#2573CC;
  --blue-ink:#1B57A0;
  --on-dark:#EFF2F5;
  --on-dark-mut:rgba(239,242,245,.74);
  --serif:"Roboto Serif",Georgia,"Times New Roman",serif;
  --sans:"Roboto",system-ui,-apple-system,"Segoe UI",Helvetica,Arial,sans-serif;
  --max:1080px;
  --gutter:20px;
}
@media (min-width:760px){:root{--gutter:40px}}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
html,body{margin:0;padding:0}
body{
  background:var(--paper);color:var(--body);
  font-family:var(--sans);font-size:16px;line-height:1.65;
  -webkit-font-smoothing:antialiased;overflow-x:hidden;
}
a{color:var(--blue-ink);text-decoration:none}
a:hover{text-decoration:underline;text-underline-offset:3px}
img{max-width:100%;display:block}
em{font-style:italic}
.wrap{max-width:var(--max);margin:0 auto;padding-left:var(--gutter);padding-right:var(--gutter)}

/* ---- Section label (About) ------------------------------------------- */
.label{
  font-family:var(--serif);font-size:clamp(21px,2.2vw,24px);font-weight:600;line-height:1.2;
  color:var(--ink);margin:0 0 10px;padding-top:12px;display:inline-block;position:relative;
}
.label::before{content:"";position:absolute;left:0;top:0;height:3px;width:100%;background:var(--blue);transform-origin:left;transform:scaleX(.35);transition:transform .7s cubic-bezier(.2,.7,.2,1) .15s}
.reveal.in .label::before{transform:scaleX(1)}

/* ---- Buttons ---------------------------------------------------------- */
.btn{
  display:inline-block;font-family:var(--sans);font-weight:500;font-size:14.5px;line-height:1;
  padding:11px 18px;border-radius:3px;border:1px solid transparent;transition:background .15s,color .15s,border-color .15s;
}
.btn:hover{text-decoration:none}
.btn-primary{background:var(--blue);color:#fff;border-color:var(--blue)}
.btn-primary:hover{background:var(--blue-ink);border-color:var(--blue-ink)}
.btn-ghost-dark{color:var(--on-dark);border-color:rgba(239,242,245,.55)}
.btn-ghost-dark:hover{border-color:var(--on-dark);background:rgba(239,242,245,.08)}
.btn-ghost{color:var(--ink);border-color:var(--ink)}
.btn-ghost:hover{background:var(--ink);color:#fff}

/* ---- Nav -------------------------------------------------------------- */
.nav{
  position:sticky;top:0;z-index:20;background:rgba(244,240,232,.94);backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);
}
.nav .wrap{display:flex;align-items:center;justify-content:space-between;height:56px;gap:16px}
.brand{color:var(--ink);font-family:var(--serif);font-weight:600;font-size:18px}
.brand:hover{text-decoration:none}
.nav-links{display:flex;align-items:center;gap:26px;font-size:14px;font-weight:500}
.nav-links a{color:var(--body);padding-bottom:2px;border-bottom:2px solid transparent}
.nav-links a:hover{color:var(--ink);text-decoration:none}
.nav-links a.active{color:var(--ink);border-bottom-color:var(--blue)}

/* ---- Hero (navy) ------------------------------------------------------ */
.hero{
  position:relative;overflow:hidden;color:var(--on-dark);
  background:
    radial-gradient(900px 520px at 78% 30%, rgba(37,115,204,.28), transparent 60%),
    radial-gradient(700px 420px at 8% 90%, rgba(37,115,204,.14), transparent 60%),
    var(--navy);
}
.hero::before{
  content:"";position:absolute;inset:0;pointer-events:none;opacity:.35;
  background-image:repeating-linear-gradient(135deg, rgba(239,242,245,.05) 0 1px, transparent 1px 22px);
}
.hero .wrap{position:relative}
.hero .wrap{display:grid;gap:28px;padding-top:40px;padding-bottom:40px;align-items:center}
@media (min-width:860px){
  .hero .wrap{grid-template-columns:1.2fr .8fr;gap:56px;padding-top:56px;padding-bottom:56px}
}
@keyframes rise{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}
.hero h1,.hero .role,.hero .pron,.hero .lede,.hero .cta,.profile-links,.hero-photo{animation:rise .7s cubic-bezier(.2,.7,.2,1) both}
.profile-links{animation-delay:.44s}
.hero .role{animation-delay:.08s}.hero .pron{animation-delay:.14s}.hero .lede{animation-delay:.2s}.hero .lede+.lede{animation-delay:.28s}.hero .cta{animation-delay:.36s}.hero-photo{animation-delay:.2s}
@media (prefers-reduced-motion:reduce){.hero h1,.hero .role,.hero .pron,.hero .lede,.hero .cta,.hero-photo{animation:none}}
.hero h1{
  font-family:var(--serif);font-weight:600;font-size:clamp(32px,3.6vw,42px);line-height:1.05;letter-spacing:-.02em;
  margin:0 0 12px;color:var(--on-dark);
}
.hero .role{
  font-family:var(--serif);font-size:clamp(16.5px,1.7vw,18.5px);font-weight:400;line-height:1.35;
  color:var(--on-dark);margin:0 0 6px;
}
.pron{font-family:var(--sans);font-size:13px;color:var(--on-dark-mut);margin:0 0 20px}
.hero .lede{
  font-family:var(--serif);font-size:clamp(16.5px,1.8vw,18px);line-height:1.5;
  color:var(--on-dark);max-width:50ch;margin:0 0 14px;
}
.hero .lede+.lede{margin-bottom:24px}
.hero .lede strong{font-weight:600}
.hero .cta{display:flex;flex-wrap:wrap;gap:12px}
.profile-links{display:flex;flex-wrap:wrap;gap:8px 24px;margin-top:16px}
.profile-links a{display:inline-flex;align-items:center;gap:7px;font-family:var(--sans);font-size:14px;font-weight:500;color:var(--on-dark-mut);transition:color .15s}
.profile-links a:hover{color:var(--on-dark);text-decoration:none}
.profile-links svg{width:16px;height:16px}
.profile-links svg *{stroke:currentColor;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round;fill:none}
.hero-photo{
  position:relative;margin:0;aspect-ratio:4/5;max-width:340px;width:100%;justify-self:end;
  background:var(--navy-deep);border:1px solid rgba(239,242,245,.18);
  box-shadow:0 24px 60px rgba(0,0,0,.35);
}
.hero-photo::before{
  content:"";position:absolute;inset:0;transform:translate(14px,14px);z-index:-1;
  border:2px solid var(--blue);opacity:.9;
}
.hero-photo img{width:100%;height:100%;object-fit:cover}
@media (max-width:859px){.hero-photo{max-width:320px;justify-self:start}}

/* ---- Reveal on scroll ------------------------------------------------- */
.reveal{opacity:0;transform:translateY(16px);transition:opacity .6s ease,transform .6s cubic-bezier(.2,.7,.2,1)}
.reveal.in{opacity:1;transform:none}
@media (prefers-reduced-motion:reduce){.reveal{opacity:1;transform:none;transition:none}}

/* ---- Sections --------------------------------------------------------- */
.section{padding:48px 0}
@media (min-width:860px){.section{padding:64px 0}}
.section.alt{background:var(--paper-alt)}
#research{background:#FAF7F1;border-top:1px solid #D8D1C4;box-shadow:inset 0 1px 0 #fff}
#collaboration{border-top:1px solid #D8D1C4}
.section h2{
  font-family:var(--serif);font-weight:500;font-size:clamp(24px,2.8vw,30px);line-height:1.2;letter-spacing:-.01em;
  color:var(--ink);margin:0 0 18px;max-width:30ch;
}

/* About */
.about-grid{max-width:70ch}
.about-grid p{margin:0 0 12px;font-family:var(--serif);font-size:16px;line-height:1.65}
.about-grid p:last-child{margin-bottom:0}
.about-links{margin-top:30px;display:flex;flex-wrap:wrap;gap:12px 26px;align-items:center}
.arrow{font-family:var(--sans);font-size:16px;font-weight:500;color:var(--blue-ink);text-decoration:underline;text-underline-offset:4px;text-decoration-color:rgba(27,87,160,.35)}
.arrow:hover{text-decoration-color:var(--blue-ink)}

/* Research heading + framing sentence */
.statement{
  font-family:var(--serif);font-size:clamp(16.5px,1.7vw,18.5px);line-height:1.45;color:var(--ink);
  margin:0 0 36px;
}

/* Research areas */
.threads{display:grid;gap:18px;margin:0 0 32px}
@media (min-width:760px){.threads{grid-template-columns:repeat(3,1fr);gap:28px}}
.thread{border-top:1px solid var(--ink);padding-top:10px;transition:border-color .2s,transform .2s}
.thread:hover{border-top-color:var(--blue);transform:translateY(-2px)}
.thread:hover h3{color:var(--blue-ink)}
.thread h3{font-family:var(--serif);font-weight:600;font-size:16px;line-height:1.3;color:var(--ink);margin:0 0 5px;transition:color .2s}
@media (min-width:760px){.thread h3{min-height:1.3em}}
.thread p{margin:0;font-family:var(--serif);font-size:14.5px;line-height:1.55;color:var(--body)}

/* ---- Publications: group heading in a left column, papers on the right --- */
.paper-group{display:grid;gap:16px;margin-top:40px}
@media (min-width:860px){.paper-group{grid-template-columns:200px minmax(0,1fr);gap:48px;margin-top:48px}}
.group-heading{border-top:1px solid var(--ink);padding-top:16px}
.group-heading h3{font-family:var(--serif);font-weight:500;font-size:20px;line-height:1.3;color:var(--ink);margin:0}
.group-note{display:block;font-family:var(--serif);font-size:15px;font-weight:400;font-style:italic;color:var(--muted);margin-top:3px}
.publication{position:relative;border-top:1px solid var(--line);padding:18px 0 16px}
.publication:first-child{border-top:1px solid var(--ink)}
.publication::before{content:"";position:absolute;left:-18px;top:14px;bottom:14px;width:3px;background:var(--blue);opacity:0;transition:opacity .2s}
.publication:hover::before{opacity:1}
.pub-title{font-family:var(--serif);font-weight:500;font-size:17.5px;line-height:1.4;color:var(--ink);margin:0;max-width:64ch}
.pub-authors{margin:6px 0 0;font-family:var(--serif);font-size:15px;line-height:1.55;color:var(--body)}
.pub-authors strong{font-weight:600;color:var(--ink)}
.pub-status{margin:3px 0 0;font-family:var(--serif);font-size:15px;line-height:1.55;color:var(--ink)}
.nowrap{white-space:nowrap}
.pub-links{float:left;margin:0 20px 0 0;padding:6px 0 2px;font-family:var(--serif);font-size:15px;font-weight:400}
.pub-link{display:inline-flex;align-items:center;gap:5px;color:var(--blue-ink);white-space:nowrap}
.pub-link:hover{text-decoration:underline;text-underline-offset:3px}
.pub-link svg{width:12px;height:12px;display:block}
.pub-link svg path{stroke:currentColor;stroke-width:1.8;stroke-linecap:round;stroke-linejoin:round}
.publication::after{content:"";display:block;clear:both}
details>summary{list-style:none;cursor:pointer;display:inline-flex;align-items:center;gap:6px;width:fit-content;font-family:var(--serif);font-size:15px;color:var(--blue-ink);padding:6px 0 2px}
details>summary::-webkit-details-marker{display:none}
details>summary::marker{content:""}
details>summary:hover{text-decoration:underline;text-underline-offset:3px}
.chev{width:13px;height:13px;transition:transform .15s}
.chev path{stroke:currentColor;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round}
details[open]>summary .chev{transform:rotate(180deg)}
.when-open,details[open]>summary .when-closed{display:none}
details[open]>summary .when-open{display:inline}
.author-details{margin-top:4px}
.author-details>summary{font-family:var(--serif);font-size:15px;color:var(--muted);padding-top:2px}
.author-details .pub-authors{margin:4px 0 2px}
.pub-meta{clear:both;margin:8px 0 4px 2px;padding:2px 0 2px 14px;border-left:2px solid var(--line);display:grid;gap:3px}
.pub-meta div{display:grid;grid-template-columns:180px 1fr;gap:16px;align-items:baseline}
.pub-meta dt{font-family:var(--serif);font-size:15px;font-weight:400;color:var(--muted);margin:0}
.pub-meta dd{margin:0;font-family:var(--serif);font-size:15px;line-height:1.55;color:var(--body)}
.pub-meta dd a{color:var(--blue-ink);white-space:nowrap;background:linear-gradient(var(--blue-ink),var(--blue-ink)) no-repeat 0 100%/0 1px;transition:background-size .25s}
.pub-meta dd a:hover{background-size:100% 1px;text-decoration:none}
@media (max-width:560px){.pub-meta div{grid-template-columns:1fr;gap:2px}}
.after-list{margin-top:24px;display:flex;flex-wrap:wrap;align-items:center;gap:14px 18px}
.after-list .note{font-size:15px;color:var(--muted)}

/* ---- Research Collaboration ------------------------------------------- */
.collab{display:grid;gap:22px;align-items:start}
@media (min-width:860px){.collab{grid-template-columns:minmax(0,1fr) auto;gap:56px;align-items:center}}
.collab-text{margin:0;max-width:64ch;font-family:var(--serif);font-size:16px;line-height:1.65;color:var(--body)}
.collab-actions{display:flex;flex-direction:column;align-items:flex-start;gap:8px}

/* ---- Research page header -------------------------------------------- */
.page-head{padding:40px 0 4px}
@media (min-width:860px){.page-head{padding:48px 0 8px}}
.page-head h1{padding-bottom:12px;border-bottom:1px solid var(--ink);
  font-family:var(--serif);font-weight:500;font-size:clamp(28px,3.4vw,36px);line-height:1.1;letter-spacing:-.01em;
  color:var(--ink);margin:0 0 8px;
}
.page-head .intro{margin:0;font-size:17.5px;color:var(--body);max-width:62ch}
.pub-section{padding:24px 0 12px}
.pub-section:last-of-type{padding-bottom:56px}
.pub-section h2{
  font-family:var(--serif);font-weight:500;font-size:23px;line-height:1.2;color:var(--ink);
  margin:0 0 4px;padding-bottom:10px;border-bottom:1px solid var(--ink);
}

/* ---- Footer (navy) ---------------------------------------------------- */
.footer{background:var(--navy);color:var(--on-dark);padding:32px 0 28px;border-top:3px solid transparent;border-image:linear-gradient(90deg,var(--blue),transparent 70%) 1}
.footer .brand{color:var(--on-dark)}
.footer .tagline{font-family:var(--serif);font-size:15px;color:var(--on-dark-mut);margin:8px 0 12px}
.footer .small{font-family:var(--sans);font-size:13px;color:var(--on-dark-mut);margin:0;display:flex;flex-wrap:wrap;gap:6px 18px}
.footer .small a{color:var(--on-dark);text-decoration:underline;text-underline-offset:3px;text-decoration-color:rgba(239,242,245,.4)}

/* ---- Floating bar (appears after the top of the page scrolls away) ---- */
.follow{
  position:fixed;left:0;right:0;bottom:0;z-index:15;
  background:rgba(11,31,58,.96);color:var(--on-dark);border-top:1px solid rgba(239,242,245,.12);
  transform:translateY(100%);transition:transform .25s;
}
.follow.show{transform:none}
.follow .wrap{display:flex;align-items:center;justify-content:space-between;gap:16px;height:52px}
.follow-name{margin:0;font-family:var(--serif);font-weight:600;font-size:14px;color:var(--on-dark);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.follow-name span{font-family:var(--sans);font-weight:400;font-size:12.5px;color:var(--on-dark-mut);margin-left:10px}
.follow-links{margin:0;display:flex;align-items:center;gap:18px;font-family:var(--sans);font-size:13.5px;white-space:nowrap}
.follow-links a{color:var(--on-dark);display:inline-flex;align-items:center;gap:6px}
.follow-links svg{width:15px;height:15px}
.follow-links svg *{stroke:currentColor;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round;fill:none}
.follow-main{
  font-weight:500;font-size:13.5px;line-height:1;padding:9px 14px;border-radius:3px;background:var(--blue);color:#fff !important;
}
.follow-main:hover{background:var(--blue-ink);text-decoration:none}

@media (max-width:859px){.follow{display:none}}