/* =========================================================================
   Siyi Li — academic personal website
   One stylesheet, no frameworks, no build step.
   Change the values in :root below to restyle the whole site.
   ========================================================================= */

:root {
  --ink:        #1a1c1e;   /* body text            */
  --ink-soft:   #5b6168;   /* meta / secondary text */
  --accent:     #7a1c22;   /* links, rules — Rochester dandelion-adjacent maroon */
  --accent-lit: #a3313a;
  --bg:         #ffffff;
  --bg-soft:    #f7f6f4;   /* card / featured background */
  --line:       #e2e0dc;
  --maxw:       780px;     /* text column width */
  --serif:      "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, serif;
  --sans:       -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Helvetica, Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink:      #e8e6e3;
    --ink-soft: #a2a6ab;
    --accent:   #e79aa0;
    --accent-lit: #f3b8bd;
    --bg:       #16181a;
    --bg-soft:  #202326;
    --line:     #33383c;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 72px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; border-bottom: 1px solid rgba(122,28,34,.28); }
a:hover { color: var(--accent-lit); border-bottom-color: currentColor; }
@media (prefers-color-scheme: dark) { a { border-bottom-color: rgba(231,154,160,.35); } }

/* ---------- nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 12px 24px;
  display: flex; align-items: center; justify-content: space-between; gap: 20px;
  flex-wrap: wrap;
}
.nav-brand {
  font-family: var(--serif); font-size: 1.05rem; font-weight: 600;
  color: var(--ink); border: none; letter-spacing: .01em;
}
.nav-links { list-style: none; display: flex; gap: 18px; margin: 0; padding: 0; flex-wrap: wrap; }
.nav-links a {
  font-size: .875rem; color: var(--ink-soft); border: none;
  padding-bottom: 2px; border-bottom: 1px solid transparent;
}
.nav-links a:hover { color: var(--accent); border-bottom-color: var(--accent); }

/* ---------- layout ---------- */
main { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

section { padding: 48px 0; border-top: 1px solid var(--line); }
section:first-of-type { border-top: none; }

h2 {
  font-family: var(--serif);
  font-size: 1.5rem; font-weight: 600; letter-spacing: .01em;
  margin: 0 0 22px;
}
h3.subhead {
  font-family: var(--sans);
  font-size: .78rem; font-weight: 700; text-transform: uppercase; letter-spacing: .12em;
  color: var(--ink-soft);
  margin: 40px 0 16px;
}
h3.subhead:first-of-type { margin-top: 8px; }

/* ---------- hero ---------- */
.hero {
  display: flex; gap: 34px; align-items: flex-start;
  padding: 56px 0 8px;
}
.hero-photo {
  width: 168px; height: 168px; flex: none;
  border-radius: 6px; object-fit: cover;
  border: 1px solid var(--line);
}
.hero-text { flex: 1 1 auto; min-width: 0; }
.hero h1 {
  font-family: var(--serif);
  font-size: 2.1rem; font-weight: 600; letter-spacing: -.01em;
  margin: 0 0 8px; line-height: 1.15;
}
.hero-role { margin: 0 0 14px; color: var(--ink-soft); font-size: 1.02rem; line-height: 1.5; }
.badge {
  display: inline-block; margin: 0 0 16px;
  font-size: .78rem; font-weight: 600; letter-spacing: .04em;
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 9%, transparent);
  border: 1px solid color-mix(in srgb, var(--accent) 26%, transparent);
  border-radius: 999px; padding: 4px 13px;
}
.hero-fields { font-size: .93rem; color: var(--ink-soft); margin: 0 0 20px; }
.hero-fields strong { color: var(--ink); }

/* ---------- buttons ---------- */
.hero-actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 0; }
.btn {
  display: inline-block; border: 1px solid var(--line); border-radius: 5px;
  padding: 7px 15px; font-size: .875rem; color: var(--ink); background: var(--bg);
  transition: border-color .15s, color .15s;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-lit); border-color: var(--accent-lit); color: #fff; }
@media (prefers-color-scheme: dark) { .btn-primary, .btn-primary:hover { color: #1a1013; } }

/* ---------- papers ---------- */
.paper { margin: 0 0 30px; }
.paper:last-child { margin-bottom: 0; }
.paper h3, .paper h4 {
  font-family: var(--serif);
  font-size: 1.12rem; font-weight: 600; line-height: 1.35;
  margin: 0 0 5px;
}
.paper h4 { font-size: 1.05rem; }
.paper-meta {
  font-size: .8rem; color: var(--ink-soft);
  letter-spacing: .03em; margin: 0 0 10px;
}
.paper-featured {
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 5px;
  padding: 24px 26px;
}
.abstract { margin: 0 0 12px; font-size: .95rem; text-align: justify; hyphens: auto; }
.keywords { font-size: .85rem; color: var(--ink-soft); margin: 10px 0 0; }
.paper-links { margin: 12px 0 0; display: flex; flex-wrap: wrap; gap: 18px; font-size: .9rem; }

details { margin: 6px 0 0; }
details summary {
  cursor: pointer; font-size: .85rem; color: var(--accent);
  list-style: none; display: inline-flex; align-items: center; gap: 6px;
  user-select: none;
}
details summary::-webkit-details-marker { display: none; }
details summary::before { content: "▸"; font-size: .8em; transition: transform .15s; }
details[open] summary::before { transform: rotate(90deg); }
details[open] summary { margin-bottom: 10px; }

/* ---------- references ---------- */
.refs { padding-left: 20px; font-size: .95rem; }
.refs li { margin-bottom: 8px; }

.muted { color: var(--ink-soft); font-size: .95rem; }

/* ---------- footer ---------- */
footer {
  max-width: var(--maxw); margin: 0 auto; padding: 32px 24px 56px;
  border-top: 1px solid var(--line);
  font-size: .82rem; color: var(--ink-soft);
}
footer p { margin: 0; }

/* ---------- mobile ---------- */
@media (max-width: 640px) {
  body { font-size: 16px; }
  .hero { flex-direction: column; gap: 22px; padding-top: 36px; }
  .hero-photo { width: 132px; height: 132px; }
  .hero h1 { font-size: 1.8rem; }
  .nav-inner { padding: 10px 20px; gap: 10px; }
  .nav-links { gap: 14px; }
  .paper-featured { padding: 20px; }
  .abstract { text-align: left; }
  main, footer { padding-left: 20px; padding-right: 20px; }
}

/* ---------- print ---------- */
@media print {
  .nav { display: none; }
  details { display: block; }
  details > *:not(summary) { display: block !important; }
  a { color: var(--ink); border: none; }
}