/* Xufei Liu — academic site stylesheet */
:root {
  --ink: #1a1a1a;
  --muted: #555;
  --accent: #011F5B;      /* Penn blue */
  --accent-2: #990000;    /* Penn red, used sparingly */
  --rule: #e2e2e2;
  --bg: #ffffff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: Georgia, 'Times New Roman', serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.55;
  font-size: 17px;
}

.container { max-width: 880px; margin: 0 auto; padding: 0 22px; }

/* ---------- navigation ---------- */
nav {
  border-bottom: 1px solid var(--rule);
  background: var(--bg);
}
nav .container {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 22px;
  padding-top: 18px;
  padding-bottom: 14px;
}
nav .brand {
  font-size: 20px;
  font-weight: bold;
  color: var(--accent);
  text-decoration: none;
  margin-right: auto;
}
nav a.navlink {
  color: var(--muted);
  text-decoration: none;
  font-size: 15.5px;
  font-family: 'Helvetica Neue', Arial, sans-serif;
  letter-spacing: 0.02em;
}
nav a.navlink:hover { color: var(--accent-2); }
nav a.navlink.active { color: var(--ink); border-bottom: 2px solid var(--accent-2); padding-bottom: 2px; }

/* ---------- headings & text ---------- */
h1 { font-size: 30px; margin: 26px 0 4px; color: var(--ink); }
h2 {
  font-size: 21px;
  margin: 34px 0 12px;
  color: var(--accent);
  border-bottom: 1px solid var(--rule);
  padding-bottom: 5px;
}
h3 { font-size: 17.5px; margin: 22px 0 2px; }
.subtitle { color: var(--muted); margin: 0 0 2px; }
.jobmarket {
  font-weight: bold;
  background: #fdf6ec;
  border-left: 4px solid var(--accent-2);
  padding: 9px 14px;
  margin: 18px 0;
}
a { color: var(--accent); }
a:hover { color: var(--accent-2); }

/* ---------- home layout ---------- */
.profile {
  display: flex;
  gap: 34px;
  margin-top: 34px;
  align-items: flex-start;
}
.profile img {
  width: 235px;
  border-radius: 6px;
  flex-shrink: 0;
}
.contact { color: var(--muted); font-size: 15.5px; margin-top: 10px; }
.contact div { margin: 2px 0; }

/* ---------- research entries ---------- */
.paper { margin-bottom: 26px; }
.paper .title { font-weight: bold; font-size: 17.5px; }
.paper .byline { font-style: italic; color: var(--muted); margin: 2px 0; }
.paper .status { font-size: 15.5px; color: var(--muted); margin: 2px 0; }
.paper .tag {
  font-style: normal;
  color: var(--accent-2);
  font-weight: bold;
}
details { margin-top: 6px; }
details summary {
  cursor: pointer;
  color: var(--accent);
  font-size: 15.5px;
  font-family: 'Helvetica Neue', Arial, sans-serif;
}
details p { font-size: 15.5px; margin: 8px 0 0; color: #333; }

/* ---------- lists & tables ---------- */
ul { padding-left: 22px; }
li { margin-bottom: 8px; }
.talk-year { color: var(--muted); }

/* ---------- footer ---------- */
footer {
  border-top: 1px solid var(--rule);
  margin-top: 60px;
  padding: 18px 0 34px;
  color: var(--muted);
  font-size: 14px;
}

/* ---------- mobile ---------- */
@media (max-width: 640px) {
  .profile { flex-direction: column; align-items: center; text-align: center; }
  .profile img { width: 200px; }
  .contact { text-align: center; }
  nav .container { gap: 4px 14px; }
  body { font-size: 16px; }
}