/* Lu Lab (陆伟实验室) — restrained academic style
   White background, hairline borders, one muted vermilion accent. */

:root {
  --text: #212121;
  --muted: #666666;
  --accent: #a03b2a;
  --line: #e4e0d8;
  --paper: #ffffff;
  --wash: #f7f5f1;
  --serif: "Noto Serif SC", "Songti SC", "SimSun", serif;
  --sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", -apple-system, sans-serif;
  --maxw: 1024px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--sans);
  color: var(--text);
  background: var(--paper);
  line-height: 1.75;
  font-size: 16px;
}

/* Language toggle: exactly one of .lang-zh / .lang-en is visible */
html[lang="zh-CN"] .lang-en { display: none; }
html[lang="en"] .lang-zh { display: none; }

.container { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

/* ---------- Header ---------- */
.site-header {
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}
.site-header .container {
  display: flex; align-items: center; justify-content: space-between; gap: 40px;
  padding-top: 12px; padding-bottom: 12px;
}
.brand { display: flex; flex-direction: column; gap: 2px; text-decoration: none; color: var(--text); flex-shrink: 1; }
.brand-name {
  font-family: var(--serif); font-size: 1.2rem; font-weight: 700;
  letter-spacing: 0.03em;
}
.brand-sub { font-size: 0.9rem; color: var(--muted); margin-left: 10px; }
.brand-tag { font-size: 0.78rem; color: var(--muted); max-width: 290px; line-height: 1.4; }

.site-nav { display: flex; align-items: baseline; gap: 0; flex-wrap: nowrap; flex-shrink: 0; }
.site-nav a {
  text-decoration: none; color: var(--text);
  padding: 4px 8px;
  font-size: 0.9rem;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
}
.site-nav a:hover { color: var(--accent); }
.site-nav a.active { color: var(--accent); border-bottom-color: var(--accent); }

.lang-toggle {
  margin-left: 10px;
  border: none; background: none;
  color: var(--muted);
  font-size: 0.9rem; padding: 4px 2px; cursor: pointer;
  text-decoration: underline;
  white-space: nowrap;
  flex-shrink: 0;
}
.lang-toggle:hover { color: var(--accent); }

.nav-hamburger {
  display: none;
  background: none; border: none; cursor: pointer;
  font-size: 1.4rem; color: var(--text); padding: 4px 8px;
}

@media (max-width: 940px) {
  .site-header .container { align-items: center; }
  .nav-hamburger { display: block; }
  .site-nav {
    display: none;
    position: absolute; top: 60px; left: 0; right: 0;
    flex-direction: column; align-items: stretch;
    background: var(--paper); border-bottom: 1px solid var(--line);
    padding: 8px 24px 16px;
  }
  .site-nav.open { display: flex; }
  .site-nav a { padding: 10px 4px; border-bottom: none; }
  .lang-toggle { margin: 8px 0 0; align-self: flex-start; }
}

/* ---------- Hero (front page) ---------- */
.hero {
  padding: 18px 0 14px;
  border-bottom: 1px solid var(--line);
}
.hero h1 {
  font-family: var(--serif);
  font-size: 1.25rem; font-weight: 700; letter-spacing: 0.03em;
}
.hero .hero-en { font-size: 0.9rem; color: var(--muted); margin-top: 2px; }
.hero .mission {
  max-width: 720px; margin-top: 4px;
  font-size: 0.88rem; color: var(--muted);
}

/* ---------- 2x2 matrix ---------- */
.matrix { padding: 24px 0; }
.matrix-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}
@media (max-width: 720px) { .matrix-grid { grid-template-columns: 1fr; } }

.quadrant {
  display: block; text-decoration: none; color: var(--text);
  background: var(--paper);
  padding: 18px 22px;
}
.quadrant:hover { background: var(--wash); }
.quad-head { display: flex; align-items: baseline; gap: 14px; }
.quad-char {
  font-family: var(--serif); font-size: 2.4rem; font-weight: 700;
  color: var(--accent); line-height: 1;
}
.quad-pinyin { font-size: 0.9rem; color: var(--muted); letter-spacing: 0.06em; }
.quad-title { margin-top: 6px; font-size: 1.05rem; font-weight: 600; }
.quad-desc { margin-top: 6px; color: var(--muted); font-size: 0.92rem; }
.quad-more { margin-top: 10px; font-size: 0.88rem; color: var(--accent); display: inline-block; }
.quad-img {
  display: block;
  max-width: 340px; width: 100%; height: auto;
  aspect-ratio: 2 / 1;
  object-fit: contain;
  margin: 10px auto 0;
  border: 1px solid var(--line);
}

/* ---------- Page sections ---------- */
.page-head {
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--line);
}
.page-head h1 { font-family: var(--serif); font-size: 1.9rem; }
.page-head .sub { color: var(--muted); margin-top: 4px; }

.section { padding: 40px 0; }
.section + .section { border-top: 1px solid var(--line); }
.section h2 {
  font-family: var(--serif); font-size: 1.3rem;
  margin-bottom: 18px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent);
  display: inline-block;
}
.section h2 .en-note { font-size: 0.85rem; color: var(--muted); font-weight: 400; margin-left: 10px; }
.section h3 { font-size: 1.05rem; margin: 18px 0 6px; }
.section p { margin: 8px 0; }

/* Cards & grids */
.card-grid {
  display: grid; gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}
.card {
  background: var(--paper); padding: 22px;
}
.card h3 { margin-top: 0; }
.card .role { color: var(--accent); font-size: 0.9rem; }

/* Publication list */
.pub-list { list-style: none; }
.pub-list li {
  padding: 14px 0; border-bottom: 1px solid var(--line);
  font-size: 0.96rem;
}
.pub-list .journal { font-style: italic; color: var(--accent); }
.pub-list .year { color: var(--muted); }

/* News list */
.news-item { padding: 16px 0; border-bottom: 1px solid var(--line); }
.news-item time { color: var(--muted); font-size: 0.85rem; }
.news-item h3 { margin: 4px 0; font-size: 1.05rem; }

/* Placeholder — visible marker for content the team must supply */
.placeholder {
  border: 1px dashed var(--accent);
  background: var(--wash);
  padding: 16px 18px;
  color: var(--muted);
  font-size: 0.92rem;
}
.placeholder::before {
  content: "✎ ";
  color: var(--accent);
}
html[lang="zh-CN"] .placeholder .ph-label::after { content: "（待补充）"; color: var(--accent); }
html[lang="en"] .placeholder .ph-label::after { content: " (to be added)"; color: var(--accent); }

/* Portrait / photo boxes */
.photo-box {
  aspect-ratio: 4 / 5; width: 100%;
  border: 1px dashed var(--line);
  background: var(--wash);
  display: flex; align-items: center; justify-content: center;
  color: var(--muted); font-size: 0.85rem; text-align: center; padding: 8px;
}
.pi-row {
  display: flex; gap: 36px; align-items: flex-start;
}
.pi-row .pi-bio { flex: 1; min-width: 0; }
@media (max-width: 640px) {
  .pi-row { flex-direction: column; }
}
.pi-photo {
  width: 240px; max-width: 100%;
  border: 1px solid var(--line);
  display: block;
  flex-shrink: 0;
}
img.responsive { max-width: 100%; }

/* Section illustrations (research page) */
.section-img {
  max-width: 380px; width: 100%;
  border: 1px solid var(--line);
  margin-top: 14px;
  display: block;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  background: var(--paper);
  padding: 14px 0; margin-top: 24px;
  font-size: 0.8rem; color: var(--muted);
}
.site-footer a { color: var(--muted); }
.site-footer p { margin: 2px 0; }

/* Utility */
.lead { font-size: 1.08rem; color: var(--muted); max-width: 760px; }
.inline-list { list-style: none; }
.inline-list li { padding: 6px 0; }
a { color: var(--accent); }