/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ── CSS custom properties ── */
:root {
  --bg-card:    rgba(255, 255, 255, 0.91);
  --bg-header:  rgba(255, 255, 255, 0.96);
  --text:       #111;
  --text-muted: #555;
  --text-faint: #999;
  --border:     #e8e8e8;
  --link-ul:    #ccc;
}
[data-theme="dark"] {
  --bg-card:    rgba(12, 12, 18, 0.91);
  --bg-header:  rgba(8, 8, 14, 0.97);
  --text:       #ececec;
  --text-muted: #aaaaaa;
  --text-faint: #666;
  --border:     #2a2a36;
  --link-ul:    #3a3a50;
}

/* ── Body / background ── */
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
  color: var(--text);
  font-size: 16px;
  line-height: 1.6;
  background-image: url('Background_hres.png');
  background-size: cover;
  background-attachment: fixed;
  background-position: center center;
  background-repeat: no-repeat;
  background-color: #07070f;
  min-height: 100vh;
  transition: color 0.2s;
}
a { color: inherit; text-decoration: none; }

/* ── Navigation ── */
.site-header {
  position: sticky; top: 0;
  background: var(--bg-header);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  z-index: 100;
  transition: background 0.2s, border-color 0.2s;
}
.nav-inner {
  max-width: 900px; margin: 0 auto;
  padding: 0 1.5rem; height: 60px;
  display: flex; align-items: center; justify-content: space-between;
}
.nav-logo a { font-size: 1rem; font-weight: 500; color: var(--text); transition: color 0.2s; }
.nav-links { display: flex; gap: 2rem; list-style: none; }
.nav-links a { font-size: 0.88rem; color: var(--text-faint); transition: color 0.15s; }
.nav-links a:hover, .nav-links a.active { color: var(--text); }

/* ── Nav controls (theme toggle + mobile menu) ── */
.nav-controls { display: flex; align-items: center; gap: 0.6rem; }
.theme-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 7px;
  width: 34px; height: 34px;
  font-size: 1rem;
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  transition: border-color 0.15s;
  flex-shrink: 0;
}
.theme-btn:hover { border-color: var(--text-muted); }

.menu-btn {
  display: none; background: none; border: none;
  font-size: 0.88rem; color: var(--text-faint); cursor: pointer; font-family: inherit;
}
.mobile-nav {
  display: none; flex-direction: column;
  padding: 1rem 1.5rem 1.25rem;
  border-top: 1px solid var(--border);
  gap: 1rem;
  background: var(--bg-header);
}
.mobile-nav.open { display: flex; }
.mobile-nav a { font-size: 0.88rem; color: var(--text-faint); }

/* ── Main content card ── */
main {
  max-width: 900px;
  margin: 2rem auto;
  padding: 2.75rem 2rem 5rem;
  background: var(--bg-card);
  border-radius: 14px;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border: 1px solid var(--border);
  transition: background 0.2s, border-color 0.2s;
}

/* ── Social / icon links ── */
.social-links {
  display: flex; gap: 0.65rem; flex-wrap: wrap; margin-top: 1.75rem;
}
.social-link {
  display: inline-flex; align-items: center; gap: 0.45rem;
  font-size: 0.81rem; color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.38rem 0.85rem;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}
.social-link:hover {
  color: var(--text);
  border-color: var(--text-muted);
  background: rgba(128,128,128,0.06);
}
.social-link i { font-size: 0.92rem; }

/* ── Home - hero ── */
.hero { margin-bottom: 4.5rem; }
.hero h1 {
  font-size: 2.4rem; font-weight: 500;
  letter-spacing: -0.03em; margin-bottom: 0.45rem;
  color: var(--text);
}
.hero .role   { font-size: 1rem; color: var(--text-muted); margin-bottom: 0.15rem; }
.hero .institute { font-size: 0.9rem; color: var(--text-faint); }

.hero-links { display: flex; gap: 1.25rem; flex-wrap: wrap; margin-top: 1.4rem; }
.hero-links a {
  font-size: 0.83rem; color: var(--text-muted);
  border-bottom: 1px solid var(--link-ul);
  padding-bottom: 1px;
  transition: color 0.15s, border-color 0.15s;
}
.hero-links a:hover { color: var(--text); border-color: var(--text); }

/* ── Home - institute link ── */
.institute-link {
  color: var(--text-faint);
  border-bottom: 1px solid var(--link-ul);
  transition: color 0.15s, border-color 0.15s;
}
.institute-link:hover { color: var(--text); border-color: var(--text); }

/* ── Home - blurb ── */
.home-blurb {
  margin-bottom: 4rem;
  padding-top: 0.25rem;
}
.home-blurb p {
  font-size: 0.9rem; color: var(--text-muted);
  line-height: 1.9; max-width: 680px; margin-bottom: 1rem;
}
.inline-link {
  border-bottom: 1px solid var(--link-ul);
  color: var(--text-muted);
  transition: color 0.15s, border-color 0.15s;
}
.inline-link:hover { color: var(--text); border-color: var(--text); }

/* ── Home - contact ── */
.contact-section h2 { font-size: 1.05rem; font-weight: 500; margin-bottom: 1.1rem; color: var(--text); }
.contact-section address {
  font-style: normal; font-size: 0.88rem;
  color: var(--text-muted); line-height: 2.1;
}
.contact-section address strong {
  display: block; color: var(--text); font-weight: 500; margin-bottom: 0.05rem;
}
.contact-section address a {
  border-bottom: 1px solid var(--link-ul);
  transition: border-color 0.15s, color 0.15s;
}
.contact-section address a:hover { color: var(--text); border-color: var(--text); }

/* ── Generic page heading ── */
.page-title {
  font-size: 2rem; font-weight: 500;
  letter-spacing: -0.03em; margin-bottom: 2rem;
  color: var(--text);
}

/* ── About - intro photo + text ── */
.about-intro {
  display: flex;
  align-items: flex-start;
  gap: 2.25rem;
  margin-bottom: 2rem;
}
.about-photo {
  width: 300px;
  flex-shrink: 0;
  border-radius: 12px;
  object-fit: cover;
  filter: drop-shadow(0 4px 18px rgba(0,0,0,0.12));
}
.about-intro-text { flex: 1; }
.about-intro-text p {
  font-size: 0.9rem; color: var(--text-muted);
  line-height: 1.9; max-width: 680px; margin-bottom: 1rem;
}

@media (max-width: 620px) {
  .about-intro { flex-direction: column; align-items: center; }
  .about-photo { width: 150px; }
}

/* ── About ── */
.page-body p {
  font-size: 0.9rem; color: var(--text-muted);
  line-height: 1.9; max-width: 680px; margin-bottom: 1.3rem;
}
.page-body h2 {
  font-size: 1.05rem; font-weight: 500;
  color: var(--text); margin-top: 2.25rem; margin-bottom: 0.75rem;
}
.bullet-list { list-style: disc; padding-left: 1.4rem; margin-bottom: 1.25rem; }
.bullet-list li { font-size: 0.9rem; color: var(--text-muted); margin-bottom: 0.35rem; line-height: 1.7; }

/* ── Research ── */
.research-subtitle {
  font-size: 0.9rem; color: var(--text-faint);
  margin-top: -1.5rem; margin-bottom: 2.5rem;
}
.project-block { margin-bottom: 2.5rem; }
.project-block h2 { font-size: 1.05rem; font-weight: 500; color: var(--text); margin-bottom: 0.55rem; }
.project-block p  { font-size: 0.9rem; color: var(--text-muted); line-height: 1.9; max-width: 680px; margin-bottom: 0.75rem; }
.project-block ul { list-style: disc; padding-left: 1.4rem; }
.project-block ul li { font-size: 0.88rem; color: var(--text-muted); margin-bottom: 0.3rem; }
.divider { border: none; border-top: 1px solid var(--border); margin: 2.5rem 0; }

/* ── Papers ── */
.papers-section-heading {
  font-size: 1.05rem; font-weight: 500;
  color: var(--text); margin-bottom: 0.25rem; margin-top: 2.5rem;
}
.papers-section-heading:first-child { margin-top: 0; }
.papers-list { list-style: none; margin-top: 0.5rem; }
.paper { padding: 1.4rem 0; border-top: 1px solid var(--border); }
.paper:last-child { border-bottom: 1px solid var(--border); }
.paper-title { font-size: 0.9rem; font-weight: 500; margin-bottom: 0.3rem; color: var(--text); }
.paper-authors { font-size: 0.83rem; color: var(--text-muted); margin-bottom: 0.2rem; }
.paper-authors b { color: var(--text); }
.paper-venue { font-size: 0.8rem; color: var(--text-faint); font-style: italic; margin-bottom: 0.55rem; }
.paper-links { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.paper-link {
  font-size: 0.8rem; color: var(--text-muted);
  border-bottom: 1px solid var(--link-ul);
  padding-bottom: 1px;
  transition: color 0.15s, border-color 0.15s;
}
.paper-link:hover { color: var(--text); border-color: var(--text); }

/* ── Mobile ── */
@media (max-width: 620px) {
  .nav-links { display: none; }
  .menu-btn  { display: block; }
  .hero h1   { font-size: 1.8rem; }
  main       { margin: 1rem; padding: 1.75rem 1.25rem 3.5rem; border-radius: 10px; }
}