/* ===== CSS Custom Properties ===== */
:root {
  --navy: #1a2744;
  --navy-light: #243564;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --accent-light: #eff6ff;
  --text-primary: #111827;
  --text-secondary: #4b5563;
  --text-muted: #9ca3af;
  --bg: #ffffff;
  --bg-alt: #f8fafc;
  --bg-alt2: #eef2ff;
  --border: #e5e7eb;
  --shadow-sm: 0 1px 3px rgba(0,0,0,.08), 0 1px 2px rgba(0,0,0,.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,.08), 0 2px 4px rgba(0,0,0,.04);
  --shadow-lg: 0 10px 30px rgba(0,0,0,.10);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.22s ease;
  --font: 'Inter', system-ui, -apple-system, sans-serif;
}

/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body { font-family: var(--font); color: var(--text-primary); background: var(--bg); line-height: 1.6; }
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
ul { list-style: none; }
button { cursor: pointer; border: none; background: none; font-family: inherit; }

/* ===== Inter font ===== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ===== Utility ===== */
.container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }
.section { padding: 80px 0; }
.section-alt { background: var(--bg-alt); }
.section-accent { background: var(--bg-alt2); }
.section-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--navy);
  text-align: center;
  margin-bottom: 12px;
}
.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  font-size: 1.05rem;
  margin-bottom: 52px;
  max-width: 560px;
  margin-left: auto;
  margin-right: auto;
}
.section-title-line {
  width: 52px;
  height: 4px;
  background: var(--accent);
  border-radius: 2px;
  margin: 12px auto 20px;
}

/* ===== Navbar ===== */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  transition: box-shadow var(--transition);
}
.navbar.scrolled { box-shadow: var(--shadow-md); }
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.nav-logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--navy);
  letter-spacing: -0.3px;
}
.nav-links {
  display: flex;
  gap: 6px;
}
.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 6px 14px;
  border-radius: 6px;
  transition: background var(--transition), color var(--transition);
}
.nav-links a:hover, .nav-links a.active {
  background: var(--accent-light);
  color: var(--accent);
}
.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 8px;
  border-radius: 6px;
  transition: background var(--transition);
}
.nav-hamburger:hover { background: var(--bg-alt); }
.nav-hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--navy);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}
.nav-hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-hamburger.open span:nth-child(2) { opacity: 0; }
.nav-hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ===== Hero ===== */
#hero {
  padding: 120px 0 80px;
  background: linear-gradient(135deg, #f8fafc 0%, #eff6ff 100%);
}
.hero-inner {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 60px;
  align-items: center;
}
.hero-photo-wrap {
  display: flex;
  justify-content: center;
}
.hero-photo {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  object-position: top;
  border: 4px solid #fff;
  box-shadow: var(--shadow-lg);
}
.hero-badge {
  display: inline-block;
  background: var(--accent-light);
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 600;
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 16px;
  letter-spacing: 0.3px;
}
.hero-name {
  font-size: 2.6rem;
  font-weight: 800;
  color: var(--navy);
  line-height: 1.15;
  margin-bottom: 10px;
  letter-spacing: -0.5px;
}
.hero-title {
  font-size: 1.2rem;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 8px;
}
.hero-location {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 6px;
}
.hero-tagline {
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 540px;
  margin-bottom: 28px;
  line-height: 1.7;
}
.hero-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  align-items: center;
  margin-bottom: 28px;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
  padding: 11px 26px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
  box-shadow: 0 2px 8px rgba(37,99,235,.25);
}
.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(37,99,235,.35);
}
.btn-secondary {
  border: 1.5px solid var(--border);
  color: var(--text-primary);
  padding: 10px 24px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  transition: border-color var(--transition), background var(--transition);
}
.btn-secondary:hover {
  border-color: var(--accent);
  background: var(--accent-light);
  color: var(--accent);
}
.hero-socials {
  display: flex;
  gap: 12px;
}
.social-link {
  display: flex;
  align-items: center;
  gap: 7px;
  color: var(--text-secondary);
  font-size: 0.88rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  border: 1px solid var(--border);
  transition: color var(--transition), border-color var(--transition), background var(--transition);
}
.social-link:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-light);
}
.social-link svg { width: 16px; height: 16px; flex-shrink: 0; }

/* ===== About ===== */
.about-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: start;
}
.about-text p {
  color: var(--text-secondary);
  font-size: 1.02rem;
  line-height: 1.75;
  margin-bottom: 16px;
}
.about-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.stat-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition);
}
.stat-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}
.stat-number {
  font-size: 2rem;
  font-weight: 800;
  color: var(--navy);
  display: block;
}
.stat-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* ===== Publications ===== */
.pub-grid {
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.pub-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow-sm);
  display: flex;
  gap: 20px;
  align-items: flex-start;
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
}
.pub-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: #bfdbfe;
}
.pub-id-badge {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  background: var(--navy);
  color: #fff;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.5px;
}
.pub-body { flex: 1; }
.pub-badges {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}
.badge {
  font-size: 0.76rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 20px;
  letter-spacing: 0.3px;
}
.badge-q1 { background: #fef3c7; color: #92400e; }
.badge-q2 { background: #f3f4f6; color: #374151; }
.badge-era { background: #ede9fe; color: #5b21b6; }
.badge-if { background: var(--accent-light); color: var(--accent); }
.badge-venue { background: #f0fdf4; color: #166534; }
.pub-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--navy);
  line-height: 1.4;
  margin-bottom: 6px;
}
.pub-authors {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}
.pub-venue {
  font-size: 0.88rem;
  color: var(--text-muted);
  font-style: italic;
  margin-bottom: 14px;
}
.pub-actions { display: flex; gap: 10px; }
.btn-pub {
  font-size: 0.85rem;
  font-weight: 600;
  padding: 7px 16px;
  border-radius: 6px;
  transition: background var(--transition), color var(--transition);
}
.btn-pub-primary {
  background: var(--accent);
  color: #fff;
}
.btn-pub-primary:hover { background: var(--accent-hover); }
.btn-pub-disabled {
  background: var(--bg-alt);
  color: var(--text-muted);
  cursor: not-allowed;
  font-size: 0.82rem;
}

/* ===== Experience ===== */
.timeline { position: relative; padding-left: 32px; }
.timeline::before {
  content: '';
  position: absolute;
  left: 10px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: var(--border);
  border-radius: 2px;
}
.timeline-item {
  position: relative;
  margin-bottom: 40px;
}
.timeline-item:last-child { margin-bottom: 0; }
.timeline-dot {
  position: absolute;
  left: -27px;
  top: 6px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid #fff;
  box-shadow: 0 0 0 3px #bfdbfe;
}
.timeline-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 28px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition);
}
.timeline-card:hover { box-shadow: var(--shadow-md); }
.timeline-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 16px;
  margin-bottom: 6px;
}
.timeline-company {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--navy);
}
.timeline-period {
  font-size: 0.83rem;
  color: var(--text-muted);
  white-space: nowrap;
  font-weight: 500;
  background: var(--bg-alt);
  padding: 3px 10px;
  border-radius: 20px;
}
.timeline-role {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 4px;
}
.timeline-location {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 14px;
}
.timeline-bullets {
  padding-left: 16px;
  list-style: disc;
}
.timeline-bullets li {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 5px;
}

/* ===== Skills ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}
.skill-category {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}
.skill-cat-title {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--accent);
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.skill-cat-title span {
  width: 20px;
  height: 2px;
  background: var(--accent);
  display: inline-block;
  border-radius: 2px;
}
.skill-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.skill-tag {
  background: var(--bg-alt);
  color: var(--text-primary);
  font-size: 0.83rem;
  font-weight: 500;
  padding: 5px 12px;
  border-radius: 6px;
  border: 1px solid var(--border);
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}
.skill-tag:hover {
  background: var(--accent-light);
  color: var(--accent);
  border-color: #bfdbfe;
}

/* ===== Education ===== */
.edu-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: 24px;
  max-width: 600px;
  margin: 0 auto;
}
.edu-icon {
  width: 56px;
  height: 56px;
  background: var(--navy);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  color: #fff;
  font-size: 1.5rem;
}
.edu-school {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 4px;
}
.edu-degree {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}
.edu-year {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* ===== Contact / Footer ===== */
#contact {
  background: var(--navy);
  color: #fff;
  padding: 64px 0 40px;
}
.contact-title {
  font-size: 2rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: 10px;
}
.contact-subtitle {
  text-align: center;
  color: #94a3b8;
  margin-bottom: 40px;
  font-size: 1rem;
}
.contact-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 14px;
  margin-bottom: 48px;
}
.contact-link {
  display: flex;
  align-items: center;
  gap: 8px;
  color: #e2e8f0;
  font-size: 0.92rem;
  font-weight: 500;
  padding: 10px 20px;
  border-radius: 8px;
  border: 1px solid rgba(255,255,255,.15);
  transition: background var(--transition), border-color var(--transition), color var(--transition);
}
.contact-link:hover {
  background: rgba(255,255,255,.1);
  border-color: rgba(255,255,255,.35);
  color: #fff;
}
.contact-link svg { width: 18px; height: 18px; }
.footer-divider {
  border: none;
  border-top: 1px solid rgba(255,255,255,.1);
  margin-bottom: 24px;
}
.footer-copy {
  text-align: center;
  color: #64748b;
  font-size: 0.85rem;
}

/* ===== Scroll-to-top ===== */
.scroll-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 44px;
  height: 44px;
  background: var(--accent);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition), transform var(--transition);
  z-index: 999;
}
.scroll-top.visible { opacity: 1; pointer-events: auto; }
.scroll-top:hover { transform: translateY(-2px); }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .nav-links { display: none; flex-direction: column; position: absolute; top: 64px; left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--border); padding: 12px 16px; gap: 4px; box-shadow: var(--shadow-md); }
  .nav-links.open { display: flex; }
  .nav-hamburger { display: flex; }

  .hero-inner { grid-template-columns: 1fr; text-align: center; gap: 28px; }
  .hero-photo-wrap { justify-content: center; }
  .hero-location { justify-content: center; }
  .hero-tagline { margin: 0 auto 28px; }
  .hero-actions { justify-content: center; }
  .hero-socials { justify-content: center; flex-wrap: wrap; }

  .about-inner { grid-template-columns: 1fr; gap: 36px; }
  .timeline { padding-left: 24px; }
  .timeline-header { flex-direction: column; gap: 6px; }

  .section-title { font-size: 1.6rem; }
  .hero-name { font-size: 2rem; }

  .contact-links { flex-direction: column; align-items: center; }
  .edu-card { flex-direction: column; text-align: center; }
}

@media (max-width: 480px) {
  .hero-name { font-size: 1.7rem; }
  .pub-card { flex-direction: column; gap: 14px; }
  .about-stats { grid-template-columns: 1fr 1fr; }
}