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

:root {
  --primary: #1e40af;
  --primary-light: #3b82f6;
  --dark: #0f172a;
  --text: #334155;
  --light-bg: #f1f5f9;
  --white: #ffffff;
  --border: #e2e8f0;
}

body {
  font-family: 'Segoe UI', system-ui, sans-serif;
  color: var(--text);
  line-height: 1.6;
}

/* NAV */
header {
  position: fixed;
  top: 0; left: 0; right: 0;
  background: rgba(15, 23, 42, 0.95);
  backdrop-filter: blur(8px);
  z-index: 100;
  padding: 0 2rem;
}

nav {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 60px;
}

.logo {
  color: var(--white);
  font-weight: 700;
  font-size: 1.2rem;
}

nav ul {
  list-style: none;
  display: flex;
  gap: 2rem;
}

nav ul a {
  color: #94a3b8;
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s;
}

nav ul a:hover { color: var(--white); }

/* HERO */
#hero {
  min-height: 100vh;
  background: linear-gradient(135deg, var(--dark) 0%, #1e3a5f 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 80px 2rem 2rem;
}

.hero-content h1 {
  font-size: 3.5rem;
  color: var(--white);
  margin-bottom: 0.5rem;
}

.hero-content .title {
  color: var(--primary-light);
  font-size: 1.2rem;
  margin-bottom: 1.5rem;
}

.hero-content .description {
  color: #94a3b8;
  font-size: 1.1rem;
  line-height: 1.8;
  margin-bottom: 2rem;
}

.hero-links { display: flex; gap: 1rem; justify-content: center; }

.btn {
  padding: 0.75rem 2rem;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 600;
  transition: all 0.2s;
  background: var(--primary);
  color: var(--white);
}

.btn:hover { background: var(--primary-light); transform: translateY(-2px); }

.btn-outline {
  background: transparent;
  border: 2px solid var(--primary-light);
  color: var(--primary-light);
}

.btn-outline:hover { background: var(--primary-light); color: var(--white); }

/* SECTIONS */
section { padding: 80px 2rem; }
.bg-light { background: var(--light-bg); }

.container {
  max-width: 1100px;
  margin: 0 auto;
}

h2 {
  font-size: 2rem;
  color: var(--dark);
  margin-bottom: 2.5rem;
  padding-bottom: 0.75rem;
  border-bottom: 3px solid var(--primary);
  display: inline-block;
}

/* ABOUT */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: start;
}

.about-text p { margin-bottom: 1.5rem; font-size: 1.05rem; }

.skills-list {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.skills-list li {
  background: var(--primary);
  color: var(--white);
  padding: 0.4rem 1rem;
  border-radius: 20px;
  font-size: 0.85rem;
}

.info-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem;
  margin-bottom: 1rem;
}

.info-card h3 {
  font-size: 0.85rem;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}

/* RESEARCH CARDS */
.card-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
}

.sub-tags {
  display: block;
  margin-top: 0.5rem;
  color: #60a5fa;
  font-size: 1rem;
  letter-spacing: 0.05em;
}

.card {
  background: var(--white);
  border-radius: 12px;
  padding: 2rem;
  border: 1px solid var(--border);
  transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

.card-icon { font-size: 2rem; margin-bottom: 1rem; }
.card h3 { color: var(--dark); margin-bottom: 0.75rem; }

/* PUBLICATIONS */
.publication-list { display: flex; flex-direction: column; gap: 1.5rem; }

.publication-item {
  display: flex;
  gap: 1.5rem;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  align-items: flex-start;
}

.year {
  font-weight: 700;
  color: var(--primary);
  font-size: 1.1rem;
  min-width: 50px;
}

.pub-content h3 { color: var(--dark); margin-bottom: 0.3rem; }
.journal { color: var(--primary-light); font-weight: 600; font-size: 0.9rem; }
.authors { color: #64748b; font-size: 0.9rem; }

/* CONTACT */
.contact-grid {
  display: flex;
  gap: 3rem;
  flex-wrap: wrap;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.contact-icon { font-size: 1.5rem; }
.contact-item a { color: var(--primary); text-decoration: none; }
.contact-item a:hover { text-decoration: underline; }

/* FOOTER */
footer {
  background: var(--dark);
  color: #64748b;
  text-align: center;
  padding: 1.5rem;
  font-size: 0.9rem;
}

/* RESPONSIVE */
@media (max-width: 768px) {
  .hero-content h1 { font-size: 2.5rem; }
  .about-grid { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: repeat(2, 1fr); }
  .contact-grid { flex-direction: column; gap: 1.5rem; }
}