:root {
  --color-bg: #f8f9fa;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #6b7280;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-accent-light: #eff4ff;
  --color-border: #e5e7eb;
  --color-nav-bg: rgba(255, 255, 255, 0.85);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.05);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --max-width: 860px;
  --radius: 12px;
  --transition: 0.2s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-accent-hover);
}

/* ── Navigation ── */

nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-nav-bg);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--color-border);
  padding: 0 24px;
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-name {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.nav-name:hover {
  color: var(--color-accent);
}

.nav-links {
  display: flex;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: color var(--transition);
  position: relative;
  padding-bottom: 4px;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-accent);
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--color-accent);
  border-radius: 1px;
}

/* ── Main ── */

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 48px 24px 80px;
}

/* ── Hero (index page) ── */

.hero {
  display: flex;
  align-items: flex-start;
  gap: 48px;
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 48px;
  box-shadow: var(--shadow-md);
  animation: fadeInUp 0.5s ease both;
}

.hero-image {
  flex-shrink: 0;
}

.hero-image img {
  width: 220px;
  height: 220px;
  object-fit: cover;
  border-radius: 50%;
  box-shadow: var(--shadow-lg);
  border: 4px solid var(--color-accent-light);
}

.hero-text h1 {
  font-size: 2.1rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 6px;
  line-height: 1.2;
}

.hero-text .tagline {
  font-size: 1.05rem;
  color: var(--color-accent);
  font-weight: 600;
  margin-bottom: 20px;
}

.hero-text p {
  color: var(--color-text-secondary);
  font-size: 1rem;
  margin-bottom: 12px;
  line-height: 1.75;
}

.hero-text a {
  font-weight: 500;
}

.hero-text a:hover {
  text-decoration: underline;
}

/* ── Section headings ── */

.section {
  margin-top: 48px;
  animation: fadeInUp 0.5s ease both;
  animation-delay: 0.1s;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.section-header h2 {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  position: relative;
}

.section-header h2::after {
  content: '';
  display: block;
  width: 40px;
  height: 3px;
  background: var(--color-accent);
  border-radius: 2px;
  margin-top: 6px;
}

.section h3 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 16px;
  margin-top: 32px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  font-size: 0.85rem;
}

/* ── Research interests card ── */

.interests-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 28px 32px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
}

.interests-card > p {
  color: var(--color-text-secondary);
  margin-bottom: 16px;
  line-height: 1.75;
}

.interests-list {
  list-style: none;
  padding: 0;
}

.interests-list li {
  position: relative;
  padding-left: 22px;
  margin-bottom: 12px;
  color: var(--color-text-secondary);
  line-height: 1.65;
}

.interests-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 9px;
  width: 8px;
  height: 8px;
  background: var(--color-accent);
  border-radius: 50%;
}

.interests-list li strong {
  color: var(--color-text);
  font-weight: 600;
}

/* ── Publication cards ── */

.pub-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.pub-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 24px 28px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  transition: box-shadow var(--transition), transform var(--transition);
}

.pub-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.pub-title {
  font-weight: 600;
  font-size: 1.05rem;
  margin-bottom: 6px;
  line-height: 1.4;
}

.pub-title a:hover {
  text-decoration: underline;
}

.pub-authors {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.pub-authors .me {
  color: var(--color-text);
  font-weight: 600;
}

.pub-venue {
  font-style: italic;
  font-size: 0.9rem;
  color: var(--color-accent);
  font-weight: 500;
}

/* ── Working project cards ── */

.project-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.project-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 24px 28px;
  box-shadow: var(--shadow-sm);
  border-left: 4px solid var(--color-accent);
  transition: box-shadow var(--transition);
}

.project-card:hover {
  box-shadow: var(--shadow-md);
}

.project-card h4 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.project-card p {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.65;
}

/* ── Contact card ── */

.contact-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 40px;
  box-shadow: var(--shadow-md);
  max-width: 520px;
  animation: fadeInUp 0.5s ease both;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 16px;
  padding: 18px 20px;
  background: var(--color-bg);
  border-radius: 10px;
  transition: transform var(--transition);
}

.contact-item:last-child {
  margin-bottom: 0;
}

.contact-item:hover {
  transform: translateX(4px);
}

.contact-icon {
  font-size: 1.25rem;
  color: var(--color-accent);
  width: 28px;
  text-align: center;
  flex-shrink: 0;
}

.contact-details .contact-label {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-secondary);
  margin-bottom: 2px;
  font-weight: 500;
}

.contact-details .contact-value {
  font-weight: 500;
  color: var(--color-text);
  font-size: 0.95rem;
}

/* ── Footer ── */

footer {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 24px;
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  border-top: 1px solid var(--color-border);
}

footer a {
  color: var(--color-text-secondary);
  font-weight: 500;
}

footer a:hover {
  color: var(--color-accent);
}

/* ── Animations ── */

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ── Responsive ── */

@media (max-width: 768px) {
  .hero {
    flex-direction: column;
    align-items: center;
    text-align: center;
    padding: 36px 28px;
    gap: 28px;
  }

  .hero-image img {
    width: 160px;
    height: 160px;
  }

  .hero-text h1 {
    font-size: 1.75rem;
  }

  .nav-links {
    gap: 20px;
  }

  main {
    padding: 32px 16px 64px;
  }

  .contact-card {
    padding: 28px 24px;
  }
}

@media (max-width: 480px) {
  .nav-inner {
    flex-direction: column;
    height: auto;
    padding: 12px 0;
    gap: 8px;
  }

  .nav-links {
    gap: 16px;
  }

  .hero {
    padding: 28px 20px;
  }

  .pub-card {
    padding: 20px;
  }
}