/* ===== CSS Custom Properties ===== */
:root {
  --color-primary: #1a1a2e;
  --color-text: #333;
  --color-text-light: #6c757d;
  --color-accent: #dc3545;
  --color-accent-dark: #b02a37;
  --color-bg: #ffffff;
  --color-bg-alt: #f8f9fa;
  --color-border: #e9ecef;
  --color-link: #2563eb;
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --max-width: 960px;
  --nav-height: 60px;
  --radius: 8px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.1);
  --transition: 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 24px);
}

body {
  font-family: var(--font-main);
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

img {
  max-width: 100%;
  height: auto;
  display: block;
}

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

/* ===== Navigation ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
  transition: box-shadow var(--transition);
}

.navbar.scrolled {
  box-shadow: var(--shadow-sm);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: -0.02em;
}

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

.nav-links {
  display: flex;
  align-items: center;
  list-style: none;
  gap: 8px;
}

.nav-links a {
  display: block;
  padding: 6px 14px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-light);
  border-radius: 6px;
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-primary);
  background: var(--color-bg-alt);
}

.nav-contact {
  background: var(--color-primary) !important;
  color: #fff !important;
}

.nav-contact:hover {
  background: var(--color-accent) !important;
  color: #fff !important;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-primary);
  border-radius: 2px;
  transition: all var(--transition);
}

/* ===== Hero Section ===== */
.hero {
  padding-top: calc(var(--nav-height) + 60px);
  padding-bottom: 60px;
  background: var(--color-bg);
}

.hero-container {
  display: flex;
  align-items: center;
  gap: 60px;
}

.hero-photo img {
  width: 220px;
  height: 220px;
  border-radius: 50%;
  object-fit: cover;
  box-shadow: var(--shadow-lg);
  border: 4px solid #fff;
}

.hero-text h1 {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: -0.03em;
  line-height: 1.2;
}

.hero-title {
  font-size: 1.2rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-top: 4px;
}

.hero-affiliation {
  font-size: 1.05rem;
  color: var(--color-text-light);
  margin-top: 2px;
}

.hero-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 20px;
}

.hero-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text);
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 100px;
  transition: all var(--transition);
}

.hero-link:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background: #fff;
  box-shadow: var(--shadow-sm);
  transform: translateY(-1px);
}

.hero-link svg {
  flex-shrink: 0;
}

/* ===== Sections ===== */
.section {
  padding: 72px 0;
}

.section-alt {
  background: var(--color-bg-alt);
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: -0.02em;
  margin-bottom: 32px;
  padding-bottom: 12px;
  border-bottom: 3px solid var(--color-accent);
  display: inline-block;
}

/* ===== About Section ===== */
.about-content p {
  font-size: 1.05rem;
  line-height: 1.8;
  margin-bottom: 16px;
  max-width: 720px;
}

.about-content a {
  font-weight: 500;
}

.research-interests {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 20px;
}

.tag {
  display: inline-block;
  padding: 6px 16px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-accent-dark);
  background: #fce4e6;
  border-radius: 100px;
  letter-spacing: 0.01em;
}

/* ===== News Section ===== */
.news-list {
  list-style: none;
  max-width: 720px;
}

.news-list li {
  display: flex;
  gap: 20px;
  padding: 14px 0;
  border-bottom: 1px solid var(--color-border);
  align-items: baseline;
}

.news-list li:last-child {
  border-bottom: none;
}

.news-date {
  flex-shrink: 0;
  width: 90px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-accent);
}

.news-text {
  font-size: 0.95rem;
  color: var(--color-text);
}

/* ===== Publications Section ===== */
.pub-category {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-light);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-top: 36px;
  margin-bottom: 20px;
}

.pub-category:first-of-type {
  margin-top: 0;
}

.pub-list {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.pub-item {
  padding: 20px 24px;
  background: var(--color-bg-alt);
  border-radius: var(--radius);
  border-left: 3px solid var(--color-border);
  transition: all var(--transition);
}

.pub-item:hover {
  border-left-color: var(--color-accent);
  box-shadow: var(--shadow-sm);
  transform: translateX(4px);
}

.pub-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-primary);
  line-height: 1.5;
  margin-bottom: 6px;
}

.pub-authors {
  font-size: 0.875rem;
  color: var(--color-text-light);
  margin-bottom: 8px;
  line-height: 1.5;
}

.pub-venue {
  display: inline-block;
  padding: 3px 12px;
  font-size: 0.75rem;
  font-weight: 700;
  color: #fff;
  background: var(--color-primary);
  border-radius: 4px;
  letter-spacing: 0.03em;
}

.venue-review {
  background: var(--color-text-light);
}

.venue-preprint {
  background: #6c757d;
}

.pub-links {
  display: inline-flex;
  gap: 8px;
  margin-left: 8px;
  vertical-align: middle;
}

.pub-pdf {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-accent);
  border: 1px solid var(--color-accent);
  border-radius: 4px;
  transition: all var(--transition);
  text-decoration: none;
}

.pub-pdf:hover {
  color: #fff;
  background: var(--color-accent);
}

/* ===== Experience Section ===== */
.experience-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

.exp-heading {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 24px;
}

.exp-item {
  padding: 20px 0;
  border-bottom: 1px solid var(--color-border);
}

.exp-item:last-child {
  border-bottom: none;
}

.exp-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
}

.exp-header h4 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-primary);
}

.exp-location {
  font-size: 0.85rem;
  color: var(--color-text-light);
  font-weight: 500;
}

.exp-role {
  font-size: 0.9rem;
  color: var(--color-text);
  margin-top: 2px;
}

.exp-date {
  font-size: 0.8rem;
  color: var(--color-text-light);
  font-weight: 500;
  margin-top: 2px;
}

.exp-details {
  margin-top: 8px;
  padding-left: 18px;
  font-size: 0.85rem;
  color: var(--color-text-light);
  line-height: 1.7;
}

.exp-details li {
  margin-bottom: 4px;
}

/* ===== Service Section ===== */
.service-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
}

.service-item {
  padding: 24px;
  background: var(--color-bg-alt);
  border-radius: var(--radius);
}

.service-item h4 {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 8px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.service-item p {
  font-size: 0.875rem;
  color: var(--color-text-light);
  line-height: 1.6;
  margin-bottom: 4px;
}

/* ===== Footer ===== */
.footer {
  background: var(--color-primary);
  color: rgba(255, 255, 255, 0.7);
  padding: 48px 0 32px;
}

.footer-container {
  text-align: center;
}

.footer-name {
  font-size: 1.2rem;
  font-weight: 700;
  color: #fff;
  margin-bottom: 4px;
}

.footer-info p {
  font-size: 0.9rem;
  margin-bottom: 4px;
}

.footer-contact {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-top: 20px;
  margin-bottom: 24px;
}

.footer-contact a {
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.875rem;
  font-weight: 500;
  transition: color var(--transition);
}

.footer-contact a:hover {
  color: #fff;
}

.footer-copy {
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.4);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding-top: 20px;
}

/* ===== Animations ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  :root {
    --nav-height: 56px;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-links {
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    padding: 16px 24px;
    gap: 4px;
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: all 0.3s ease;
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .nav-links a {
    padding: 10px 16px;
    font-size: 0.95rem;
  }

  .hero {
    padding-top: calc(var(--nav-height) + 40px);
    padding-bottom: 40px;
  }

  .hero-container {
    flex-direction: column;
    text-align: center;
    gap: 32px;
  }

  .hero-photo img {
    width: 180px;
    height: 180px;
  }

  .hero-text h1 {
    font-size: 2rem;
  }

  .hero-links {
    justify-content: center;
  }

  .section {
    padding: 48px 0;
  }

  .section-title {
    font-size: 1.5rem;
  }

  .experience-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .service-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .news-list li {
    flex-direction: column;
    gap: 4px;
  }

  .news-date {
    width: auto;
  }

  .pub-item {
    padding: 16px;
  }
}

@media (max-width: 480px) {
  .hero-text h1 {
    font-size: 1.75rem;
  }

  .hero-link span {
    display: none;
  }

  .hero-link {
    padding: 10px;
  }

  .container {
    padding: 0 16px;
  }
}