/* ===== CSS Variables & Reset ===== */
:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f7f7f8;
  --color-surface: #ffffff;
  --color-text: #111111;
  --color-text-secondary: #3a3a3a;
  --color-text-muted: #6b6b6b;
  --color-accent: #1a3a5c;
  --color-accent-hover: #0f2a45;
  --color-accent-light: #eef2f7;
  --color-accent-warm: #8b2332;
  --color-border: #d4d4d4;
  --color-border-light: #e8e8e8;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-serif: 'Source Serif 4', 'Georgia', 'Times New Roman', serif;
  --max-width: 880px;
  --nav-height: 56px;
  --transition: 0.2s ease;
}

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

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

body {
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.65;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

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

/* ===== Navigation ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid transparent;
  z-index: 100;
  transition: border-color var(--transition);
}

.nav.scrolled {
  border-bottom-color: var(--color-border);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 28px;
}

.nav-links a {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  transition: color var(--transition);
}

.nav-links a:hover {
  color: var(--color-text);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  flex-direction: column;
  gap: 5px;
}

.nav-toggle span {
  display: block;
  width: 20px;
  height: 1.5px;
  background: var(--color-text);
  transition: var(--transition);
}

/* ===== Hero ===== */
.hero {
  padding: 140px 0 80px;
  min-height: 80vh;
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--color-border-light);
}

.hero-layout {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 48px;
}

.hero-content {
  max-width: 520px;
  flex: 1;
}

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

.hero-photo img {
  width: 220px;
  height: 220px;
  object-fit: cover;
  border-radius: 4px;
  border: 2px solid var(--color-border);
  filter: grayscale(15%);
}

.hero-greeting {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-accent);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 12px;
}

.hero-name {
  font-family: var(--font-serif);
  font-size: clamp(2.6rem, 5.5vw, 3.6rem);
  font-weight: 700;
  line-height: 1.1;
  color: var(--color-text);
  margin-bottom: 14px;
  letter-spacing: -0.02em;
}

.hero-tagline {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  font-weight: 400;
  font-style: italic;
  color: var(--color-text-secondary);
  margin-bottom: 14px;
}

.hero-sub {
  font-size: 0.925rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: 28px;
}

.hero-links {
  display: flex;
  gap: 12px;
  margin-bottom: 36px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  padding: 10px 24px;
  font-size: 0.825rem;
  font-weight: 600;
  border-radius: 4px;
  text-decoration: none;
  transition: all var(--transition);
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-accent-hover);
}

.btn-outline {
  background: transparent;
  color: var(--color-accent);
  border: 1.5px solid var(--color-accent);
}

.btn-outline:hover {
  background: var(--color-accent);
  color: #fff;
}

.hero-social {
  display: flex;
  gap: 18px;
}

.hero-social a {
  color: var(--color-text-muted);
  transition: color var(--transition);
}

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

/* ===== Sections ===== */
.section {
  padding: 80px 0;
}

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

.section-title {
  font-family: var(--font-serif);
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 40px;
  color: var(--color-text);
  letter-spacing: -0.01em;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--color-text);
  display: inline-block;
}

.section-title::after {
  display: none;
}

/* ===== About ===== */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 48px;
  align-items: start;
}

.about-text p {
  margin-bottom: 14px;
  color: var(--color-text-secondary);
  font-size: 0.925rem;
}

.about-text p:last-child {
  margin-bottom: 0;
}

.about-text strong {
  color: var(--color-text);
  font-weight: 600;
}

.about-highlights {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.highlight-card {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border-light);
  border-radius: 4px;
  padding: 20px 16px;
  text-align: center;
}

.highlight-number {
  display: block;
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-accent);
  margin-bottom: 2px;
}

.highlight-label {
  font-size: 0.72rem;
  color: var(--color-text-muted);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ===== Timeline ===== */
.timeline {
  position: relative;
  padding-left: 28px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 5px;
  top: 6px;
  bottom: 6px;
  width: 1.5px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  margin-bottom: 32px;
}

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

.timeline-marker {
  position: absolute;
  left: -28px;
  top: 8px;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  background: var(--color-accent);
  z-index: 1;
}

.timeline-content {
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-left: 3px solid var(--color-accent);
  border-radius: 2px;
  padding: 24px 28px;
}

.section-alt .timeline-content {
  background: #fff;
}

.timeline-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 14px;
  gap: 16px;
}

.timeline-header h3 {
  font-family: var(--font-serif);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text);
  line-height: 1.3;
}

.timeline-institution {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-top: 2px;
  font-style: italic;
}

.timeline-date {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--color-accent);
  white-space: nowrap;
  flex-shrink: 0;
  letter-spacing: 0.02em;
}

.timeline-content ul {
  list-style: none;
  padding: 0;
}

.timeline-content li {
  position: relative;
  padding-left: 16px;
  margin-bottom: 8px;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.timeline-content li:last-child {
  margin-bottom: 0;
}

.timeline-content li::before {
  content: '\2013';
  position: absolute;
  left: 0;
  top: 0;
  color: var(--color-text-muted);
  font-weight: 400;
}

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

/* ===== Publications ===== */
.publications {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.pub-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-left: 4px solid var(--color-accent);
  border-radius: 2px;
  padding: 24px 28px;
}

.pub-card-wip {
  border-left-color: var(--color-text-muted);
}

.pub-card-service {
  border-left-color: var(--color-accent-warm);
}

.pub-venue {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-accent);
  background: var(--color-accent-light);
  padding: 3px 8px;
  border-radius: 2px;
  margin-bottom: 10px;
}

.pub-card-wip .pub-venue {
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
}

.pub-card-service .pub-venue {
  color: var(--color-accent-warm);
  background: #fdf2f3;
}

.pub-title {
  font-family: var(--font-serif);
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 6px;
  line-height: 1.4;
}

.pub-authors {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 8px;
}

.pub-desc {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ===== Skills ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
}

.skill-category {
  border: 1px solid var(--color-border-light);
  border-radius: 2px;
  padding: 20px;
  background: var(--color-surface);
}

.skill-category h3 {
  font-family: var(--font-serif);
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 14px;
  color: var(--color-text);
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border-light);
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.skill-tags span {
  font-size: 0.78rem;
  font-weight: 500;
  padding: 4px 10px;
  background: var(--color-bg-alt);
  color: var(--color-text-secondary);
  border-radius: 2px;
  border: 1px solid var(--color-border-light);
}

/* ===== Contact ===== */
.contact-text {
  font-size: 1rem;
  color: var(--color-text-secondary);
  max-width: 580px;
  margin-bottom: 32px;
}

.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 12px;
}

.contact-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 20px;
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: 2px;
  text-decoration: none;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  transition: border-color var(--transition), color var(--transition);
}

.contact-card:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.contact-card svg {
  flex-shrink: 0;
  opacity: 0.6;
}

.contact-card:hover svg {
  opacity: 1;
}

/* ===== Footer ===== */
.footer {
  padding: 28px 0;
  text-align: center;
  border-top: 1px solid var(--color-border);
}

.footer p {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

/* ===== Animations ===== */
.fade-in {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

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

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: 12px 24px;
    gap: 0;
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links li a {
    display: block;
    padding: 10px 0;
    font-size: 0.85rem;
  }

  .nav-toggle {
    display: flex;
  }

  .hero {
    padding: 110px 0 56px;
    min-height: auto;
  }

  .hero-layout {
    flex-direction: column-reverse;
    gap: 32px;
    align-items: flex-start;
  }

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

  .hero-name {
    font-size: 2.2rem;
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .about-highlights {
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
  }

  .highlight-card {
    padding: 14px 10px;
  }

  .highlight-number {
    font-size: 1.2rem;
  }

  .timeline {
    padding-left: 20px;
  }

  .timeline-marker {
    left: -20px;
    width: 9px;
    height: 9px;
  }

  .timeline-content {
    padding: 18px;
  }

  .timeline-header {
    flex-direction: column;
    gap: 6px;
  }

  .pub-card {
    padding: 18px;
  }

  .skills-grid {
    grid-template-columns: 1fr;
  }

  .section {
    padding: 56px 0;
  }
}

@media (max-width: 480px) {
  .about-highlights {
    grid-template-columns: 1fr 1fr;
  }

  .hero-links {
    flex-direction: column;
  }

  .btn {
    text-align: center;
    justify-content: center;
  }
}