/* ============================================
   Design System — Custom Properties
   ============================================ */
:root {
  /* Colors */
  --bg-primary: #fff;
  --bg-secondary: #f8f9fa;
  --accent: #4a7c96;
  --accent-hover: #5a9ab5;
  --text-primary: #333;
  --text-secondary: #555;
  --text-muted: #888;
  --border-subtle: #ebebeb;
  --border-card: #e0e0e0;

  /* Typography */
  --font-sans: 'Noto Sans', 'Inter', system-ui, -apple-system, sans-serif;
  --font-heading: 'Roboto Slab', Georgia, serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  /* Layout */
  --content-max-width: 50rem;
  --radius-sm: 0.5rem;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
}

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

html {
  scroll-behavior: smooth;
  font-size: 15px;
}

@media screen and (min-width: 42em) {
  html { font-size: 16px; }
}

body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: 1.75;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

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

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

strong {
  font-weight: 700;
}

/* ============================================
   Layout — Single Column
   ============================================ */
.page {
  max-width: var(--content-max-width);
  margin: 0 auto;
  padding: var(--space-3xl) var(--space-md) var(--space-xl);
}

/* ============================================
   Intro (name, bio, links, photo)
   ============================================ */
.intro {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
  margin-bottom: var(--space-2xl);
}

.intro-text {
  flex: 1;
  min-width: 0;
}

.name {
  font-family: var(--font-heading);
  font-size: var(--font-size-3xl);
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: var(--space-md);
}

.intro-text p {
  color: var(--text-secondary);
  margin-bottom: var(--space-md);
}

.intro .links {
  margin-bottom: 0;
}

.sep {
  color: var(--text-muted);
  margin: 0 var(--space-xs);
}

.intro-photo {
  flex: 0 0 13rem;
}

.intro-photo img {
  width: 13rem;
  height: 13rem;
  object-fit: cover;
  border-radius: 50%;
}

/* ============================================
   Sections
   ============================================ */
.section {
  margin-bottom: var(--space-2xl);
}

.section-title {
  font-family: var(--font-heading);
  font-size: var(--font-size-2xl);
  font-weight: 700;
  margin-bottom: var(--space-lg);
  position: relative;
  padding-bottom: var(--space-sm);
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 2.5rem;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
}

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

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

/* News, Service, Teaching */
.news-list,
.plain-list {
  list-style: none;
}

.news-list li,
.plain-list li {
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
}

.news-list li {
  display: flex;
  gap: var(--space-md);
}

.news-date {
  flex: 0 0 5.5rem;
  font-weight: 600;
  color: var(--text-primary);
}

/* ============================================
   Research Interests
   ============================================ */
.interest-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-lg);
}

.interest-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  padding: var(--space-lg);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
}

.interest-card:hover {
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
  transform: translateY(-2px);
}

.interest-card-icon {
  font-size: var(--font-size-2xl);
  display: block;
  margin-bottom: var(--space-sm);
}

.interest-card h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.interest-card p {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ============================================
   Publications
   ============================================ */
.pub {
  display: flex;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
}

.pub-media {
  flex: 0 0 15rem;
}

.pub-media video,
.pub-media img {
  width: 100%;
  border-radius: var(--radius-sm);
  display: block;
}

.pub-info {
  flex: 1;
  min-width: 0;
  font-size: var(--font-size-sm);
  line-height: 1.6;
}

.pub-info p {
  margin-top: var(--space-xs);
}

.pub-title {
  font-size: var(--font-size-base);
  font-weight: 600;
}

.pub-authors {
  color: var(--text-secondary);
}

.pub-venue {
  font-style: italic;
  color: var(--text-secondary);
}

.pub-summary {
  color: var(--text-secondary);
}

.pub-note {
  font-size: var(--font-size-xs);
  color: var(--text-muted);
}

/* ============================================
   Footer
   ============================================ */
.site-footer {
  border-top: 1px solid var(--border-subtle);
  padding-top: var(--space-lg);
  font-size: var(--font-size-xs);
  color: var(--text-muted);
}

/* ============================================
   Mobile
   ============================================ */
@media (max-width: 40em) {
  .page {
    padding-top: var(--space-xl);
  }

  .intro {
    flex-direction: column-reverse;
    text-align: center;
    gap: var(--space-lg);
  }

  .intro-photo {
    flex-basis: auto;
  }

  .intro-photo img {
    width: 10rem;
    height: 10rem;
  }

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

  .pub {
    flex-direction: column;
  }

  .pub-media {
    flex-basis: auto;
  }
}