/* ===================================
   Geng Lab Academic Website
   Clean & Elegant Academic Style
   =================================== */

/* CSS Variables */
:root {
  /* Colors - Sophisticated academic palette */
  --color-primary: #1a365d;      /* Deep navy */
  --color-secondary: #2c5282;    /* Royal blue */
  --color-accent: #c9a227;       /* Academic gold */
  --color-text: #2d3748;         /* Dark gray */
  --color-text-light: #718096;   /* Medium gray */
  --color-bg: #ffffff;
  --color-bg-alt: #f7fafc;       /* Very light gray-blue */
  --color-border: #e2e8f0;
  
  /* Typography */
  --font-heading: "Noto Serif JP", "Times New Roman", serif;
  --font-body: "Noto Sans JP", "Helvetica Neue", sans-serif;
  --font-mono: "JetBrains Mono", monospace;
  
  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 4rem;
  
  /* Transitions */
  --transition: 0.3s ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  line-height: 1.4;
  color: var(--color-primary);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 1.875rem; margin-bottom: var(--space-lg); }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
  margin-bottom: var(--space-md);
}

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

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

/* Layout */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section {
  padding: var(--space-xl) 0;
}

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

/* Header & Navigation */
.header {
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-md) var(--space-lg);
  max-width: 1200px;
  margin: 0 auto;
}

.logo {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-primary);
}

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

.nav {
  display: flex;
  gap: var(--space-lg);
}

.nav a {
  color: var(--color-text);
  font-size: 0.9375rem;
  font-weight: 500;
  padding: var(--space-sm) 0;
  position: relative;
}

.nav a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width var(--transition);
}

.nav a:hover::after,
.nav a.active::after {
  width: 100%;
}

/* Mobile Menu */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-primary);
  margin: 5px 0;
  transition: var(--transition);
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
  color: white;
  padding: var(--space-xl) 0;
  text-align: center;
}

.hero h1 {
  color: white;
  font-size: 2rem;
  margin-bottom: var(--space-md);
}

.hero-subtitle {
  font-size: 1.125rem;
  opacity: 0.9;
  max-width: 800px;
  margin: 0 auto;
  line-height: 1.9;
}

.hero-affiliation {
  margin-top: var(--space-lg);
  font-size: 0.9375rem;
  opacity: 0.8;
}

/* Research Topics */
.research-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-lg);
}

.research-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  overflow: hidden;
  transition: transform var(--transition), box-shadow var(--transition);
}

.research-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.1);
}

.research-card-image {
  width: 100%;
  height: 200px;
  object-fit: cover;
  background: var(--color-bg-alt);
}

.research-card-content {
  padding: var(--space-lg);
}

.research-card h3 {
  font-size: 1.125rem;
  margin-bottom: var(--space-md);
  line-height: 1.6;
}

.research-card p {
  font-size: 0.9375rem;
  color: var(--color-text-light);
  line-height: 1.8;
}

/* Publications */
.publication-section {
  margin-bottom: var(--space-xl);
}

.publication-section h3 {
  font-size: 1.25rem;
  padding-bottom: var(--space-sm);
  border-bottom: 2px solid var(--color-accent);
  margin-bottom: var(--space-lg);
}

.publication-list {
  list-style: none;
}

.publication-item {
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--color-border);
  display: flex;
  gap: var(--space-md);
}

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

.publication-number {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  color: var(--color-accent);
  font-weight: 600;
  min-width: 2rem;
}

.publication-content {
  flex: 1;
}

.publication-authors {
  font-size: 0.9375rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-xs);
}

.publication-title {
  font-weight: 500;
  margin-bottom: var(--space-xs);
}

.publication-venue {
  font-style: italic;
  font-size: 0.9375rem;
  color: var(--color-text-light);
}

.publication-links {
  margin-top: var(--space-sm);
}

.publication-links a {
  font-size: 0.8125rem;
  margin-right: var(--space-md);
  color: var(--color-secondary);
}

/* Members */
.members-section {
  margin-bottom: var(--space-xl);
}

.members-section h3 {
  font-size: 1.25rem;
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-sm);
  border-bottom: 2px solid var(--color-accent);
}

.member-card {
  display: flex;
  gap: var(--space-lg);
  padding: var(--space-lg);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  margin-bottom: var(--space-md);
}

.member-photo {
  width: 120px;
  height: 150px;
  object-fit: cover;
  border-radius: 4px;
  background: var(--color-bg-alt);
}

.member-info h4 {
  margin-bottom: var(--space-xs);
}

.member-info .title {
  color: var(--color-accent);
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: var(--space-sm);
}

.member-info p {
  font-size: 0.9375rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-xs);
}

.member-links {
  margin-top: var(--space-md);
  display: flex;
  gap: var(--space-md);
}

.member-links a {
  font-size: 0.8125rem;
}

/* News */
.news-list {
  list-style: none;
}

.news-item {
  padding: var(--space-lg);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  gap: var(--space-lg);
}

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

.news-date {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  color: var(--color-accent);
  min-width: 100px;
}

.news-content h4 {
  margin-bottom: var(--space-sm);
  font-size: 1.0625rem;
}

.news-content p {
  font-size: 0.9375rem;
  color: var(--color-text-light);
}

.news-tag {
  display: inline-block;
  padding: 2px 8px;
  background: var(--color-primary);
  color: white;
  font-size: 0.75rem;
  border-radius: 4px;
  margin-right: var(--space-sm);
}

/* About / Profile */
.about-grid {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: var(--space-xl);
  align-items: start;
}

.about-photo {
  width: 100%;
  border-radius: 8px;
}

.about-content h3 {
  margin-top: var(--space-lg);
  margin-bottom: var(--space-md);
  font-size: 1.125rem;
}

.about-content ul {
  padding-left: var(--space-lg);
}

.about-content li {
  margin-bottom: var(--space-sm);
}

/* Footer */
.footer {
  background: var(--color-primary);
  color: white;
  padding: var(--space-xl) 0 var(--space-lg);
}

.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
  text-align: center;
}

.footer-info {
  margin-bottom: var(--space-lg);
}

.footer-info h4 {
  color: white;
  margin-bottom: var(--space-md);
}

.footer-info p {
  opacity: 0.8;
  font-size: 0.9375rem;
}

.footer-copyright {
  font-size: 0.875rem;
  opacity: 0.6;
  padding-top: var(--space-lg);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}

/* Responsive */
@media (max-width: 768px) {
  html {
    font-size: 15px;
  }
  
  .header-inner {
    padding: var(--space-md);
  }
  
  .menu-toggle {
    display: block;
  }
  
  .nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: var(--space-md);
    border-bottom: 1px solid var(--color-border);
    gap: 0;
  }
  
  .nav.active {
    display: flex;
  }
  
  .nav a {
    padding: var(--space-md);
    border-bottom: 1px solid var(--color-border);
  }
  
  .hero h1 {
    font-size: 1.5rem;
  }
  
  .research-grid {
    grid-template-columns: 1fr;
  }
  
  .about-grid {
    grid-template-columns: 1fr;
  }
  
  .about-photo {
    max-width: 200px;
  }
  
  .member-card {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }
  
  .news-item {
    flex-direction: column;
    gap: var(--space-sm);
  }
  
  .publication-item {
    flex-direction: column;
    gap: var(--space-sm);
  }
}

/* Utility Classes */
.text-center { text-align: center; }
.mt-lg { margin-top: var(--space-lg); }
.mb-lg { margin-bottom: var(--space-lg); }