/* ============================================
   ACADEMIC WEBSITE - STYLE SYSTEM
   Minimalist design for Jing Lin's academic profile
   ============================================ */

/* ---------- CSS Variables ---------- */
:root {
  /* Colors */
  --color-primary: #1a365d;
  --color-primary-light: #2c5282;
  --color-accent: #2b6cb0;
  --color-text: #2d3748;
  --color-text-light: #718096;
  --color-bg: #ffffff;
  --color-bg-alt: #f7fafc;
  --color-border: #e2e8f0;
  
  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-serif: 'Source Serif Pro', Georgia, serif;
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  
  /* Layout */
  --max-width: 800px;
  --nav-height: 60px;
  
  /* Transitions */
  --transition: 0.2s ease;
}

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

html {
  scroll-behavior: smooth;
}

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

/* ---------- Typography ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  color: var(--color-primary);
  line-height: 1.3;
}

h1 {
  font-size: 2.25rem;
  margin-bottom: var(--spacing-sm);
}

h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-xs);
  border-bottom: 2px solid var(--color-border);
}

h3 {
  font-size: 1.125rem;
  margin-bottom: var(--spacing-sm);
}

p {
  margin-bottom: var(--spacing-sm);
}

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

a:hover {
  color: var(--color-primary);
  text-decoration: underline;
}

/* ---------- Navigation ---------- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
}

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

.nav-logo {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-primary);
  text-decoration: none;
}

.nav-logo:hover {
  text-decoration: none;
  color: var(--color-accent);
}

.nav-links {
  display: flex;
  gap: var(--spacing-lg);
  list-style: none;
}

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

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

.nav-links a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.nav-links a:hover::after {
  width: 100%;
}

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

.nav-links a.active::after {
  width: 100%;
}

/* Mobile menu button */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-xs);
}

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

/* ---------- Main Content ---------- */
.main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: calc(var(--nav-height) + var(--spacing-xl)) var(--spacing-md) var(--spacing-2xl);
  min-height: 100vh;
}

/* ---------- Home Page - Profile ---------- */
.profile {
  text-align: center;
  padding: var(--spacing-xl) 0;
}

.profile-photo {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--color-bg-alt);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
  margin-bottom: var(--spacing-md);
}

.profile-name {
  font-size: 2rem;
  margin-bottom: var(--spacing-xs);
}

.profile-name-cn {
  font-size: 1.25rem;
  color: var(--color-text-light);
  font-weight: 400;
  margin-left: var(--spacing-xs);
}

.profile-title {
  font-size: 1.125rem;
  color: var(--color-text-light);
  margin-bottom: var(--spacing-xs);
}

.profile-institution {
  font-size: 1rem;
  color: var(--color-accent);
  font-weight: 500;
}

.profile-links {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
  flex-wrap: wrap;
}

.profile-links a {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-xs) var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  color: var(--color-text);
  transition: all var(--transition);
}

.profile-links a:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  text-decoration: none;
}

.profile-links svg {
  width: 18px;
  height: 18px;
}

/* Bio section */
.bio {
  margin-top: var(--spacing-xl);
  text-align: left;
}

.bio p {
  font-size: 1.0625rem;
}

/* ---------- Research Page ---------- */
.research-intro {
  margin-bottom: var(--spacing-xl);
}

.research-areas {
  display: grid;
  gap: var(--spacing-lg);
}

.research-card {
  padding: var(--spacing-lg);
  background: var(--color-bg-alt);
  border-radius: 8px;
  border-left: 3px solid var(--color-accent);
}

.research-card h3 {
  margin-bottom: var(--spacing-sm);
}

.research-card p {
  color: var(--color-text-light);
  margin-bottom: var(--spacing-sm);
}

.research-keywords {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-top: var(--spacing-sm);
}

.keyword {
  font-size: 0.8125rem;
  padding: 0.25rem 0.75rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 20px;
  color: var(--color-text-light);
}

/* ---------- Publications Page ---------- */
.publications-section {
  margin-bottom: var(--spacing-xl);
}

.publications-section h2 {
  font-size: 1.25rem;
}

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

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

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

.publication-title {
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--spacing-xs);
  line-height: 1.4;
}

.publication-title a {
  color: inherit;
}

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

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

.publication-authors .highlight {
  color: var(--color-text);
  font-weight: 500;
}

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

.publication-links {
  margin-top: var(--spacing-xs);
  display: flex;
  gap: var(--spacing-sm);
}

.publication-links a {
  font-size: 0.8125rem;
  padding: 0.25rem 0.5rem;
  background: var(--color-bg-alt);
  border-radius: 4px;
}

/* ---------- Contact Page ---------- */
.contact-section {
  padding: var(--spacing-xl) 0;
}

.contact-info {
  display: grid;
  gap: var(--spacing-lg);
}

.contact-item {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-md);
}

.contact-icon {
  width: 24px;
  height: 24px;
  color: var(--color-accent);
  flex-shrink: 0;
  margin-top: 2px;
}

.contact-item h3 {
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-light);
  margin-bottom: var(--spacing-xs);
}

.contact-item p,
.contact-item a {
  font-size: 1.0625rem;
}

/* ---------- Footer ---------- */
.footer {
  text-align: center;
  padding: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
  color: var(--color-text-light);
  font-size: 0.875rem;
}

/* ---------- Responsive Design ---------- */
@media (max-width: 768px) {
  :root {
    --nav-height: 56px;
  }
  
  h1 {
    font-size: 1.75rem;
  }
  
  h2 {
    font-size: 1.25rem;
  }
  
  .nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: var(--spacing-md);
    gap: 0;
    border-bottom: 1px solid var(--color-border);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  }
  
  .nav-links.active {
    display: flex;
  }
  
  .nav-links li {
    border-bottom: 1px solid var(--color-border);
  }
  
  .nav-links li:last-child {
    border-bottom: none;
  }
  
  .nav-links a {
    display: block;
    padding: var(--spacing-sm) 0;
  }
  
  .nav-toggle {
    display: block;
  }
  
  .profile-photo {
    width: 120px;
    height: 120px;
  }
  
  .profile-name {
    font-size: 1.5rem;
  }
  
  .profile-links {
    flex-direction: column;
    align-items: center;
  }
  
  .profile-links a {
    width: 100%;
    max-width: 280px;
    justify-content: center;
  }
}

/* ---------- Print Styles ---------- */
@media print {
  .nav,
  .nav-toggle {
    display: none;
  }
  
  .main {
    padding-top: 0;
  }
  
  a {
    color: var(--color-text);
  }
  
  a::after {
    content: " (" attr(href) ")";
    font-size: 0.8em;
  }
}