/* ----
   Academic Portfolio - Ruiqian (Richie) Li
   Design: Editorial/Scholarly with warmth
---- */

/* ----
   CSS Variables & Base
---- */
:root {
  --color-bg: #FDFBF7;
  --color-bg-alt: #F5F1EA;
  --color-text: #2C3E50;
  --color-text-light: #5D6D7E;
  --color-primary: #1B3A4B;
  --color-accent: #C45C3E;
  --color-accent-light: #E8D5CE;
  --color-border: #D5CFC5;
  
  --font-display: 'Libre Baskerville', Georgia, serif;
  --font-body: 'Source Sans 3', 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 6rem;
  
  --max-width: 1100px;
  --transition: 0.3s ease;
}

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

html {
  font-size: 18px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* Subtle paper texture overlay */
body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  opacity: 0.03;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%' height='100%' filter='url(%23noise)'/%3E%3C/svg%3E");
  z-index: 9999;
}

::selection {
  background: var(--color-accent-light);
  color: var(--color-primary);
}

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

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

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

/* ----
   Typography
---- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 400;
  line-height: 1.3;
  color: var(--color-primary);
}

h1 {
  font-size: 2.8rem;
  letter-spacing: -0.02em;
}

h2 {
  font-size: 1.8rem;
  margin-bottom: var(--space-md);
  position: relative;
  display: inline-block;
}

h2::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 40px;
  height: 2px;
  background: var(--color-accent);
}

h3 {
  font-size: 1.3rem;
  margin-bottom: var(--space-sm);
}

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

.lead {
  font-size: 1.15rem;
  color: var(--color-text-light);
  line-height: 1.8;
}

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

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

section:nth-child(even) {
  background: var(--color-bg-alt);
}

/* ----
   Header & Navigation
---- */
header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(253, 251, 247, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
  transition: var(--transition);
}

header.scrolled {
  box-shadow: 0 2px 20px rgba(0,0,0,0.06);
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-sm) var(--space-md);
  max-width: var(--max-width);
  margin: 0 auto;
}

.logo {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--color-primary);
  font-weight: 400;
}

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

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

.nav-links a {
  color: var(--color-text);
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  position: relative;
  padding-bottom: 4px;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background: var(--color-accent);
  transition: var(--transition);
}

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

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

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

/* ----
   Hero Section
---- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 80px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 60%;
  height: 150%;
  background: radial-gradient(ellipse, var(--color-accent-light) 0%, transparent 70%);
  opacity: 0.4;
  z-index: -1;
}

.hero-content {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: var(--space-lg);
  align-items: center;
}

.hero-text {
  animation: fadeInUp 0.8s ease-out;
}

.hero-subtitle {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: var(--space-sm);
}

.hero h1 {
  margin-bottom: var(--space-sm);
}

.hero-affiliation {
  font-size: 1.1rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-md);
}

.hero-affiliation a {
  color: var(--color-primary);
  border-bottom: 1px solid var(--color-border);
}

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

.hero-bio {
  font-size: 1.05rem;
  max-width: 540px;
  margin-bottom: var(--space-md);
}

.hero-photo {
  position: relative;
  animation: fadeIn 1s ease-out 0.3s both;
}

.hero-photo img {
  width: 100%;
  aspect-ratio: 3/4;
  object-fit: cover;
  border-radius: 4px;
  filter: grayscale(15%);
  transition: var(--transition);
}

.hero-photo:hover img {
  filter: grayscale(0%);
}

.hero-photo::before {
  content: '';
  position: absolute;
  top: 12px;
  left: 12px;
  right: -12px;
  bottom: -12px;
  border: 2px solid var(--color-accent);
  border-radius: 4px;
  z-index: -1;
}

/* ----
   Social Links
---- */
.social-links {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.social-links a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--color-text);
}

.social-links a:hover {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
}

.social-links svg {
  width: 16px;
  height: 16px;
}

/* ----
   Research Section
---- */
.research-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-md);
  margin-top: var(--space-md);
}

.research-card {
  padding: var(--space-md);
  background: white;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  transition: var(--transition);
}

.research-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0,0,0,0.08);
}

.research-card h3 {
  color: var(--color-primary);
}

.research-card p {
  color: var(--color-text-light);
  font-size: 0.95rem;
}

/* ----
   Publications Section
---- */
.publication-list {
  margin-top: var(--space-md);
}

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

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

.publication-year {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--color-accent);
  margin-bottom: var(--space-xs);
}

.publication-title {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--color-primary);
  margin-bottom: var(--space-xs);
  line-height: 1.4;
}

.publication-title a {
  color: inherit;
}

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

.publication-authors {
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-xs);
}

.publication-venue {
  font-size: 0.9rem;
  font-style: italic;
  color: var(--color-text-light);
}

.publication-badge {
  display: inline-block;
  padding: 4px 10px;
  background: var(--color-accent-light);
  color: var(--color-accent);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 3px;
  margin-top: var(--space-xs);
}

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

.publication-links a {
  font-size: 0.85rem;
  margin-right: var(--space-sm);
  color: var(--color-text-light);
}

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

/* ----
   Contact Section
---- */
.contact-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  margin-top: var(--space-md);
}

.contact-info p {
  margin-bottom: var(--space-sm);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.contact-info svg {
  width: 20px;
  height: 20px;
  color: var(--color-accent);
}

/* ----
   Footer
---- */
footer {
  padding: var(--space-md) 0;
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-light);
  border-top: 1px solid var(--color-border);
}

/* ----
   CV Page Styles
---- */
.page-header {
  padding: 140px 0 var(--space-lg);
  background: var(--color-bg-alt);
  text-align: center;
}

.page-header h1 {
  margin-bottom: var(--space-sm);
}

.page-header .lead {
  max-width: 600px;
  margin: 0 auto;
}

.cv-download {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: var(--space-md);
  padding: 12px 24px;
  background: var(--color-primary);
  color: white;
  border-radius: 4px;
  font-size: 0.9rem;
}

.cv-download:hover {
  background: var(--color-accent);
  color: white;
}

.cv-section {
  padding: var(--space-lg) 0;
  border-bottom: 1px solid var(--color-border);
}

.cv-section:last-child {
  border-bottom: none;
}

.cv-section h2 {
  margin-bottom: var(--space-md);
}

.cv-entry {
  display: grid;
  grid-template-columns: 140px 1fr;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.cv-entry:last-child {
  margin-bottom: 0;
}

.cv-date {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--color-text-light);
}

.cv-details h3 {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 4px;
}

.cv-details .institution {
  color: var(--color-accent);
  font-size: 0.95rem;
}

.cv-details p {
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-top: 4px;
}

/* ----
   Blog Page Styles
---- */
.blog-grid {
  display: grid;
  gap: var(--space-md);
  margin-top: var(--space-md);
}

.blog-card {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: var(--space-md);
  padding: var(--space-md);
  background: white;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  transition: var(--transition);
}

.blog-card:hover {
  transform: translateX(8px);
  border-color: var(--color-accent);
}

.blog-card-image {
  aspect-ratio: 4/3;
  background: var(--color-bg-alt);
  border-radius: 4px;
  overflow: hidden;
}

.blog-card-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.blog-card-content {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.blog-card-date {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--color-accent);
  margin-bottom: var(--space-xs);
}

.blog-card-title {
  font-family: var(--font-display);
  font-size: 1.2rem;
  color: var(--color-primary);
  margin-bottom: var(--space-xs);
  line-height: 1.4;
}

.blog-card-title a {
  color: inherit;
}

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

.blog-card-excerpt {
  font-size: 0.9rem;
  color: var(--color-text-light);
}

.blog-card-tags {
  display: flex;
  gap: 8px;
  margin-top: var(--space-sm);
}

.blog-card-tags span {
  font-size: 0.75rem;
  padding: 4px 10px;
  background: var(--color-bg-alt);
  border-radius: 20px;
  color: var(--color-text-light);
}

/* Blog post page */
.blog-post {
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-lg) var(--space-md);
}

.blog-post-header {
  padding-top: 120px;
  margin-bottom: var(--space-lg);
  text-align: center;
}

.blog-post-header h1 {
  font-size: 2.2rem;
  margin-bottom: var(--space-sm);
}

.blog-post-meta {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--color-text-light);
}

.blog-post-content {
  font-size: 1.05rem;
}

.blog-post-content p {
  margin-bottom: var(--space-md);
}

.blog-post-content h2 {
  margin-top: var(--space-lg);
  margin-bottom: var(--space-sm);
}

.blog-post-content blockquote {
  border-left: 3px solid var(--color-accent);
  padding-left: var(--space-md);
  margin: var(--space-md) 0;
  font-style: italic;
  color: var(--color-text-light);
}

/* ----
   Animations
---- */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ----
   Responsive Design
---- */
@media (max-width: 900px) {
  html {
    font-size: 16px;
  }
  
  .hero-content {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .hero-photo {
    max-width: 250px;
    margin: 0 auto var(--space-md);
    order: -1;
  }
  
  .hero-bio {
    margin-left: auto;
    margin-right: auto;
  }
  
  .social-links {
    justify-content: center;
  }
  
  .contact-content {
    grid-template-columns: 1fr;
  }
  
  .cv-entry {
    grid-template-columns: 1fr;
    gap: var(--space-xs);
  }
  
  .blog-card {
    grid-template-columns: 1fr;
  }
  
  .blog-card-image {
    height: 180px;
  }
}

@media (max-width: 600px) {
  h1 {
    font-size: 2rem;
  }
  
  h2 {
    font-size: 1.5rem;
  }
  
  section {
    padding: var(--space-lg) 0;
  }
  
  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-bg);
    padding: var(--space-md);
    border-bottom: 1px solid var(--color-border);
    gap: var(--space-sm);
  }
  
  .nav-links.active {
    display: flex;
  }
  
  .menu-toggle {
    display: flex;
  }
  
  .research-grid {
    grid-template-columns: 1fr;
  }
}