/* ============================================
   Fengze Xie - Academic Website
   Design: content-forward, video/figure emphasis
   ============================================ */

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

:root {
  --color-bg: #fafaf9;
  --color-bg-card: #ffffff;
  --color-bg-card-hover: #f5f5f3;
  --color-surface: #eeedeb;
  --color-text: #1a1a1a;
  --color-text-muted: #5a5f66;          /* darkened Cool Gray for readability */
  --color-accent: #003B4C;              /* PMS 548c — deep teal for links */
  --color-accent-soft: rgba(0, 59, 76, 0.06);
  --color-accent-glow: rgba(0, 59, 76, 0.10);
  --color-highlight: #FF6C0C;           /* Caltech Orange PMS 1585c */
  --color-conference: #005851;           /* PMS 3292c — deep green */
  --color-journal: #7A303F;             /* PMS 195c — deep maroon */
  --color-preprint: #644B78;            /* PMS 668c — deep purple */
  --color-award: #c45a00;              /* dark orange for text legibility */
  --color-border: rgba(0, 0, 0, 0.08);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-serif: 'Source Serif 4', 'Georgia', serif;
  --max-width: 1100px;
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

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

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

a:hover {
  color: #005851;
}

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

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

/* ---------- Navigation ---------- */
#navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(248, 249, 250, 0.85);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition), box-shadow var(--transition);
}

#navbar.scrolled {
  background: rgba(248, 249, 250, 0.97);
  box-shadow: 0 1px 8px rgba(0, 0, 0, 0.06);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-text) !important;
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 8px;
}

.nav-links a {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 6px 14px;
  border-radius: 6px;
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-text);
  background: var(--color-accent-soft);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: all var(--transition);
}

/* ---------- Hero ---------- */
#hero {
  padding: 140px 0 48px;
  min-height: auto;
}

.hero-content {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 60px;
  align-items: start;
}

.hero-text h1 {
  font-family: var(--font-serif);
  font-size: 3rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 8px;
  color: #003B4C;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--color-highlight);
  font-weight: 500;
  margin-bottom: 4px;
}

.inline-logo {
  display: inline-block;
  height: 1.1em;
  width: auto;
  vertical-align: middle;
  margin-left: 3px;
  border-radius: 2px;
}

.hero-logos {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 16px;
}

.hero-logo {
  height: 28px;
  width: auto;
  object-fit: contain;
  opacity: 0.85;
  transition: opacity var(--transition);
}

.hero-logo:hover {
  opacity: 1;
}

.hero-affiliation {
  font-size: 1rem;
  color: var(--color-text-muted);
  margin-bottom: 24px;
}

.hero-bio {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  line-height: 1.75;
  margin-bottom: 16px;
}

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

.hero-stats {
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--color-accent);
  margin-bottom: 16px;
  line-height: 1.6;
}

.hero-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 16px;
  margin-top: 28px;
  padding-top: 24px;
  border-top: 1px solid var(--color-border);
}

.email-display {
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 0.85rem;
  color: var(--color-text-muted);
  background: var(--color-surface);
  padding: 6px 14px;
  border-radius: 6px;
  border: 1px solid var(--color-border);
}

.icon-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-muted) !important;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  border: 1px solid var(--color-border);
  transition: all var(--transition);
}

.icon-link:hover {
  color: var(--color-accent) !important;
  border-color: var(--color-accent);
  background: var(--color-accent-soft);
}

.icon-link svg {
  flex-shrink: 0;
}

.hero-photo {
  position: relative;
}

.hero-photo img {
  width: 280px;
  height: 330px;
  object-fit: cover;
  object-position: center top;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.1);
}

/* ---------- Section Titles ---------- */
.section-title {
  font-family: var(--font-serif);
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 40px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--color-highlight);
  display: inline-block;
}

section {
  padding: 52px 0;
}

section:nth-child(even) {
  background: rgba(0, 0, 0, 0.015);
}

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

.news-list li {
  display: flex;
  gap: 20px;
  padding: 14px 0;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.925rem;
  line-height: 1.6;
}

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

.news-date {
  flex-shrink: 0;
  width: 90px;
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--color-highlight);
  letter-spacing: 0.02em;
  padding-top: 2px;
}

.news-text {
  color: var(--color-text-muted);
}

.news-text strong {
  color: var(--color-text);
}

/* ---------- Research Overview ---------- */
.research-overview {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  line-height: 1.75;
  margin-bottom: 28px;
  max-width: 820px;
}

.research-overview em {
  color: var(--color-text);
  font-style: italic;
}

/* ---------- Research Directions Tabs ---------- */
.direction-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.direction-tab {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 8px 20px;
  border: 1.5px solid var(--color-border);
  border-radius: 100px;
  background: var(--color-bg);
  color: var(--color-text-muted);
  cursor: pointer;
  transition: var(--transition);
}

.direction-tab:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.direction-tab.active {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #fff;
}


/* ---------- Research Category Subheadings ---------- */
.research-category {
  font-family: var(--font-serif);
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-top: 40px;
  margin-bottom: 24px;
  padding-left: 4px;
  border-left: 3px solid var(--color-highlight);
  padding-left: 14px;
}

.research-category:first-of-type {
  margin-top: 0;
}

/* ---------- Project Cards ---------- */
.project-card {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  background: var(--color-bg-card);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  overflow: hidden;
  margin-bottom: 32px;
  transition: all var(--transition);
}

.project-card.first-author {
  border-left: 3px solid var(--color-highlight);
}

.project-card:hover {
  border-color: rgba(0, 59, 76, 0.15);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
  transform: translateY(-2px);
}

.project-media {
  position: relative;
  overflow: hidden;
  background: #f0efed;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 300px;
}

.project-media video {
  width: 100%;
  height: auto;
  object-fit: contain;
}

.project-media > img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  padding: 16px;
}

.project-media-stacked {
  flex-direction: column;
  align-items: stretch;
  padding: 0;
  gap: 0;
}

.project-media-stacked video {
  width: 100%;
  height: auto;
  border-radius: 0;
}

.media-supplement {
  width: 100%;
  padding: 10px 12px 12px;
  object-fit: contain;
}

.project-media-gallery {
  flex-direction: column;
  padding: 12px;
  gap: 8px;
}

.project-media-gallery .gallery-main {
  width: 100%;
  border-radius: var(--radius-sm);
  object-fit: contain;
  padding: 0;
}

.gif-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.gif-row img {
  width: 100%;
  border-radius: var(--radius-sm);
  background: #fff;
}

.triple-row {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 8px;
}

.triple-row img {
  width: 100%;
  border-radius: var(--radius-sm);
  background: #fff;
}

.dual-image {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  width: 100%;
}

.dual-image img {
  width: 100%;
  border-radius: var(--radius-sm);
  object-fit: cover;
}

.project-info {
  padding: 32px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.project-info h3 {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 10px;
  color: var(--color-text);
}

.authors {
  font-size: 0.925rem;
  color: var(--color-text-muted);
  margin-bottom: 12px;
  line-height: 1.6;
}

.project-desc {
  font-size: 0.925rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: 20px;
}

/* Venue badges */
.venue-badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: 4px;
  margin-bottom: 12px;
  margin-right: 6px;
}

.venue-badge.conference {
  background: rgba(0, 88, 81, 0.08);
  color: var(--color-conference);
  border: 1px solid rgba(0, 88, 81, 0.2);
}

.venue-badge.journal {
  background: rgba(122, 48, 63, 0.08);
  color: var(--color-journal);
  border: 1px solid rgba(122, 48, 63, 0.2);
}

.venue-badge.preprint {
  background: rgba(100, 75, 120, 0.08);
  color: var(--color-preprint);
  border: 1px solid rgba(100, 75, 120, 0.2);
}

.award-badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--color-award);
  background: rgba(196, 90, 0, 0.07);
  border: 1px solid rgba(196, 90, 0, 0.18);
  padding: 2px 8px;
  border-radius: 4px;
  margin-bottom: 8px;
  margin-right: 4px;
}

/* Project link buttons */
.project-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 7px 16px;
  border-radius: 6px;
  transition: all var(--transition);
  border: 1px solid;
}

.btn-paper {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background: var(--color-accent-soft);
}

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

.btn-video {
  color: var(--color-conference);
  border-color: var(--color-conference);
  background: rgba(0, 88, 81, 0.05);
}

.btn-video:hover {
  background: var(--color-conference);
  color: #fff;
}

.btn-web {
  color: var(--color-journal);
  border-color: var(--color-journal);
  background: rgba(122, 48, 63, 0.05);
}

.btn-web:hover {
  background: var(--color-journal);
  color: #fff;
}

.btn-code {
  color: var(--color-preprint);
  border-color: var(--color-preprint);
  background: rgba(100, 75, 120, 0.05);
}

.btn-code:hover {
  background: var(--color-preprint);
  color: #fff;
}

/* ---------- Publications ---------- */
.pub-category {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-accent);
  margin-bottom: 16px;
  margin-top: 32px;
}

.pub-category:first-of-type {
  margin-top: 0;
}

.pub-list {
  list-style: none;
  counter-reset: pub-counter;
  margin-bottom: 16px;
}

.pub-list li {
  counter-increment: pub-counter;
  position: relative;
  padding: 16px 20px 16px 48px;
  margin-bottom: 8px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--color-text-muted);
  transition: all var(--transition);
}

.pub-list li::before {
  content: counter(pub-counter) ".";
  position: absolute;
  left: 18px;
  top: 16px;
  font-weight: 700;
  color: var(--color-accent);
  font-size: 0.9rem;
}

.pub-list li:hover {
  border-color: rgba(0, 59, 76, 0.12);
  background: var(--color-bg-card-hover);
}

.pub-links a {
  font-weight: 600;
  font-size: 0.85rem;
  margin-left: 2px;
}

.pub-award {
  display: block;
  margin-top: 6px;
  font-size: 0.85rem;
  color: var(--color-award);
}

/* ---------- Teaching ---------- */
.teaching-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.teaching-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px;
  transition: all var(--transition);
}

.teaching-card:hover {
  border-color: rgba(0, 59, 76, 0.15);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.teaching-term {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-highlight);
  margin-bottom: 8px;
}

.teaching-card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 6px;
  line-height: 1.4;
}

.teaching-card h3 a {
  color: var(--color-text);
}

.teaching-card h3 a:hover {
  color: var(--color-accent);
}

.teaching-role {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-bottom: 14px;
}

.teaching-lectures {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.8;
}

.lecture-label {
  font-weight: 600;
  color: var(--color-text);
}

/* ---------- Awards ---------- */
.awards-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.award-item {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 14px 20px;
  border-radius: var(--radius-sm);
  background: var(--color-bg-card);
  border: 1px solid transparent;
  transition: all var(--transition);
}

.award-item:nth-child(odd) {
  background: rgba(0, 0, 0, 0.02);
}

.award-item:hover {
  background: var(--color-bg-card-hover);
  border-color: var(--color-border);
}

.award-name {
  font-size: 0.925rem;
  flex: 1;
  padding-right: 20px;
}

.award-year {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  font-weight: 500;
  white-space: nowrap;
}

/* ---------- Service ---------- */
.service-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
}

.service-block h3 {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-accent);
  margin-bottom: 16px;
}

.service-block ul {
  list-style: none;
}

.service-block li {
  position: relative;
  padding: 10px 0 10px 20px;
  font-size: 0.925rem;
  color: var(--color-text-muted);
  line-height: 1.7;
  border-left: 2px solid var(--color-border);
  margin-bottom: 8px;
}

.service-block li strong {
  color: var(--color-text);
}

/* ---------- Education ---------- */
.education-timeline {
  position: relative;
  padding-left: 52px;
}

.education-timeline::before {
  content: '';
  position: absolute;
  left: 17px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(to bottom, var(--color-highlight), var(--color-border));
}

.edu-item {
  display: flex;
  gap: 24px;
  margin-bottom: 32px;
  position: relative;
}

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

.edu-icon {
  position: absolute;
  left: -48px;
  top: 4px;
  width: 36px;
  height: 36px;
  background: var(--color-bg);
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

.edu-icon img {
  width: 36px;
  height: auto;
  object-fit: contain;
  border-radius: 3px;
}

.edu-content {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  flex: 1;
  transition: all var(--transition);
}

.edu-content:hover {
  border-color: rgba(0, 59, 76, 0.15);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.edu-dates {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-highlight);
  margin-bottom: 6px;
}

.edu-content h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 4px;
  color: var(--color-text);
}

.edu-content h3 a {
  color: var(--color-text);
}

.edu-content h3 a:hover {
  color: var(--color-accent);
}

.edu-degree {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.edu-detail {
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

/* ---------- Contact ---------- */
#contact {
  text-align: center;
}

.contact-content {
  max-width: 600px;
  margin: 0 auto;
}

.contact-message {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
  line-height: 1.7;
}

.contact-message strong {
  color: var(--color-highlight);
  font-weight: 700;
}

.contact-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 16px;
}

.contact-item {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  color: var(--color-text-muted);
  transition: all var(--transition);
}

.contact-item:hover {
  border-color: var(--color-accent);
  background: var(--color-accent-soft);
}

.contact-item svg {
  flex-shrink: 0;
  color: var(--color-accent);
}

.contact-item a {
  color: var(--color-text-muted);
}

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

/* ---------- Contact CTA ---------- */
#contact-cta {
  padding: 60px 0;
}

.cta-container {
  text-align: center;
  max-width: 640px;
}

.cta-text {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  line-height: 1.75;
  margin-bottom: 24px;
}

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

.cta-links {
  display: flex;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
}

.btn-cta {
  display: inline-block;
  padding: 10px 28px;
  background: var(--color-accent);
  color: #fff;
  border-radius: 100px;
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  transition: var(--transition);
}

.btn-cta:hover {
  background: #00506a;
}

.btn-cta-outline {
  display: inline-block;
  padding: 10px 28px;
  border: 1.5px solid var(--color-accent);
  color: var(--color-accent);
  border-radius: 100px;
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  transition: var(--transition);
}

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

/* ---------- Footer ---------- */
footer {
  padding: 40px 0;
  border-top: 1px solid var(--color-border);
  text-align: center;
}

footer p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* ---------- Scroll Animations (GSAP handles these, fallback for no-JS) ---------- */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* Ensure GSAP-animated elements are visible if JS loads */
.gsap-ready .fade-in {
  opacity: 1;
  transform: none;
}

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .hero-content {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .hero-photo {
    order: -1;
    text-align: center;
  }

  .hero-photo img {
    width: 200px;
    height: 240px;
    margin: 0 auto;
  }

  .hero-text h1 {
    font-size: 2.2rem;
  }

  .project-card {
    grid-template-columns: 1fr;
  }

  .project-media {
    min-height: 220px;
  }

  .teaching-grid,
  .service-grid {
    grid-template-columns: 1fr;
  }

  .education-timeline {
    padding-left: 48px;
  }
}

@media (max-width: 640px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(248, 249, 250, 0.98);
    backdrop-filter: blur(20px);
    flex-direction: column;
    padding: 16px 24px;
    border-bottom: 1px solid var(--color-border);
  }

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

  .nav-toggle {
    display: flex;
  }

  .hero-text h1 {
    font-size: 1.8rem;
  }

  .hero-links {
    gap: 10px;
  }

  .section-title {
    font-size: 1.6rem;
  }

  .project-info {
    padding: 20px;
  }

  .award-item {
    flex-direction: column;
    gap: 2px;
  }

  .direction-tab {
    font-size: 0.82rem;
    padding: 6px 14px;
  }

}