:root {
  --penn-blue: #011F5B;
  --penn-red: #990000;
  --penn-blue-light: #1a3a7a;
  --penn-blue-bg: #e8eef7;
  --gray-50: #f8f9fa;
  --gray-100: #f0f1f3;
  --gray-200: #e2e4e8;
  --gray-300: #c5c8d0;
  --gray-600: #6b7280;
  --gray-700: #4a4f5a;
  --gray-800: #2d3138;
  --gray-900: #1a1d23;
  --white: #ffffff;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --radius: 8px;
  --transition: 0.2s ease;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  color: var(--gray-800);
  line-height: 1.6;
  background: var(--white);
}

a { color: var(--penn-blue); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--penn-red); }

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

/* ===== NAVBAR ===== */
.navbar {
  background: var(--penn-blue);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow-md);
}

.navbar .container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.navbar-brand {
  color: var(--white) !important;
  font-size: 1.35rem;
  font-weight: 700;
  padding: 16px 0;
  letter-spacing: -0.02em;
}

.navbar-brand span {
  font-weight: 400;
  font-size: 0.85rem;
  opacity: 0.8;
  display: block;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 4px;
}

.nav-links a {
  color: rgba(255,255,255,0.85);
  padding: 10px 18px;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--white);
  background: rgba(255,255,255,0.12);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: white;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 8px;
}

/* ===== LAYOUT ===== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

.page-header {
  background: linear-gradient(135deg, var(--penn-blue) 0%, var(--penn-blue-light) 100%);
  color: var(--white);
  padding: 48px 0;
  margin-bottom: 48px;
}

.page-header h1 {
  font-size: 2.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.page-header p {
  font-size: 1.1rem;
  opacity: 0.85;
  margin-top: 8px;
}

section {
  margin-bottom: 80px;
  margin-top: 0;
}

main > section:first-child {
  margin-top: 48px;
}

section h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--penn-blue);
  margin-top: 16px;
  margin-bottom: 28px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--gray-200);
}

section h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--gray-800);
  margin-bottom: 16px;
}

/* ===== HOME: HERO ===== */
.hero {
  background: var(--penn-blue);
  color: var(--white);
  padding: 160px 0 140px;
  position: relative;
  overflow: hidden;
}

.hero-slideshow {
  position: absolute;
  top: 0; right: 0; bottom: 0; left: 0;
}

.hero-slide {
  position: absolute;
  top: 0; left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0;
  transition: opacity 1s ease;
}

.hero-slide.active {
  opacity: 1;
}

.hero-overlay {
  position: absolute;
  top: 0; right: 0; bottom: 0; left: 0;
  background: rgba(1, 31, 91, 0.65);
  z-index: 1;
}

.hero .container { position: relative; z-index: 1; }

.hero h1 {
  font-size: 2.75rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 12px;
}

.hero .subtitle {
  font-size: 1.25rem;
  opacity: 0.85;
  font-weight: 400;
  margin-bottom: 8px;
}

.hero .affiliation {
  font-size: 1rem;
  opacity: 0.7;
}

/* ===== HOME: GROUP PHOTO CAROUSEL ===== */
.group-carousel {
  position: relative;
  margin: 48px 0;
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.carousel-track {
  display: flex;
  transition: transform 0.5s ease;
}

.carousel-track img {
  width: 100%;
  flex-shrink: 0;
  object-fit: cover;
  aspect-ratio: 16/7;
}

.carousel-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  background: rgba(0,0,0,0.5);
  color: white;
  border: none;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  font-size: 1.2rem;
  cursor: pointer;
  transition: background var(--transition);
  z-index: 2;
}

.carousel-btn:hover { background: rgba(0,0,0,0.7); }
.carousel-btn.prev { left: 16px; }
.carousel-btn.next { right: 16px; }

.carousel-dots {
  position: absolute;
  bottom: 16px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  gap: 8px;
  z-index: 2;
}

.carousel-dots button {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  border: 2px solid white;
  background: transparent;
  cursor: pointer;
  transition: background var(--transition);
}

.carousel-dots button.active { background: white; }

/* ===== HOME: NEWS / HIGHLIGHTS ===== */
.highlights-grid-section {
  margin-top: 0;
}

.highlights-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 24px;
}

.highlight-card {
  background: var(--penn-blue-bg);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 28px;
  transition: all var(--transition);
}

.highlight-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--penn-blue);
}

.highlight-card .venue {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--penn-red);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 8px;
}

.highlight-card h3 {
  font-size: 1.05rem;
  line-height: 1.4;
  margin-bottom: 8px;
  color: var(--gray-900);
}

.highlight-card .authors {
  font-size: 0.88rem;
  color: var(--gray-600);
  margin-bottom: 12px;
}

.highlight-card .links a {
  font-size: 0.82rem;
  font-weight: 600;
  margin-right: 16px;
  padding: 4px 0;
}

/* ===== NEWS SECTION ===== */
.news-list {
  list-style: none;
}

.news-list li {
  padding: 16px 0;
  border-bottom: 1px solid var(--gray-100);
  display: flex;
  gap: 16px;
}

.news-list .date {
  font-size: 0.85rem;
  color: var(--gray-600);
  min-width: 100px;
  font-weight: 500;
}

/* ===== PEOPLE ===== */
.people-section { margin-bottom: 48px; }

.pi-card {
  display: flex;
  gap: 36px;
  align-items: flex-start;
  background: var(--gray-50);
  padding: 36px;
  border-radius: var(--radius);
  margin-bottom: 36px;
}

.pi-card img {
  width: 200px;
  height: 250px;
  object-fit: cover;
  border-radius: var(--radius);
  flex-shrink: 0;
}

.pi-card h3 { font-size: 1.5rem; margin-bottom: 4px; color: var(--penn-blue); }
.pi-card .role { color: var(--gray-600); margin-bottom: 12px; }

.people-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 24px;
}

.person-card {
  text-align: center;
}

.person-card img {
  width: 140px;
  height: 175px;
  object-fit: cover;
  border-radius: var(--radius);
  margin: 0 auto 12px;
  box-shadow: var(--shadow-sm);
}

.person-card .name {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--gray-800);
}

.person-card .dept {
  font-size: 0.8rem;
  color: var(--gray-600);
}

.alumni-list {
  column-count: 2;
  column-gap: 48px;
  list-style: none;
}

.alumni-list li {
  padding: 4px 0;
  padding-left: 16px;
  position: relative;
  font-size: 0.9rem;
  break-inside: avoid;
}

.alumni-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 6px;
  height: 6px;
  background: var(--penn-blue);
  border-radius: 50%;
}

/* ===== RESEARCH TOPICS ===== */
.research-topics-section h2 {
  text-align: center;
  font-size: 1.75rem;
  border-bottom: none;
  margin-bottom: 20px;
}

.research-category-tabs {
  display: flex;
  gap: 0;
  border-bottom: 2px solid var(--gray-200);
  margin-bottom: 0;
}

.research-category-tab {
  padding: 12px 24px;
  background: none;
  border: none;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--gray-600);
  cursor: pointer;
  position: relative;
  transition: color var(--transition), border-bottom-color 0.3s ease;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
}

.research-category-tab:hover {
  color: var(--penn-blue);
}

.research-category-tab.active {
  color: var(--penn-blue);
  border-bottom-color: var(--penn-blue);
}

.research-category-panel {
  display: none;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.4s ease, transform 0.4s ease;
}

.research-category-panel.active {
  display: block;
  opacity: 1;
  transform: translateY(0);
}

.research-category-panel.fade-out {
  display: block;
  opacity: 0;
  transform: translateY(-12px);
}

.research-topic-item {
  padding: 28px 0;
  border-bottom: 1px solid var(--gray-200);
  animation: fadeSlideUp 0.5s ease both;
}

.research-topic-item:nth-child(1) { animation-delay: 0s; }
.research-topic-item:nth-child(2) { animation-delay: 0.08s; }
.research-topic-item:nth-child(3) { animation-delay: 0.16s; }
.research-topic-item:nth-child(4) { animation-delay: 0.24s; }
.research-topic-item:nth-child(5) { animation-delay: 0.32s; }

@keyframes fadeSlideUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

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

.research-topic-item h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 12px;
}

.research-topic-item p {
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--gray-700);
  margin-bottom: 16px;
}

.view-pubs-btn {
  display: inline-block;
  padding: 8px 18px;
  border: 1.5px solid var(--penn-blue);
  border-radius: 6px;
  background: var(--white);
  color: var(--penn-blue);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
}

.view-pubs-btn:hover {
  background: var(--penn-blue);
  color: var(--white);
}

/* ===== RESEARCH / PUBLICATIONS ===== */
#publications-section.highlight {
  animation: highlightPulse 0.8s ease;
}

@keyframes highlightPulse {
  0% { background: transparent; }
  30% { background: var(--penn-blue-bg); }
  100% { background: transparent; }
}

.topic-hint {
  font-size: 0.85rem;
  color: var(--gray-600);
  margin-bottom: 12px;
}

.topic-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--gray-200);
}

.topic-tab {
  padding: 8px 16px;
  border: 1px solid var(--gray-300);
  border-radius: 20px;
  background: var(--white);
  color: var(--gray-700);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
}

.topic-tab:hover {
  border-color: var(--penn-blue);
  color: var(--penn-blue);
}

.topic-tab.active {
  background: var(--penn-blue);
  color: var(--white);
  border-color: var(--penn-blue);
}

#publications-container {
  transition: opacity 0.3s ease;
}

#publications-container.fade-out {
  opacity: 0;
}

.pub-year-group {
  animation: fadeSlideUp 0.4s ease both;
}

.pub-year-group:nth-child(2) { animation-delay: 0.05s; }
.pub-year-group:nth-child(3) { animation-delay: 0.1s; }
.pub-year-group:nth-child(4) { animation-delay: 0.15s; }
.pub-year-group:nth-child(5) { animation-delay: 0.2s; }

.pub-year-group h3 {
  font-size: 1.2rem;
  color: var(--penn-blue);
  margin: 32px 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--gray-200);
}

.pub-entry {
  padding: 16px 0;
  border-bottom: 1px solid var(--gray-100);
}

.pub-entry:last-child { border-bottom: none; }

.pub-entry .pub-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--gray-900);
  margin-bottom: 4px;
}

.pub-entry .pub-authors {
  font-size: 0.88rem;
  color: var(--gray-600);
  margin-bottom: 4px;
}

.pub-entry .pub-venue {
  font-size: 0.85rem;
  color: var(--gray-700);
  font-style: italic;
}

.pub-entry .pub-links {
  margin-top: 6px;
}

.pub-entry .pub-links a {
  font-size: 0.8rem;
  font-weight: 600;
  margin-right: 12px;
  color: var(--penn-red);
}

.pub-type-badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--gray-100);
  color: var(--gray-600);
  margin-left: 8px;
  vertical-align: middle;
}

.pub-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  margin-top: 6px;
}

.pub-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 12px;
  cursor: pointer;
  transition: opacity 0.15s;
}

.pub-tag:hover {
  opacity: 0.8;
}

.pub-count {
  font-size: 0.9rem;
  color: var(--gray-600);
  margin-bottom: 16px;
}

.pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 32px;
}

.pagination button {
  padding: 8px 14px;
  border: 1px solid var(--gray-300);
  border-radius: var(--radius);
  background: var(--white);
  cursor: pointer;
  font-size: 0.85rem;
  transition: all var(--transition);
}

.pagination button:hover,
.pagination button.active {
  background: var(--penn-blue);
  color: var(--white);
  border-color: var(--penn-blue);
}

/* ===== TEACHING ===== */
.teaching-table {
  width: 100%;
  border-collapse: collapse;
}

.teaching-table th,
.teaching-table td {
  padding: 14px 16px;
  text-align: left;
  border-bottom: 1px solid var(--gray-200);
}

.teaching-table th {
  background: var(--gray-50);
  font-weight: 600;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--gray-600);
}

.teaching-table td { font-size: 0.92rem; }

.teaching-table tr:hover td { background: var(--gray-50); }

/* ===== TALKS ===== */
.talks-group { margin-bottom: 40px; }

.talk-entry {
  padding: 14px 0;
  border-bottom: 1px solid var(--gray-100);
}

.talk-entry .talk-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--gray-900);
}

.talk-entry .talk-venue {
  font-size: 0.88rem;
  color: var(--gray-600);
  margin-top: 2px;
}

.talk-entry .talk-date {
  font-size: 0.82rem;
  color: var(--gray-600);
}

/* ===== FOOTER ===== */
.footer {
  background: var(--gray-900);
  color: rgba(255,255,255,0.7);
  padding: 48px 0 32px;
  margin-top: 80px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 32px;
}

.footer h4 {
  color: var(--white);
  font-size: 1rem;
  margin-bottom: 16px;
}

.footer p, .footer li { font-size: 0.88rem; line-height: 1.8; }
.footer ul { list-style: none; }
.footer a { color: rgba(255,255,255,0.7); }
.footer a:hover { color: var(--white); }

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 24px;
  text-align: center;
  font-size: 0.82rem;
}

/* ===== PROFILE PAGE ===== */
.profile-hero {
  display: flex;
  gap: 40px;
  align-items: flex-start;
  margin-bottom: 56px;
}

.profile-photo-col {
  flex-shrink: 0;
  display: flex;
  justify-content: center;
}

.profile-photo {
  width: 240px;
  height: 300px;
  object-fit: cover;
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  margin: 0 auto;
}

.profile-info-col {
  flex: 1;
}

.profile-name {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--penn-blue);
  margin-bottom: 16px;
  padding-bottom: 0;
  border-bottom: none;
}

.profile-titles {
  list-style: none;
  margin-bottom: 20px;
}

.profile-titles li {
  font-size: 0.95rem;
  color: var(--gray-700);
  padding: 3px 0;
  line-height: 1.5;
}

.profile-titles li:first-child {
  font-weight: 600;
  color: var(--gray-800);
}

.profile-contact {
  background: var(--gray-50);
  padding: 16px 20px;
  border-radius: var(--radius);
  border-left: 3px solid var(--penn-blue);
}

.profile-contact p {
  font-size: 0.92rem;
  margin-bottom: 4px;
  color: var(--gray-700);
}

.profile-contact p:last-child {
  margin-bottom: 0;
}

.profile-section {
  margin-bottom: 48px;
}

.profile-section h2 {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--penn-blue);
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--gray-200);
}

.profile-section p {
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--gray-700);
  margin-bottom: 12px;
}

.profile-section p:last-child {
  margin-bottom: 0;
}

.awards-list {
  list-style: none;
  column-count: 2;
  column-gap: 40px;
}

.awards-list li {
  padding: 6px 0;
  padding-left: 18px;
  position: relative;
  font-size: 0.92rem;
  color: var(--gray-700);
  break-inside: avoid;
}

.awards-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 6px;
  height: 6px;
  background: var(--penn-red);
  border-radius: 50%;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .nav-toggle { display: block; }

  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--penn-blue);
    flex-direction: column;
    padding: 8px 24px 16px;
    box-shadow: var(--shadow-md);
  }

  .nav-links.open { display: flex; }
  .nav-links a { padding: 12px 0; }

  .hero h1 { font-size: 2rem; }
  .hero .subtitle { font-size: 1rem; }

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

  .pi-card { flex-direction: column; align-items: center; text-align: center; }
  .pi-card img { width: 160px; height: 200px; }

  .people-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 16px; }

  .alumni-list { column-count: 1; }

  .research-category-tabs { flex-wrap: wrap; }
  .research-category-tab { padding: 10px 16px; font-size: 0.88rem; }

  .footer-grid { grid-template-columns: 1fr; gap: 24px; }

  .teaching-table { font-size: 0.85rem; }
  .teaching-table th, .teaching-table td { padding: 10px 8px; }

  .profile-hero { flex-direction: column; align-items: center; text-align: center; }
  .profile-photo { width: 200px; height: 250px; }
  .profile-contact { text-align: left; }
  .awards-list { column-count: 1; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 1.6rem; }
  .page-header h1 { font-size: 1.6rem; }
  .people-grid { grid-template-columns: repeat(2, 1fr); }
}