:root {
  --bg: #0a111f;
  --bg-elevated: #0f172a;
  --panel: rgba(255, 255, 255, 0.07);
  --panel-strong: rgba(255, 255, 255, 0.1);
  --line: rgba(255, 255, 255, 0.14);
  --line-strong: rgba(125, 211, 252, 0.35);
  /* Primary copy: ~15:1 on --bg */
  --text: #f1f5f9;
  /* Secondary: ~8:1 on --bg */
  --muted: #cbd5e1;
  /* Tertiary / captions: ~5.5:1 on --bg (small text) */
  --muted-2: #a8b8cc;
  --accent: #38bdf8;
  --accent-bright: #7dd3fc;
  --accent-on-dark: #e0f2fe;
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.35);
  --radius: 2rem;
  --max: 1280px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  text-decoration: none;
  color: inherit;
}

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

h1,
h2,
h3,
.hero h1,
.section-head h2,
.contact-panel h2 {
  color: var(--text);
}

.page-bg {
  position: fixed;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
  z-index: 0;
}

.glow {
  position: absolute;
  border-radius: 9999px;
  filter: blur(72px);
}

.glow-1 {
  top: -6rem;
  left: -4rem;
  width: 24rem;
  height: 24rem;
  background: rgba(14, 165, 233, 0.2);
}

.glow-2 {
  top: 16rem;
  right: -4rem;
  width: 30rem;
  height: 30rem;
  background: rgba(99, 102, 241, 0.16);
}

.glow-3 {
  bottom: 0;
  left: 33%;
  width: 20rem;
  height: 20rem;
  background: rgba(34, 211, 238, 0.14);
}

.container {
  width: min(var(--max), calc(100% - 3rem));
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--line);
  background: rgba(10, 17, 31, 0.92);
  backdrop-filter: blur(18px);
}

.nav-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 0;
}

.brand-kicker {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.25em;
  color: var(--accent-bright);
}

.brand-name {
  font-size: 1.08rem;
  font-weight: 700;
  color: var(--text);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  color: var(--muted);
  font-size: 0.96rem;
}

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

.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--text);
}

.connect-btn {
  padding: 0.68rem 1rem;
  border-radius: 999px;
  border: 1px solid rgba(125, 211, 252, 0.45);
  background: rgba(56, 189, 248, 0.18);
  color: var(--accent-on-dark);
  font-weight: 600;
}

.connect-btn:hover,
.connect-btn:focus-visible {
  background: rgba(56, 189, 248, 0.28);
  color: #fff;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
  background: var(--panel-strong);
  border-color: var(--line-strong);
  color: var(--accent-bright);
}

.theme-toggle svg {
  display: block;
}

.theme-toggle .icon-moon {
  display: none;
}

:root[data-theme="light"] .theme-toggle .icon-sun {
  display: none;
}

:root[data-theme="light"] .theme-toggle .icon-moon {
  display: block;
}

.site-main {
  position: relative;
  z-index: 1;
}

.hero {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 2rem 3rem;
  padding: 4rem 0 4.5rem;
}

.mission-card-wide {
  grid-column: 1 / -1;
  margin-top: 0.5rem;
}

.eyebrow,
.section-kicker {
  display: inline-flex;
  align-items: center;
  padding: 0.55rem 0.9rem;
  border-radius: 999px;
  border: 1px solid rgba(125, 211, 252, 0.35);
  background: rgba(56, 189, 248, 0.14);
  color: var(--accent-on-dark);
  font-size: 0.73rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.18em;
}

.hero h1 {
  margin: 1rem 0 1.2rem;
  font-size: clamp(2.4rem, 5vw, 5rem);
  line-height: 1.03;
  letter-spacing: -0.03em;
  color: var(--text);
}

.hero p,
.section-head p,
.content-card p,
.project-card p,
.contact-panel p,
.mission-card p {
  color: var(--muted);
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin: 2rem 0 2.25rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.95rem 1.15rem;
  border-radius: 1rem;
  font-weight: 700;
}

.btn-primary {
  background: #f8fafc;
  color: #0f172a;
  box-shadow: 0 14px 40px rgba(255, 255, 255, 0.12);
}

.btn-primary:hover,
.btn-primary:focus-visible {
  background: #fff;
}

.btn-secondary {
  background: var(--panel-strong);
  border: 1px solid var(--line);
  color: var(--text);
}

.btn-secondary:hover,
.btn-secondary:focus-visible {
  background: rgba(255, 255, 255, 0.14);
  border-color: rgba(255, 255, 255, 0.22);
}

.highlights-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
}

.highlight-card,
.content-card,
.project-card,
.news-card {
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: 1.4rem;
  box-shadow: var(--shadow);
}

.highlight-card {
  padding: 1rem;
  color: var(--muted);
  font-size: 0.94rem;
}

.hero-side {
  display: grid;
  gap: 1rem;
}

.portrait-card {
  overflow: hidden;
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.portrait-placeholder {
  position: relative;
  display: flex;
  min-height: 22rem;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  text-align: center;
  padding: 2rem;
  overflow: hidden;
  background: none;
}

.portrait-bg-blur {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: blur(10px);
  transform: scale(1.12);
  z-index: 0;
  pointer-events: none;
}

.portrait-photo-frame {
  position: relative;
  z-index: 1;
  width: 22rem;
  height: 22rem;
  flex-shrink: 0;
  display: block;
  aspect-ratio: 1 / 1;
  margin-bottom: 1rem;
  border-radius: 0;
  overflow: hidden;
  border: 3px solid rgba(255, 255, 255, 0.55);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.55);
}

.portrait-photo {
  width: 100%;
  height: 100%;
  display: block;
  object-fit: cover;
  border-radius: 0;
}

.portrait-name {
  position: relative;
  z-index: 1;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
  text-shadow: 0 1px 6px rgba(0, 0, 0, 0.6);
}

.portrait-note {
  margin-top: 0.4rem;
  color: var(--muted-2);
  font-size: 0.95rem;
}

.card-body {
  padding: 1.4rem 1.5rem 1.6rem;
}

.card-body p {
  margin: 0.9rem 0 0;
  color: var(--muted);
}

.portrait-highlights {
  margin-bottom: 1rem;
}

.portrait-card .highlight-card {
  font-size: 0.88rem;
  padding: 0.85rem;
  line-height: 1.4;
}

.cv-btn-row {
  display: flex;
  gap: 0.75rem;
  margin-top: 1rem;
}

.portrait-card .cv-btn-row {
  margin-top: 0;
}

.cv-btn {
  flex: 1;
  font-size: 0.92rem;
  padding: 0.75rem 1rem;
}

.mission-card {
  border: 1px solid var(--line-strong);
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.2), rgba(99, 102, 241, 0.14));
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.mission-card p {
  color: #e2e8f0;
}

.mission-kicker {
  background: rgba(255, 255, 255, 0.12);
  border-color: rgba(255, 255, 255, 0.2);
  color: var(--accent-on-dark);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.9rem;
  margin-top: 1.35rem;
}

.stats-grid.stats-grid-row {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.stat-card {
  border: 1px solid var(--line);
  background: rgba(10, 17, 31, 0.72);
  border-radius: 1rem;
  padding: 1rem;
}

.stat-value {
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--text);
}

.stat-label {
  margin-top: 0.35rem;
  font-size: 0.78rem;
  color: var(--muted-2);
  line-height: 1.45;
}

.gallery-section {
  padding-bottom: 2rem;
}

.gallery-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1.25rem;
}

.gallery-card {
  overflow: hidden;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--panel);
}

.gallery-card-btn {
  display: block;
  text-decoration: none;
  color: inherit;
  cursor: pointer;
  transition: border-color 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.gallery-card-btn:hover {
  border-color: rgba(96, 165, 250, 0.45);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
  transform: translateY(-2px);
}

.gallery-card-btn:focus-visible {
  outline: 2px solid var(--accent-bright);
  outline-offset: 3px;
}

.gallery-card-btn .gallery-title {
  text-align: center;
}

.gallery-card-disabled {
  cursor: default;
  opacity: 0.55;
  pointer-events: none;
}

.gallery-card-disabled:hover {
  border-color: var(--line);
  box-shadow: none;
  transform: none;
}

.gallery-card-disabled:hover img {
  transform: none;
}

.gallery-image-wrap {
  position: relative;
  height: 16rem;
  overflow: hidden;
}

.gallery-image-wrap img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.gallery-card:hover img {
  transform: scale(1.05);
}

.gallery-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(10, 17, 31, 0.97), rgba(10, 17, 31, 0.35), transparent);
}

.gallery-caption {
  position: absolute;
  left: 1.25rem;
  right: 1.25rem;
  bottom: 1.15rem;
}

.gallery-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text);
}

.gallery-subtitle {
  margin-top: 0.35rem;
  color: #cbd5e1;
  font-size: 0.93rem;
  line-height: 1.45;
}

.section {
  padding: 4.5rem 0;
}

.section-head {
  max-width: 50rem;
  margin-bottom: 2rem;
}

.section-head-tight {
  margin-bottom: 1.5rem;
}

.section-head h2,
.contact-panel h2 {
  margin: 0.9rem 0 0.7rem;
  font-size: clamp(2rem, 3vw, 3.2rem);
  line-height: 1.08;
  letter-spacing: -0.03em;
}

.two-col-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem;
}

.content-card,
.project-card {
  padding: 1.45rem;
  transition: transform 0.2s ease, background 0.2s ease;
}

.content-card h3,
.project-card h3 {
  margin: 0.1rem 0 0.55rem;
  font-size: 1.25rem;
  color: var(--text);
}

.content-card:hover {
  transform: translateY(-4px);
  background: rgba(255, 255, 255, 0.09);
}

.research-subhead {
  margin: 2.75rem 0 1.25rem;
}

.section-head + .research-subhead {
  margin-top: 0;
}

.research-subhead h3 {
  margin: 0;
  font-size: 1.4rem;
  letter-spacing: -0.01em;
  color: var(--text);
}

.research-subhead p {
  margin: 0.4rem 0 0;
  color: var(--muted);
  font-size: 0.98rem;
}

/* Clickable core-direction cards (link to research sub-pages) */
.content-card-link {
  display: flex;
  flex-direction: column;
  cursor: pointer;
}

.content-card-link .card-cta {
  margin-top: auto;
  padding-top: 0.9rem;
  color: var(--accent-bright);
  font-weight: 600;
  font-size: 0.92rem;
}

.content-card-link:hover,
.content-card-link:focus-visible {
  transform: translateY(-4px);
  background: rgba(255, 255, 255, 0.09);
  border-color: rgba(96, 165, 250, 0.45);
}

/* Research topic sub-pages */
.topic-hero {
  padding: 4.5rem 0 1.5rem;
  max-width: 55rem;
}

.topic-hero h1 {
  margin: 0.9rem 0 1rem;
  font-size: clamp(2.2rem, 4.5vw, 3.5rem);
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.topic-hero .lead {
  color: var(--muted);
  font-size: 1.12rem;
  line-height: 1.75;
}

.topic-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  align-items: start;
  margin-bottom: 2.75rem;
}

.ga-figure {
  position: relative;
  margin: 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--line);
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.2), rgba(99, 102, 241, 0.16));
  box-shadow: var(--shadow);
  aspect-ratio: 4 / 3;
}

.ga-figure::after {
  content: "Graphical abstract";
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  text-align: center;
  color: var(--accent-on-dark);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.ga-img {
  position: relative;
  z-index: 1;
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.topic-overview h2 {
  margin: 0 0 0.85rem;
  font-size: 1.5rem;
  letter-spacing: -0.01em;
}

.topic-overview p {
  color: var(--muted);
  margin: 0 0 1rem;
}

.topic-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1.2rem;
}

.topic-tag {
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.05);
  border-radius: 999px;
  padding: 0.35rem 0.8rem;
  font-size: 0.82rem;
  color: var(--muted);
}

.feature-band {
  background: rgba(255, 255, 255, 0.04);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.feature-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 2rem;
}

.feature-note {
  max-width: 20rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.project-card {
  background: rgba(10, 17, 31, 0.75);
}

.project-num {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--muted-2);
  font-weight: 700;
}

.pub-layout {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1.25rem;
}

.card-title {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
}

.paper-list,
.book-list,
.side-stack,
.tag-list {
  display: grid;
  gap: 1rem;
}

.paper-list {
  margin-top: 1.2rem;
}

.paper-group-label {
  margin-top: 1.6rem;
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--accent-bright);
}

.card-title + .paper-group-label {
  margin-top: 1.2rem;
}

.paper-group-label + .paper-list {
  margin-top: 0.7rem;
}

.paper-card {
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: rgba(10, 17, 31, 0.72);
  padding: 1rem;
}

.paper-year {
  color: var(--accent-bright);
  font-size: 0.75rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  font-weight: 800;
}

.paper-title {
  margin-top: 0.5rem;
  font-weight: 700;
  color: var(--text);
}

.paper-authors {
  margin-top: 0.4rem;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.5;
}

.paper-venue {
  margin-top: 0.3rem;
  color: var(--muted-2);
  font-size: 0.92rem;
}

.book-item,
.tag-item {
  border: 1px solid var(--line);
  border-radius: 0.9rem;
  background: rgba(10, 17, 31, 0.72);
  padding: 0.9rem 1rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.people-panel {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.07), rgba(255, 255, 255, 0.04));
  padding: 2rem;
}

.three-col-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
}

.news-card {
  padding: 1.1rem 1rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.contact-section {
  padding-top: 2rem;
  padding-bottom: 6rem;
}

.contact-panel {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 1.25rem;
  align-items: stretch;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: linear-gradient(145deg, rgba(56, 189, 248, 0.16), rgba(99, 102, 241, 0.1));
  padding: 2rem;
}

.contact-main {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.contact-main .contact-card {
  margin-top: 1.25rem;
}

.contact-aside {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  min-height: 100%;
}

.contact-map {
  flex: 1 1 auto;
  min-height: 12rem;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: rgba(10, 17, 31, 0.88);
}

.contact-map iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}

.contact-map-link {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-bright);
  text-decoration: none;
  flex-shrink: 0;
}

.contact-map-link:hover,
.contact-map-link:focus-visible {
  color: var(--text);
}

.contact-panel p {
  color: #e2e8f0;
}

.contact-kicker {
  background: rgba(255, 255, 255, 0.12);
  border-color: rgba(255, 255, 255, 0.22);
  color: var(--accent-on-dark);
}

.contact-card {
  border: 1px solid var(--line);
  border-radius: 1.25rem;
  background: rgba(10, 17, 31, 0.88);
  padding: 1.25rem;
  color: var(--muted);
}

.contact-card div + div {
  margin-top: 0.35rem;
}

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

.brand-link {
  text-decoration: none;
  color: inherit;
}

.nav-links .nav-current {
  color: var(--text);
  font-weight: 700;
}

.courses-hero {
  padding: 4.5rem 0 2rem;
  max-width: 50rem;
}

.courses-hero h1 {
  margin: 0.9rem 0 1rem;
  font-size: clamp(2.2rem, 4.5vw, 3.5rem);
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.courses-hero p {
  margin: 0 0 1rem;
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.7;
}

.courses-hero p:last-child {
  margin-bottom: 0;
}

.course-back-link {
  display: inline-block;
  margin-bottom: 1.25rem;
  color: var(--accent-bright);
  font-size: 0.92rem;
  font-weight: 600;
  transition: color 0.2s ease;
}

.course-back-link:hover,
.course-back-link:focus-visible {
  color: var(--text);
}

.courses-index-section {
  padding-top: 0;
  max-width: 50rem;
}

.courses-index-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
}

.course-index-card {
  display: block;
  overflow: hidden;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--panel);
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.course-index-card:hover,
.course-index-card:focus-visible {
  border-color: rgba(96, 165, 250, 0.45);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
  transform: translateY(-2px);
}

.course-index-media {
  position: relative;
  height: 18rem;
  overflow: hidden;
}

.course-index-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.course-index-card:hover img {
  transform: scale(1.05);
}

.course-index-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(10, 17, 31, 0.97), rgba(10, 17, 31, 0.4), transparent);
}

.course-index-caption {
  position: absolute;
  left: 1.25rem;
  right: 1.25rem;
  bottom: 1.15rem;
}

.course-index-caption .course-code {
  margin-bottom: 0.5rem;
}

.course-index-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.25;
}

.course-index-subtitle {
  margin-top: 0.4rem;
  color: #cbd5e1;
  font-size: 0.93rem;
  line-height: 1.45;
}

.course-card {
  display: grid;
  grid-template-columns: minmax(12rem, 16rem) 1fr;
  gap: 2rem;
  align-items: start;
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: var(--radius);
  padding: 1.75rem;
  box-shadow: var(--shadow);
}

.course-card-media {
  border-radius: 1.25rem;
  overflow: hidden;
  border: 1px solid var(--line);
  aspect-ratio: 1 / 1;
}

.course-card-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.course-card-body h2 {
  margin: 0 0 1rem;
  font-size: clamp(1.35rem, 2.5vw, 1.75rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.course-card-body p {
  margin: 0 0 1rem;
  color: var(--muted);
  line-height: 1.65;
}

.course-card-body p:last-child {
  margin-bottom: 0;
}

.course-code {
  display: inline-flex;
  margin-bottom: 0.75rem;
  padding: 0.4rem 0.75rem;
  border-radius: 999px;
  border: 1px solid rgba(125, 211, 252, 0.35);
  background: rgba(56, 189, 248, 0.12);
  color: var(--accent-on-dark);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.course-prereq {
  margin-top: 0.25rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  font-size: 0.95rem;
}

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

.course-materials {
  margin-top: 0;
}

.course-materials-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
}

.course-material-link {
  display: block;
  padding: 0.85rem 1rem;
  border: 1px solid var(--line);
  background: rgba(10, 17, 31, 0.72);
  border-radius: 1rem;
  color: var(--muted);
  font-size: 0.94rem;
  font-weight: 500;
  transition: border-color 0.2s ease, background 0.2s ease, color 0.2s ease, transform 0.2s ease;
}

.course-material-link:hover,
.course-material-link:focus-visible {
  border-color: rgba(125, 211, 252, 0.45);
  background: rgba(56, 189, 248, 0.12);
  color: var(--text);
  transform: translateY(-1px);
}

@media (max-width: 1080px) {
  .hero,
  .pub-layout,
  .contact-panel {
    grid-template-columns: 1fr;
  }

  .contact-map {
    flex: none;
    height: 14rem;
    min-height: 14rem;
  }

  .gallery-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .two-col-grid,
  .three-col-grid,
  .topic-layout {
    grid-template-columns: 1fr;
  }

  .feature-head {
    flex-direction: column;
    align-items: flex-start;
  }

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

  .course-card-media {
    max-width: 16rem;
  }
}

@media (max-width: 820px) {
  .nav-links {
    display: none;
  }

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

  .container {
    width: min(var(--max), calc(100% - 1.5rem));
  }

  .hero {
    padding-top: 2.5rem;
  }

  .course-materials-grid {
    grid-template-columns: 1fr;
  }
}

/* ===================== LIGHT THEME ===================== */
/* Blue/purple, light — same vibe as the dark default. Activated by
   data-theme="light" on <html> (set by theme.js / the navbar toggle). */
:root[data-theme="light"] {
  --bg: #e4ecfa;
  --bg-elevated: #eef4ff;
  --panel: rgba(255, 255, 255, 0.72);
  --panel-strong: rgba(255, 255, 255, 0.9);
  --line: rgba(39, 46, 104, 0.14);
  --line-strong: rgba(37, 99, 235, 0.45);
  --text: #1b2140;
  --muted: #4a5578;
  --muted-2: #616c92;
  --accent: #1d4ed8;
  --accent-bright: #1e40af;
  --accent-on-dark: #1e3a8a;
  --shadow: 0 18px 45px rgba(48, 55, 120, 0.14);
}

/* Ambient background glows — richer blue/purple */
:root[data-theme="light"] .glow-1 { background: rgba(37, 99, 235, 0.32); }
:root[data-theme="light"] .glow-2 { background: rgba(29, 78, 216, 0.3); }
:root[data-theme="light"] .glow-3 { background: rgba(37, 99, 235, 0.24); }

/* Frosted header */
:root[data-theme="light"] .site-header {
  background: rgba(246, 248, 255, 0.85);
}

/* Pills / kickers */
:root[data-theme="light"] .eyebrow,
:root[data-theme="light"] .section-kicker,
:root[data-theme="light"] .course-code {
  border-color: rgba(37, 99, 235, 0.45);
  background: rgba(37, 99, 235, 0.16);
}

:root[data-theme="light"] .connect-btn {
  border-color: rgba(37, 99, 235, 0.5);
  background: rgba(37, 99, 235, 0.2);
}

:root[data-theme="light"] .connect-btn:hover,
:root[data-theme="light"] .connect-btn:focus-visible {
  background: #1d4ed8;
  color: #fff;
}

:root[data-theme="light"] .mission-kicker,
:root[data-theme="light"] .contact-kicker {
  background: rgba(37, 99, 235, 0.18);
  border-color: rgba(37, 99, 235, 0.38);
}

/* Buttons */
:root[data-theme="light"] .btn-primary {
  background: #1d4ed8;
  color: #fff;
  box-shadow: 0 14px 34px rgba(37, 99, 235, 0.32);
}

:root[data-theme="light"] .btn-primary:hover,
:root[data-theme="light"] .btn-primary:focus-visible {
  background: #1e40af;
}

:root[data-theme="light"] .btn-secondary:hover,
:root[data-theme="light"] .btn-secondary:focus-visible {
  background: rgba(37, 99, 235, 0.1);
  border-color: rgba(37, 99, 235, 0.3);
}

/* Solid dark cards → light cards */
:root[data-theme="light"] .stat-card,
:root[data-theme="light"] .paper-card,
:root[data-theme="light"] .book-item,
:root[data-theme="light"] .tag-item,
:root[data-theme="light"] .course-material-link,
:root[data-theme="light"] .contact-map,
:root[data-theme="light"] .contact-card {
  background: rgba(255, 255, 255, 0.75);
}

:root[data-theme="light"] .project-card {
  background: rgba(255, 255, 255, 0.7);
}

/* Hover surfaces */
:root[data-theme="light"] .content-card:hover,
:root[data-theme="light"] .content-card-link:hover,
:root[data-theme="light"] .content-card-link:focus-visible {
  background: rgba(255, 255, 255, 0.95);
}

:root[data-theme="light"] .content-card-link:hover,
:root[data-theme="light"] .content-card-link:focus-visible,
:root[data-theme="light"] .gallery-card-btn:hover,
:root[data-theme="light"] .course-index-card:hover,
:root[data-theme="light"] .course-index-card:focus-visible {
  border-color: rgba(37, 99, 235, 0.4);
}

/* Subtle tinted surfaces */
:root[data-theme="light"] .topic-tag { background: rgba(37, 99, 235, 0.12); }
:root[data-theme="light"] .feature-band { background: rgba(37, 99, 235, 0.09); }

/* Gradient panels */
:root[data-theme="light"] .mission-card,
:root[data-theme="light"] .ga-figure {
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.28), rgba(29, 78, 216, 0.3));
}

:root[data-theme="light"] .contact-panel {
  background: linear-gradient(145deg, rgba(37, 99, 235, 0.24), rgba(29, 78, 216, 0.24));
}

:root[data-theme="light"] .people-panel {
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.85), rgba(255, 255, 255, 0.6));
}

/* Copy sitting on the gradient panels → dark ink in light theme */
:root[data-theme="light"] .mission-card p,
:root[data-theme="light"] .contact-panel p {
  color: var(--text);
}

/* Course material link hover */
:root[data-theme="light"] .course-material-link:hover,
:root[data-theme="light"] .course-material-link:focus-visible {
  border-color: rgba(37, 99, 235, 0.4);
  background: rgba(37, 99, 235, 0.1);
}

/* Portrait frame */
:root[data-theme="light"] .portrait-photo-frame {
  border-color: rgba(39, 46, 104, 0.18);
}

/* Text sitting over images — keep it light in both themes */
:root[data-theme="light"] .gallery-title,
:root[data-theme="light"] .course-index-title,
:root[data-theme="light"] .portrait-name {
  color: #f8fafc;
}

/* ===================== MOBILE NAV / DRAWER + AUTO-HIDE HEADER ===================== */
/* Auto-hide the sticky header on scroll-down (toggled by theme.js). */
.site-header {
  transition: transform 0.3s ease;
  will-change: transform;
}
.site-header.site-header--hidden {
  transform: translateY(-100%);
}

/* Hamburger button — only shown on small screens */
.nav-toggle {
  display: none;
  width: 2.6rem;
  height: 2.6rem;
  padding: 0;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--panel);
  cursor: pointer;
  position: relative;
}
.nav-toggle span {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 1.1rem;
  height: 2px;
  border-radius: 2px;
  background: var(--text);
  transition: transform 0.25s ease, opacity 0.2s ease;
}
.nav-toggle span:nth-child(1) { transform: translate(-50%, -50%) translateY(-0.32rem); }
.nav-toggle span:nth-child(2) { transform: translate(-50%, -50%); }
.nav-toggle span:nth-child(3) { transform: translate(-50%, -50%) translateY(0.32rem); }
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translate(-50%, -50%) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translate(-50%, -50%) rotate(-45deg); }

/* Slide-in drawer */
.mobile-menu {
  position: fixed;
  inset: 0;
  z-index: 60;
  visibility: hidden;
}
.mobile-menu.open { visibility: visible; }
.mobile-menu-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(2, 6, 23, 0.55);
  opacity: 0;
  transition: opacity 0.3s ease;
}
.mobile-menu.open .mobile-menu-backdrop { opacity: 1; }
.mobile-menu-panel {
  position: absolute;
  top: 0;
  right: 0;
  height: 100%;
  width: min(82vw, 20rem);
  background: var(--bg-elevated);
  border-left: 1px solid var(--line);
  box-shadow: -24px 0 60px rgba(0, 0, 0, 0.4);
  padding: 5.5rem 1.5rem 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  overflow-y: auto;
  transform: translateX(100%);
  transition: transform 0.3s ease;
}
.mobile-menu.open .mobile-menu-panel { transform: translateX(0); }
.mobile-menu-panel a {
  padding: 0.95rem 0.4rem;
  color: var(--muted);
  font-size: 1.08rem;
  font-weight: 600;
  border-bottom: 1px solid var(--line);
}
.mobile-menu-panel a:hover,
.mobile-menu-panel a:focus-visible,
.mobile-menu-panel a.nav-current { color: var(--text); }
.mobile-menu-panel .mobile-connect {
  margin-top: 1.25rem;
  padding: 0.85rem 1rem;
  text-align: center;
  border-bottom: none;
  color: var(--accent-on-dark);
}

@media (max-width: 820px) {
  .nav-actions .connect-btn { display: none; }
  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }
}

/* Respect reduced-motion preferences */
@media (prefers-reduced-motion: reduce) {
  .site-header,
  .mobile-menu-panel,
  .mobile-menu-backdrop,
  .nav-toggle span { transition: none; }
}

/* ===================== PHONE / RESPONSIVE REFINEMENTS ===================== */
@media (max-width: 820px) {
  /* Tighter gap between the sticky navbar and the first block of each page */
  .hero { padding-top: 1.75rem; }
  .courses-hero,
  .topic-hero { padding-top: 1.75rem; }
  .site-main > .section:first-child { padding-top: 1.75rem; }

  /* Research Mission stat tiles: 4-across is too thin on small screens */
  .stats-grid.stats-grid-row { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 560px) {
  /* Keep the hero call-to-action buttons side by side instead of stacking */
  .cta-row { flex-wrap: nowrap; }
  .cta-row .btn {
    flex: 1 1 0;
    padding-left: 0.6rem;
    padding-right: 0.6rem;
    font-size: 0.95rem;
  }

  /* Stat tiles fully stacked (vertical) on phones */
  .stats-grid.stats-grid-row { grid-template-columns: 1fr; }
}