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

:root {
  --color-bg: #ffffff;
  --color-text: #1a1a2e;
  --color-text-muted: #555;
  --color-accent: #2563eb;
  --color-accent-light: #dbeafe;
  --color-dark: #1a1a2e;
  --color-dark-soft: #2d2d44;
  --color-surface: #f8f9fb;
  --color-border: #e2e5ea;
  --color-card: #ffffff;
  --color-shadow: rgba(0,0,0,0.06);
  --color-nav-bg: rgba(26, 26, 46, 0.95);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-serif: 'Source Serif 4', Georgia, serif;
  --container: 1100px;
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 6rem;
}

html { scroll-behavior: smooth; scroll-padding-top: 5rem; }

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--color-text);
  background: var(--color-bg);
}

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

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

h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  line-height: 1.25;
}

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

/* === Navigation === */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: var(--color-nav-bg);
  backdrop-filter: blur(8px);
  transition: box-shadow 0.3s;
}

.site-nav.scrolled {
  box-shadow: 0 1px 8px rgba(0,0,0,0.15);
}

.nav-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--space-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4rem;
}

.nav-brand {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 1.15rem;
  color: #fff;
  text-decoration: none;
  letter-spacing: 0.02em;
}

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

.nav-links a {
  color: rgba(255,255,255,0.8);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover { color: #fff; text-decoration: none; }

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

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: #fff;
  border-radius: 1px;
}

@media (max-width: 768px) {
  .nav-toggle { display: flex; }
  .nav-links {
    display: none;
    position: absolute;
    top: 4rem;
    left: 0;
    right: 0;
    background: var(--color-dark);
    flex-direction: column;
    padding: var(--space-sm) var(--space-md);
    gap: 0;
  }
  .nav-links.open { display: flex; }
  .nav-links li { padding: var(--space-xs) 0; }
}

/* === Hero === */
.hero {
  position: relative;
  padding: 10rem 0 6rem;
  background: linear-gradient(135deg, var(--color-dark) 0%, var(--color-dark-soft) 100%);
  color: #fff;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0.15;
  z-index: 0;
}

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

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.25rem);
  margin-bottom: var(--space-sm);
  color: #fff;
}

.hero .tagline {
  font-size: 1.2rem;
  color: rgba(255,255,255,0.75);
  max-width: 600px;
  margin-bottom: var(--space-lg);
}

/* Pathway cards */
.pathways {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-sm);
  margin-top: var(--space-md);
}

.pathway-card {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: 8px;
  padding: var(--space-sm) var(--space-md);
  color: #fff;
  text-decoration: none;
  transition: background 0.2s, transform 0.2s;
}

.pathway-card:hover {
  background: rgba(255,255,255,0.14);
  transform: translateY(-2px);
  text-decoration: none;
  color: #fff;
}

.pathway-card .card-label {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: rgba(255,255,255,0.5);
  margin-bottom: 0.25rem;
}

.pathway-card .card-title {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 1rem;
}

.pathway-card .card-arrow {
  display: inline-block;
  margin-left: 0.25rem;
  transition: transform 0.2s;
}

.pathway-card:hover .card-arrow { transform: translateX(3px); }

/* === Sections === */
.section {
  padding: var(--space-xl) 0;
}

.section-alt {
  background: var(--color-surface);
}

.section-header {
  margin-bottom: var(--space-lg);
}

.section-header h2 {
  font-size: clamp(1.75rem, 3vw, 2.25rem);
  margin-bottom: var(--space-xs);
}

.section-header p {
  color: var(--color-text-muted);
  max-width: 650px;
  font-size: 1.05rem;
}

/* === Research Areas === */
.research-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--space-md);
}

@media (min-width: 900px) {
  .research-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.research-card {
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: var(--space-md);
  background: var(--color-card);
  transition: box-shadow 0.2s;
}

.research-card:hover {
  box-shadow: 0 4px 16px var(--color-shadow);
}

.research-card h3 {
  font-size: 1.15rem;
  margin-bottom: var(--space-xs);
}

.research-card p {
  color: var(--color-text-muted);
  font-size: 0.92rem;
  margin-bottom: var(--space-sm);
}

.research-card .topics {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.research-card .card-people {
  margin-top: var(--space-sm);
  padding-top: var(--space-sm);
  border-top: 1px solid var(--color-border);
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.8;
}

.research-card .card-people a {
  color: var(--color-text);
  font-weight: 500;
}

.research-card .card-people a:hover {
  color: var(--color-accent);
}

.tag {
  display: inline-block;
  background: var(--color-accent-light);
  color: var(--color-accent);
  font-size: 0.78rem;
  font-weight: 500;
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
}

/* === Projects === */
.projects-list {
  display: grid;
  gap: var(--space-sm);
  margin-top: var(--space-md);
}

.project-item {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: var(--space-sm);
  align-items: baseline;
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--color-border);
}

.project-item h4 {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
}

.project-item .project-meta {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}

.project-item p {
  grid-column: 1 / -1;
  font-size: 0.92rem;
  color: var(--color-text-muted);
}

/* === People === */
.people-section-title {
  font-size: 1.1rem;
  font-family: var(--font-sans);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
  margin-top: var(--space-lg);
  padding-bottom: var(--space-xs);
  border-bottom: 2px solid var(--color-border);
}

.people-section-title:first-of-type {
  margin-top: 0;
}

.people-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--space-md);
}

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

.person-card img {
  width: 140px;
  height: 140px;
  border-radius: 12px;
  object-fit: cover;
  margin: 0 auto var(--space-sm);
  filter: grayscale(20%);
  transition: filter 0.3s;
}

.person-card:hover img {
  filter: grayscale(0%);
}

.person-card h4 {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.15rem;
}

.person-card h4 a {
  color: var(--color-text);
}

.person-card h4 a:hover {
  color: var(--color-accent);
}

.person-card .role {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-bottom: 0.25rem;
}

.person-card .interests {
  font-size: 0.8rem;
  color: var(--color-accent);
  font-style: italic;
}

.person-card .card-areas {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  margin-top: 0.35rem;
}

.person-card .card-areas a {
  color: var(--color-text-muted);
}

.person-card .card-areas a:hover {
  color: var(--color-accent);
}

/* Alumni */
.alumni-list {
  columns: 2;
  column-gap: var(--space-lg);
  font-size: 0.92rem;
  color: var(--color-text-muted);
}

.alumni-list p {
  margin-bottom: var(--space-xs);
  break-inside: avoid;
}

@media (max-width: 600px) {
  .alumni-list { columns: 1; }
}

/* === News === */
.news-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
}

@media (max-width: 768px) {
  .news-grid { grid-template-columns: 1fr; }
}

.news-column h3 {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
  padding-bottom: var(--space-xs);
  border-bottom: 2px solid var(--color-border);
}

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

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

.news-date {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.news-item p {
  font-size: 0.92rem;
  margin-top: 0.25rem;
  color: var(--color-text-muted);
}

/* Talks table */
.talks-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.talks-table th {
  text-align: left;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  padding: var(--space-xs) var(--space-sm) var(--space-xs) 0;
  border-bottom: 2px solid var(--color-border);
}

.talks-table td {
  padding: var(--space-xs) var(--space-sm) var(--space-xs) 0;
  border-bottom: 1px solid var(--color-border);
  vertical-align: top;
}

.talks-table tr.past { color: var(--color-text-muted); }

/* === About === */
.pillars {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-md);
  margin-top: var(--space-lg);
}

.pillar {
  text-align: center;
  padding: var(--space-md);
}

.pillar-icon {
  font-size: 2rem;
  margin-bottom: var(--space-sm);
}

.pillar h3 {
  font-size: 1.1rem;
  margin-bottom: var(--space-xs);
}

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

/* Mission/Vision */
.statement-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  margin-top: var(--space-md);
}

.statement h3 {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-accent);
  margin-bottom: var(--space-xs);
}

.statement p {
  color: var(--color-text-muted);
  font-size: 1rem;
}

@media (max-width: 600px) {
  .statement-grid { grid-template-columns: 1fr; }
}

/* === Contact === */
.contact-section {
  background: var(--color-dark);
  color: #fff;
  padding: var(--space-xl) 0;
}

.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--space-lg);
}

.contact-block h3 {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: rgba(255,255,255,0.5);
  margin-bottom: var(--space-sm);
}

.contact-block h4 {
  font-family: var(--font-sans);
  font-size: 1.1rem;
  font-weight: 600;
  color: #fff;
  margin-bottom: 0.15rem;
}

.contact-block .contact-role {
  font-size: 0.88rem;
  color: rgba(255,255,255,0.6);
  margin-bottom: var(--space-sm);
}

.contact-block a {
  color: rgba(255,255,255,0.8);
}

.contact-block a:hover { color: #fff; }

.contact-block .contact-detail {
  font-size: 0.92rem;
  margin-bottom: 0.35rem;
  color: rgba(255,255,255,0.75);
}

/* Courses (small subsection) */
.courses-list {
  columns: 2;
  column-gap: var(--space-lg);
  list-style: none;
}

.courses-list li {
  padding: 0.35rem 0;
  font-size: 0.92rem;
  break-inside: avoid;
}

@media (max-width: 600px) {
  .courses-list { columns: 1; }
}

/* === Footer === */
.site-footer {
  padding: var(--space-md) 0;
  background: var(--color-surface);
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.site-footer a { color: var(--color-text-muted); }
.site-footer a:hover { color: var(--color-text); }

/* === Utilities === */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
}

/* === Dark mode (auto, follows OS preference) === */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0d1017;
    --color-text: #e6e8ee;
    --color-text-muted: #9aa3b2;
    --color-accent: #7cb0fb;
    --color-accent-light: rgba(124, 176, 251, 0.16);
    --color-dark: #060810;
    --color-dark-soft: #131724;
    --color-surface: #161b25;
    --color-border: #252a36;
    --color-card: #1a1f2c;
    --color-shadow: rgba(0,0,0,0.4);
    --color-nav-bg: rgba(6, 8, 16, 0.85);
  }

  .person-card img { filter: grayscale(15%) brightness(0.95); }
  .person-card:hover img { filter: grayscale(0%) brightness(1); }

  img { color-scheme: dark; }
}