/* ────────────────────────────────────────────────────────
   Variables
──────────────────────────────────────────────────────── */
:root {
  --bg:           #f8f9fa;
  --bg-alt:       #eef1f6;
  --text:         #1a1a2e;
  --text-muted:   #5a6a85;
  --accent:       #4a6fa5;
  --accent-dark:  #3a5f95;
  --accent-light: #d4e3f5;
  --border:       #dde2ec;
  --white:        #ffffff;
  --radius:       8px;
  --shadow:       0 2px 12px rgba(74, 111, 165, 0.10);
  --shadow-hover: 0 8px 28px rgba(74, 111, 165, 0.18);
  --nav-height:   64px;
  --ease:         0.2s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

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

a:hover { color: var(--accent-dark); }

/* ────────────────────────────────────────────────────────
   Navigation
──────────────────────────────────────────────────────── */
#navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--nav-height);
  background: rgba(248, 249, 250, 0.92);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  transition: box-shadow var(--ease);
}

#navbar.scrolled {
  box-shadow: 0 2px 20px rgba(26, 26, 46, 0.08);
}

.nav-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 28px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.nav-brand {
  font-size: 0.97rem;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  letter-spacing: -0.01em;
}

.nav-brand:hover { color: var(--accent); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 2px;
  list-style: none;
}

.nav-links a {
  display: block;
  padding: 6px 12px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  border-radius: 6px;
  transition: color var(--ease), background var(--ease);
}

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

/* Hamburger */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
  border-radius: 6px;
  transition: background var(--ease);
}

.nav-toggle:hover { background: var(--accent-light); }

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

/* Hamburger → X when open */
.nav-toggle[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.nav-toggle[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ────────────────────────────────────────────────────────
   Shared section layout
──────────────────────────────────────────────────────── */
.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 88px 28px;
}

.alt-bg { background: var(--bg-alt); }

.section-label {
  display: block;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

section h2 {
  font-size: 1.75rem;
  font-weight: 600;
  letter-spacing: -0.025em;
  color: var(--text);
  line-height: 1.2;
}

section h2::after {
  content: '';
  display: block;
  width: 36px;
  height: 3px;
  background: var(--accent);
  margin-top: 12px;
  border-radius: 2px;
}

.section-intro {
  color: var(--text-muted);
  margin-top: 18px;
  margin-bottom: 40px;
  font-size: 0.95rem;
}

/* ────────────────────────────────────────────────────────
   Hero
──────────────────────────────────────────────────────── */
#hero {
  background: var(--bg-alt);
  padding-top: var(--nav-height);
  min-height: 100vh;
  display: flex;
  align-items: center;
}

.hero-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 80px 28px;
  display: flex;
  align-items: center;
  gap: 72px;
}

.hero-text { flex: 1; min-width: 0; }

.hero-text h1 {
  font-size: clamp(2.1rem, 5vw, 3.1rem);
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.035em;
  color: var(--text);
  margin-bottom: 14px;
}

.hero-title {
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--text-muted);
  letter-spacing: 0.01em;
  margin-bottom: 22px;
}

.hero-tagline {
  font-size: 1.05rem;
  color: var(--text);
  line-height: 1.75;
  margin-bottom: 32px;
  max-width: 460px;
}

.social-links {
  display: flex;
  gap: 10px;
  margin-bottom: 32px;
}

.social-links a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--white);
  border: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.95rem;
  transition: color var(--ease), border-color var(--ease),
              background var(--ease), transform var(--ease);
}

.social-links a:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-light);
  transform: translateY(-3px);
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 26px;
  background: var(--accent);
  color: var(--white) !important;
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: var(--radius);
  letter-spacing: 0.01em;
  transition: background var(--ease), transform var(--ease), box-shadow var(--ease);
}

.btn-primary:hover {
  background: var(--accent-dark);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(74, 111, 165, 0.32);
}

.hero-photo { flex-shrink: 0; }

.hero-photo img {
  width: 230px;
  height: 230px;
  border-radius: 50%;
  object-fit: cover;
  border: 5px solid var(--white);
  box-shadow: var(--shadow);
}

/* ────────────────────────────────────────────────────────
   About
──────────────────────────────────────────────────────── */
.about-text {
  margin-top: 28px;
  max-width: 680px;
}

.about-text p {
  margin-bottom: 16px;
  color: var(--text);
}

.about-text p:last-child { margin-bottom: 0; }

/* ────────────────────────────────────────────────────────
   Timeline (shared by Education & Experience)
──────────────────────────────────────────────────────── */
.timeline {
  position: relative;
  margin-top: 40px;
}

/* Vertical line */
.timeline::before {
  content: '';
  position: absolute;
  left: 138px;
  top: 6px;
  bottom: 6px;
  width: 1px;
  background: var(--border);
}

.timeline-item {
  display: grid;
  grid-template-columns: 138px 1fr;
  margin-bottom: 36px;
}

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

.timeline-date {
  padding-right: 22px;
  text-align: right;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-muted);
  padding-top: 3px;
  line-height: 1.4;
}

.timeline-content {
  padding-left: 26px;
  position: relative;
}

/* Dot on the timeline line */
.timeline-content::before {
  content: '';
  position: absolute;
  left: -5px;
  top: 5px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg-alt); /* default: alt-bg sections */
}

/* Override dot border to match each section's background */
#education .timeline-content::before {
  border-color: var(--bg-alt);
}

#experience .timeline-content::before {
  border-color: var(--bg);
}

.timeline-content h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 5px;
  line-height: 1.35;
}

.timeline-place {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.5;
}

.timeline-place a {
  color: var(--text-muted);
}

.timeline-place a:hover {
  color: var(--accent);
}

/* ────────────────────────────────────────────────────────
   Research grid
──────────────────────────────────────────────────────── */
.research-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
}

.research-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  transition: box-shadow var(--ease), border-color var(--ease), transform var(--ease);
}

.research-card:hover {
  box-shadow: var(--shadow-hover);
  border-color: var(--accent-light);
  transform: translateY(-4px);
}

.card-header {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
}

.badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 20px;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  white-space: nowrap;
}

.badge-published { background: #d1fae5; color: #065f46; }
.badge-review    { background: #fef3c7; color: #92400e; }
.badge-prep      { background: #f1f5f9; color: #475569; }

.card-journal {
  font-size: 0.77rem;
  color: var(--text-muted);
  font-style: italic;
}

.research-card h3 {
  font-size: 0.97rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.45;
}

.research-card p {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.65;
  flex: 1;
}

.card-links {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 6px;
}

.card-link {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--accent);
  padding: 4px 11px;
  border: 1px solid var(--accent-light);
  border-radius: 5px;
  transition: background var(--ease), border-color var(--ease), color var(--ease);
}

.card-link:hover {
  background: var(--accent-light);
  border-color: var(--accent);
  color: var(--accent-dark);
}

/* ────────────────────────────────────────────────────────
   Contact
──────────────────────────────────────────────────────── */
.contact-intro {
  color: var(--text-muted);
  margin-top: 18px;
  margin-bottom: 36px;
  max-width: 480px;
}

.contact-list {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.contact-item {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  color: var(--text);
  font-size: 0.97rem;
  transition: color var(--ease);
  width: fit-content;
}

.contact-item i {
  width: 20px;
  text-align: center;
  color: var(--accent);
  font-size: 1rem;
  flex-shrink: 0;
}

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

/* ────────────────────────────────────────────────────────
   Footer
──────────────────────────────────────────────────────── */
footer {
  background: var(--text);
  padding: 32px 28px;
  text-align: center;
}

footer p {
  font-size: 0.83rem;
  color: #8899bb;
}

/* ────────────────────────────────────────────────────────
   Responsive
──────────────────────────────────────────────────────── */
@media (max-width: 720px) {
  /* Mobile nav */
  .nav-toggle { display: flex; }

  .nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 12px 20px 16px;
    gap: 2px;
    box-shadow: 0 8px 24px rgba(26, 26, 46, 0.10);
  }

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

  .nav-links a {
    padding: 10px 12px;
    font-size: 0.95rem;
    border-radius: 6px;
  }

  /* Hero stacked */
  #hero { min-height: auto; }

  .hero-inner {
    flex-direction: column-reverse;
    text-align: center;
    padding: 64px 24px 56px;
    gap: 32px;
  }

  .hero-tagline { max-width: 100%; }

  .social-links { justify-content: center; }

  .hero-photo img {
    width: 160px;
    height: 160px;
  }

  /* Timeline: single column */
  .timeline::before { display: none; }

  .timeline-item {
    grid-template-columns: 1fr;
    padding-left: 22px;
    border-left: 1px solid var(--border);
    position: relative;
    margin-bottom: 32px;
    padding-bottom: 4px;
  }

  .timeline-item::before {
    content: '';
    position: absolute;
    left: -5px;
    top: 4px;
    width: 9px;
    height: 9px;
    border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--bg-alt);
  }

  #education .timeline-item::before {
    border-color: var(--bg-alt);
  }

  #experience .timeline-item::before {
    border-color: var(--bg);
  }

  /* Hide the ::before dot from timeline-content on mobile since item has it now */
  .timeline-content::before { display: none; }

  .timeline-date {
    text-align: left;
    padding-right: 0;
    margin-bottom: 4px;
    order: -1;
  }

  .timeline-content { padding-left: 0; }

  /* Research single col */
  .research-grid { grid-template-columns: 1fr; }

  .container { padding: 64px 20px; }
}

@media (max-width: 480px) {
  .hero-text h1 { font-size: 2rem; }
  section h2 { font-size: 1.5rem; }
}

/* ────────────────────────────────────────────────────────
   News / Press
──────────────────────────────────────────────────────── */
.news-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 32px;
}

.news-item {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 14px 18px;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  text-decoration: none;
  transition: border-color var(--ease), box-shadow var(--ease), transform var(--ease);
}

.news-item:hover {
  border-color: var(--accent-light);
  box-shadow: var(--shadow);
  transform: translateX(4px);
  color: var(--text);
}

.news-source {
  flex-shrink: 0;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  min-width: 130px;
}

.news-headline {
  font-size: 0.9rem;
  color: var(--text);
  flex: 1;
  line-height: 1.45;
}

.news-icon {
  flex-shrink: 0;
  font-size: 0.72rem;
  color: var(--text-muted);
  margin-left: auto;
  padding-left: 8px;
}

@media (max-width: 560px) {
  .news-item { flex-wrap: wrap; gap: 6px; }
  .news-source { min-width: auto; }
  .news-icon { display: none; }
}

/* ────────────────────────────────────────────────────────
   Publications (live from Semantic Scholar)
──────────────────────────────────────────────────────── */
.pub-loading {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--text-muted);
  font-size: 0.9rem;
  padding: 24px 0;
}

.pub-spinner {
  display: inline-block;
  width: 18px;
  height: 18px;
  border: 2px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  flex-shrink: 0;
}

@keyframes spin { to { transform: rotate(360deg); } }

.pub-list-inner {
  display: flex;
  flex-direction: column;
  gap: 16px;
  margin-top: 8px;
}

.pub-item {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: box-shadow var(--ease), border-color var(--ease), transform var(--ease);
}

.pub-item:hover {
  box-shadow: var(--shadow);
  border-color: var(--accent-light);
  transform: translateY(-2px);
}

.pub-citation {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.01em;
}

.pub-title {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text);
  line-height: 1.5;
  transition: color var(--ease);
}

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

.pub-venue {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-style: italic;
  font-weight: 400;
}

.pub-fallback {
  color: var(--text-muted);
  font-size: 0.9rem;
  padding: 16px 0;
}

.pub-fallback a { color: var(--accent); }