:root {
  --bg: #fafafa;
  --text: #1a1a1a;
  --muted: #6b7280;
  --accent: #2563eb;
  --border: #e5e7eb;
  --max-w: 800px;
  --header-h: 88px;
}

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

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 1rem;
}

/* ── Skip link ── */

.skip-link {
  position: absolute;
  top: -100%;
  left: 1rem;
  background: var(--text);
  color: var(--bg);
  padding: 0.5rem 1rem;
  border-radius: 4px;
  z-index: 200;
  font-size: 0.875rem;
  text-decoration: none;
}

.skip-link:focus {
  top: 0.75rem;
}

/* ── Header ── */

header {
  position: sticky;
  top: 0;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  padding: 0.6rem 1.5rem;
}

nav {
  max-width: var(--max-w);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.nav-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-name {
  font-weight: 600;
  font-size: 0.95rem;
  letter-spacing: -0.01em;
  white-space: nowrap;
}

.nav-links {
  display: flex;
  gap: 1.25rem;
  align-items: center;
  flex-wrap: nowrap;
  overflow-x: auto;
  scrollbar-width: none;
  -ms-overflow-style: none;
  padding-bottom: 2px;
}

.nav-links::-webkit-scrollbar {
  display: none;
}

.nav-links a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.8rem;
  white-space: nowrap;
  transition: color 0.15s;
}

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

/* ── CTA — no !important; specificity via compound selector ── */

a.cta,
.nav-links a.cta,
.hero-links a.cta,
.research-note a.cta,
footer a.cta {
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
}

a.cta:hover,
.nav-links a.cta:hover,
.hero-links a.cta:hover,
.research-note a.cta:hover,
footer a.cta:hover {
  text-decoration: underline;
}

/* ── Hero avatar ── */

.hero-avatar {
  width: 240px;
  height: 240px;
  border-radius: 50%;
  object-fit: cover;
  display: block;
  margin: 0 auto 1.5rem;
}

/* ── Hero ── */

#hero {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 6rem 1.5rem 5rem;
}

#hero h1 {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 0.5rem;
}

.tagline {
  font-size: 1rem;
  color: var(--muted);
  margin-bottom: 1.75rem;
}

.positioning {
  font-size: 1.05rem;
  line-height: 1.75;
  max-width: 600px;
  margin-bottom: 2.25rem;
  color: #374151;
}

.hero-links {
  display: flex;
  gap: 1.5rem;
  align-items: center;
  flex-wrap: wrap;
}

.hero-links a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.15s;
}

.hero-links a:hover {
  color: var(--text);
}

/* ── Sections ── */

section:not(#hero) {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 4.5rem 1.5rem;
  border-top: 1px solid var(--border);
  scroll-margin-top: var(--header-h);
}

section h2 {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 2rem;
}

/* ── About ── */

#about p {
  font-size: 1rem;
  line-height: 1.75;
  margin-bottom: 1rem;
  max-width: 640px;
}

.credentials {
  list-style: none;
  margin-top: 1.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.credentials li {
  font-size: 0.875rem;
  color: var(--muted);
  padding-left: 1.25rem;
  position: relative;
}

.credentials li::before {
  content: '—';
  position: absolute;
  left: 0;
  color: var(--muted);
}

/* ── Projects ── */

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

.project-card {
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.25rem;
  transition: border-color 0.15s;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.project-card:hover {
  border-color: var(--accent);
}

.project-card h3 {
  font-size: 0.875rem;
  font-weight: 600;
}

.project-card h3 a {
  color: var(--text);
  text-decoration: none;
}

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

.project-card p {
  font-size: 0.825rem;
  color: var(--muted);
  line-height: 1.55;
  flex: 1;
}

.lang {
  font-size: 0.7rem;
  color: var(--muted);
  background: var(--border);
  padding: 0.2rem 0.5rem;
  border-radius: 3px;
  align-self: flex-start;
}

/* ── Badge & sub-list ── */

.badge {
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.1rem 0.4rem;
  margin-left: 0.4rem;
  vertical-align: middle;
}

.sub-list {
  list-style: none;
  margin-top: 0.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.sub-list li {
  font-size: 0.8rem;
  color: var(--muted);
  padding-left: 1rem;
  position: relative;
}

.sub-list li::before {
  content: '↳';
  position: absolute;
  left: 0;
  color: var(--border);
}

/* ── Research ── */

.research-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.research-item {
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: 1rem;
  align-items: start;
}

.research-type {
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  padding: 0.25rem 0.4rem;
  border: 1px solid var(--border);
  border-radius: 3px;
  text-align: center;
  margin-top: 0.15rem;
}

.research-details p {
  font-size: 0.875rem;
  line-height: 1.5;
}

.research-title {
  color: var(--text);
  font-weight: 500;
  margin-bottom: 0.2rem;
}

.research-venue {
  color: var(--muted);
  font-size: 0.8rem;
}

.research-note {
  margin-top: 2.5rem;
  font-size: 0.825rem;
  color: var(--muted);
}

/* ── Footer ── */

footer {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 4rem 1.5rem 5rem;
  border-top: 1px solid var(--border);
  scroll-margin-top: var(--header-h);
}

.footer-heading {
  font-size: 1.1rem;
  font-weight: 500;
  margin-bottom: 1rem;
}

.footer-links {
  display: flex;
  gap: 1.5rem;
  margin-top: 1rem;
}

.footer-links a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.15s;
}

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

.footer-note {
  margin-top: 3rem;
  font-size: 0.75rem;
  color: var(--muted);
}

/* ── Responsive ── */

@media (max-width: 768px) {
  #hero {
    padding: 4rem 1.5rem 3rem;
  }

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

  .research-item {
    grid-template-columns: 1fr;
    gap: 0.35rem;
  }

  .research-type {
    display: inline-block;
    width: auto;
  }

  footer {
    padding: 3rem 1.5rem 4rem;
  }
}

/* ── Dark theme ── */

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --text: #f1f5f9;
    --muted: #94a3b8;
    --accent: #60a5fa;
    --border: #334155;
  }

  .positioning {
    color: var(--text);
  }

  .project-card {
    background: #1e293b;
  }

  footer {
    background: #1e293b;
  }
}