/* ==========================================================================
   Geunhyuk Youk — personal academic page
   Fixed (sticky) profile sidebar + scrolling content
   Light/dark themes via CSS custom properties
   ========================================================================== */

/* ---------- Theme tokens ---------- */
:root {
  --bg: #f8fafc;
  --bg-elev: #ffffff;
  --bg-soft: #eef2f7;
  --text: #0f172a;
  --text-soft: #475569;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --accent-1: #6366f1;   /* indigo */
  --accent-2: #06b6d4;   /* cyan   */
  --accent-soft: rgba(99, 102, 241, 0.10);
  --oral: #f97316;
  --oral-soft: rgba(249, 115, 22, 0.12);
  --shadow: 0 1px 3px rgba(15, 23, 42, 0.06), 0 8px 24px rgba(15, 23, 42, 0.06);
  --shadow-lg: 0 4px 12px rgba(15, 23, 42, 0.08), 0 16px 48px rgba(15, 23, 42, 0.12);
  --nav-bg: rgba(248, 250, 252, 0.8);
  --teaser-bg: #ffffff;
}

[data-theme="dark"] {
  --bg: #0b0e14;
  --bg-elev: #121722;
  --bg-soft: #1a2130;
  --text: #e6eaf2;
  --text-soft: #a3adc2;
  --text-muted: #5d6b85;
  --border: #232c3e;
  --accent-1: #818cf8;
  --accent-2: #22d3ee;
  --accent-soft: rgba(129, 140, 248, 0.14);
  --oral: #fb923c;
  --oral-soft: rgba(251, 146, 60, 0.16);
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.5), 0 16px 48px rgba(0, 0, 0, 0.45);
  --nav-bg: rgba(11, 14, 20, 0.75);
  --teaser-bg: #f4f6fa; /* paper figures stay on light background */
}

/* ---------- Base ---------- */
* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; scroll-padding-top: 84px; }

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.65;
  background: var(--bg);
  color: var(--text);
  transition: background-color 0.3s ease, color 0.3s ease;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, .brand-name {
  font-family: "Sora", "Inter", sans-serif;
  line-height: 1.25;
}

a { color: var(--accent-1); text-decoration: none; }
a:hover { text-decoration: underline; }

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- Nav ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}

.nav-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  font-weight: 700;
}
.brand:hover { text-decoration: none; }

.brand-mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  color: #fff;
  font-family: "Sora", sans-serif;
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.02em;
}

.brand-name { font-size: 1rem; font-weight: 700; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-link {
  padding: 8px 12px;
  border-radius: 8px;
  color: var(--text-soft);
  font-size: 0.925rem;
  font-weight: 500;
}
.nav-link:hover { color: var(--text); background: var(--bg-soft); text-decoration: none; }
.nav-link.active { color: var(--accent-1); background: var(--accent-soft); }

.nav-cv {
  margin-left: 8px;
  padding: 7px 16px;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  color: #fff;
  font-size: 0.875rem;
  font-weight: 600;
}
.nav-cv:hover { text-decoration: none; filter: brightness(1.08); }

.nav-actions { display: flex; align-items: center; gap: 8px; }

.theme-toggle {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-elev);
  color: var(--text-soft);
  cursor: pointer;
  transition: color 0.2s, border-color 0.2s;
}
.theme-toggle:hover { color: var(--accent-1); border-color: var(--accent-1); }

.icon-moon { display: none; }
[data-theme="dark"] .icon-sun { display: none; }
[data-theme="dark"] .icon-moon { display: block; }

.nav-burger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 38px;
  height: 38px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-elev);
  cursor: pointer;
}
.nav-burger span {
  display: block;
  width: 16px;
  height: 2px;
  margin: 0 auto;
  border-radius: 2px;
  background: var(--text-soft);
}

/* ---------- Layout: sidebar + content ---------- */
.layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 56px;
  align-items: start;
  padding-top: 48px;
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: sticky;
  top: 96px;
  text-align: center;
}

.photo-frame {
  width: 100%;
  max-width: 240px;
  margin: 0 auto 20px;
  aspect-ratio: 4 / 5;
  border-radius: 20px;
  padding: 4px;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  box-shadow: var(--shadow-lg);
}

.photo-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 17px;
  display: block;
}

.side-name {
  font-size: 1.45rem;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.side-role {
  margin-top: 4px;
  color: var(--text-soft);
  font-size: 0.95rem;
  font-weight: 500;
}

.side-affil {
  color: var(--text-soft);
  font-size: 0.9rem;
}

.side-email {
  display: inline-block;
  margin-top: 12px;
  font-size: 0.875rem;
  font-weight: 600;
}

.side-icons {
  display: flex;
  justify-content: center;
  gap: 10px;
  margin-top: 16px;
}

.side-icons a {
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--bg-elev);
  color: var(--text-soft);
  box-shadow: var(--shadow);
  transition: color 0.15s, border-color 0.15s, transform 0.15s;
}
.side-icons a:hover {
  color: var(--accent-1);
  border-color: var(--accent-1);
  transform: translateY(-2px);
}

/* ---------- Sections ---------- */
.content { min-width: 0; }

.section { padding: 0 0 56px; }

.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.section-title {
  display: flex;
  align-items: center;
  gap: 14px;
  font-size: 1.55rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 24px;
}

.section-bar {
  width: 30px;
  height: 6px;
  border-radius: 3px;
  background: linear-gradient(90deg, var(--accent-1), var(--accent-2));
}

.section-side-link { font-size: 0.9rem; font-weight: 600; }

/* ---------- About ---------- */
.about-bio p { color: var(--text-soft); margin-bottom: 12px; max-width: 64ch; }
.about-bio strong { color: var(--text); }

.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 18px; }

.chip {
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-elev);
  color: var(--text-soft);
  font-size: 0.8rem;
  font-weight: 500;
}

/* ---------- News ---------- */
.news-list { list-style: none; }

.news-item {
  display: flex;
  align-items: baseline;
  gap: 18px;
  padding: 12px 0;
  border-bottom: 1px dashed var(--border);
}
.news-item:last-child { border-bottom: none; }

.news-date {
  flex: 0 0 84px;
  padding: 3px 10px;
  border-radius: 8px;
  background: var(--accent-soft);
  color: var(--accent-1);
  font-size: 0.78rem;
  font-weight: 700;
  text-align: center;
  white-space: nowrap;
}

.news-item p { color: var(--text-soft); }
.news-item strong { color: var(--text); }

/* ---------- Publications ---------- */
.pub-list { display: flex; flex-direction: column; gap: 20px; }

.pub-card {
  display: grid;
  grid-template-columns: 232px 1fr;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--bg-elev);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.pub-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-1);
}

.pub-teaser {
  display: grid;
  place-items: center;
  background: var(--teaser-bg);
  border-right: 1px solid var(--border);
  padding: 14px;
  min-height: 160px;
}

.pub-teaser img {
  max-width: 100%;
  max-height: 170px;
  object-fit: contain;
  border-radius: 6px;
}

.pub-body { padding: 20px 24px; }

.pub-badges { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 10px; }

.badge {
  padding: 3px 12px;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}
.badge-accent {
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  color: #fff;
}
.badge-conf { background: var(--accent-soft); color: var(--accent-1); }
.badge-journal { background: rgba(6, 182, 212, 0.12); color: #0891b2; }
[data-theme="dark"] .badge-journal { color: #22d3ee; }
.badge-oral { background: var(--oral-soft); color: var(--oral); }

.pub-title {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.pub-authors {
  color: var(--text-soft);
  font-size: 0.9rem;
  margin-bottom: 2px;
}
.pub-authors strong { color: var(--text); }

.pub-venue {
  color: var(--text-muted);
  font-size: 0.85rem;
  font-style: italic;
  margin-bottom: 12px;
}

.pub-links { display: flex; flex-wrap: wrap; gap: 8px; }

.pub-links a {
  padding: 5px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text-soft);
  font-size: 0.8rem;
  font-weight: 600;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}
.pub-links a:hover {
  text-decoration: none;
  color: var(--accent-1);
  border-color: var(--accent-1);
  background: var(--accent-soft);
}

.pub-footnote { margin-top: 16px; color: var(--text-muted); font-size: 0.85rem; }

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

.service-card {
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--bg-elev);
  box-shadow: var(--shadow);
}

.service-card h3 {
  font-size: 1rem;
  margin-bottom: 12px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--accent-soft);
}

.service-card ul { list-style: none; }
.service-card li {
  color: var(--text-soft);
  font-size: 0.9rem;
  padding: 5px 0 5px 18px;
  position: relative;
}
.service-card li::before {
  content: "";
  position: absolute;
  left: 2px;
  top: 14px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
}

/* ---------- Education timeline ---------- */
.timeline {
  position: relative;
  padding-left: 28px;
}
.timeline::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: linear-gradient(180deg, var(--accent-1), var(--accent-2));
  opacity: 0.35;
}

.timeline-item { position: relative; padding-bottom: 28px; }
.timeline-item:last-child { padding-bottom: 0; }

.timeline-dot {
  position: absolute;
  left: -28px;
  top: 5px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  border: 3px solid var(--bg);
}

.timeline-period {
  color: var(--accent-1);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}

.timeline-content h3 { font-size: 1.05rem; margin: 4px 0 2px; }
.timeline-content p { color: var(--text-soft); font-size: 0.9rem; }

/* ---------- Footer ---------- */
.footer {
  margin-top: 24px;
  padding: 28px 0;
  border-top: 1px solid var(--border);
  text-align: center;
}

.footer-copy { color: var(--text-muted); font-size: 0.85rem; }

/* ---------- Reveal on scroll ---------- */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.visible { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
}

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
    gap: 40px;
    padding-top: 36px;
  }

  .sidebar { position: static; }
  .photo-frame { max-width: 200px; }

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

  .nav-links {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    display: none;
    flex-direction: column;
    align-items: stretch;
    padding: 12px 24px 18px;
    background: var(--nav-bg);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--border);
  }
  .nav-links.open { display: flex; }
  .nav-link { padding: 12px; }
  .nav-cv { margin: 8px 12px 0; text-align: center; }

  .nav-burger { display: flex; }
  .brand-name { display: none; }
}

@media (max-width: 640px) {
  .pub-card { grid-template-columns: 1fr; }

  .pub-teaser {
    border-right: none;
    border-bottom: 1px solid var(--border);
    min-height: 0;
  }
  .pub-teaser img { max-height: 150px; }

  .news-item { flex-direction: column; gap: 6px; }
  .news-date { align-self: flex-start; }
}