:root {
  --research-bg: #0b1220;
  --research-card: rgba(15, 23, 42, 0.78);
  --research-border: rgba(148, 163, 184, 0.2);
  --research-text: #e2e8f0;
  --research-muted: rgba(226, 232, 240, 0.7);
  --research-accent: #38bdf8;
}

body.research-ai {
  background: var(--research-bg);
  color: var(--research-text);
}

body.research-ai::before {
  content: "";
  position: fixed;
  inset: 0;
  background:
    radial-gradient(circle at 20% 20%, rgba(56, 189, 248, 0.16), transparent 45%),
    radial-gradient(circle at 80% 10%, rgba(129, 140, 248, 0.12), transparent 55%);
  z-index: -2;
}

body.research-ai::after {
  content: "";
  position: fixed;
  inset: 0;
  background-image: radial-gradient(rgba(255, 255, 255, 0.45) 1px, transparent 1px);
  background-size: 140px 140px;
  opacity: 0.08;
  z-index: -1;
}

body.research-ai .navbar {
  background: rgba(11, 18, 32, 0.92);
  border-bottom: 1px solid rgba(148, 163, 184, 0.12);
}

body.research-ai .nav-links a,
body.research-ai .logo-link,
body.research-ai .nav-mobile a {
  color: var(--research-text);
}

body.research-ai .nav-links a::after {
  background: var(--research-accent);
}

body.research-ai .btn-primary {
  background: linear-gradient(120deg, #38bdf8, #2563eb);
  box-shadow: 0 14px 30px rgba(37, 99, 235, 0.35);
}

body.research-ai .btn-ghost {
  background: rgba(15, 23, 42, 0.6);
  color: var(--research-text);
  border-color: rgba(148, 163, 184, 0.3);
}

body.research-ai .nav-toggle span {
  background: var(--research-text);
}

.research-hub {
  width: min(1100px, 92%);
  margin: 0 auto;
  padding: 120px 0 90px;
}

.research-hero {
  margin-bottom: 50px;
}

.hero-tag {
  display: inline-flex;
  padding: 6px 14px;
  border-radius: 999px;
  background: rgba(56, 189, 248, 0.12);
  color: var(--research-accent);
  font-weight: 600;
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  margin-bottom: 16px;
}

.research-hero h1 {
  font-size: clamp(2.4rem, 4vw, 3.3rem);
  margin-bottom: 14px;
  color: #ffffff;
}

.research-hero p {
  font-size: 1.05rem;
  color: var(--research-muted);
  max-width: 700px;
}

.hero-actions {
  margin-top: 22px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}

.paper-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 22px;
  margin-bottom: 50px;
}

.paper-card {
  background: var(--research-card);
  border: 1px solid var(--research-border);
  border-radius: 20px;
  padding: 24px;
  box-shadow: 0 20px 50px rgba(2, 6, 23, 0.5);
}

.paper-card h2 {
  color: #ffffff;
  margin-bottom: 6px;
}

.paper-card span {
  font-size: 0.85rem;
  color: var(--research-muted);
}

.paper-card p {
  color: var(--research-muted);
  margin: 16px 0;
}

.paper-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.paper-viewer {
  margin-top: 30px;
}

.viewer-header h2 {
  color: #ffffff;
  margin-bottom: 8px;
}

.viewer-header p {
  color: var(--research-muted);
}

.viewer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 22px;
  margin-top: 24px;
}

.viewer-card {
  background: rgba(15, 23, 42, 0.75);
  border: 1px solid var(--research-border);
  border-radius: 20px;
  padding: 20px;
  box-shadow: 0 20px 50px rgba(2, 6, 23, 0.5);
}

.viewer-card h3 {
  color: #ffffff;
  margin-bottom: 12px;
}

.pdf-frame {
  width: 100%;
  height: 520px;
  border: none;
  border-radius: 14px;
  background: #0f172a;
}

.viewer-note {
  margin-top: 12px;
  font-size: 0.85rem;
  color: var(--research-muted);
}

@media (max-width: 900px) {
  .pdf-frame {
    display: none;
  }
}

@media (max-width: 720px) {
  .research-hub {
    padding: 100px 0 70px;
  }
}