:root {
  --c-hero: #eef4ff;
  --c-models: #f1f5fd;
  --c-data: #fdf9f1;
  --c-play: #f1fdf4;
  --c-eval: #fdf1f7;
  --c-accent: #3b5bfe;
  --c-text: #1f2937;
  --radius: 12px;
}

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  color: var(--c-text);
  background: #ffffff;
}

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

/* Layout */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

section { padding: 72px 0; }

h1, h2 { margin: 0 0 16px; font-weight: 700; }
h1 { font-size: 2.75rem; line-height: 1.2; }
h2 { font-size: 1.85rem; }

/* Navigation */
.nav {
  position: sticky;
  top: 0;
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.85);
  border-bottom: 1px solid #e5e7eb;
  z-index: 100;
}
.nav .container { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: 12px 1.25rem; }
.nav-brand { display: inline-flex; align-items: center; gap: 10px; color: var(--c-text); font-weight: 700; }
.nav-brand img { height: 28px; width: auto; object-fit: contain; }
.nav-links { display: flex; align-items: center; gap: 6px; }
.nav-links a { color: #374151; font-weight: 600; padding: 8px 10px; border-radius: 8px; }
.nav-links a:hover { background: #f3f4f6; }

/* Light style for top-right Paper button only */
.nav-links .btn {
  background: #eef2ff;
  color: #1f2937;
  border: 1px solid #e5e7eb;
  box-shadow: none;
}
.nav-links .btn:hover {
  background: #e0e7ff;
  box-shadow: none;
  transform: none;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin: 8px 12px 8px 0;
  padding: 12px 16px;
  background: var(--c-accent);
  color: #fff;
  border-radius: 10px;
  font-weight: 700;
  box-shadow: 0 1px 2px rgba(0,0,0,0.06), 0 8px 24px rgba(59,91,254,0.25);
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 4px 12px rgba(0,0,0,0.08), 0 12px 28px rgba(59,91,254,0.28); }
.btn:active { transform: translateY(0); }
.btn:focus-visible { outline: none; box-shadow: 0 0 0 3px rgba(59,91,254,0.35); }

/* Grid & Cards */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.card {
  background: #fff;
  border: 1px solid #e5e7eb;
  border-radius: var(--radius);
  padding: 20px;
  min-height: 180px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.04);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 10px 24px rgba(0,0,0,0.06); border-color: #d1d5db; }

/* Hero */
.hero-title { display: flex; align-items: center; gap: 0; flex-wrap: wrap; justify-content: center; }
.hero-title img { height: 40px; width: auto; margin: 0; }
.hero-title img.hero-shield { height: 96px; margin-right: -18px; }
.hero-title h1 { margin: 0; font-size: 3rem; line-height: 1.2; font-weight: 800; }
.hero-center { max-width: 900px; margin: 0 auto; text-align: center; }

.title-figure { margin: 12px auto 8px; }
.title-figure img { max-width: 820px; width: 100%; height: auto; display: block; margin: 0 auto; }
/* Divider below equal contribution */
.hero-sep { border: none; height: 2px; background: #1f2937; max-width: 900px; margin: 14px auto 18px; border-radius: 2px; }

/* Author typography */
#authors { font-size: 1.15rem; line-height: 1.7; letter-spacing: 0.1px; display: inline-block; }
.authors-box {
  background: #E6C7AF;
  border: 1px solid #d7b091;
  border-radius: 12px;
  padding: 12px 18px;
  display: block;
  max-width: 900px;
  width: 100%;
  margin: 8px auto;
}
.authors .author { display: inline-block; margin: 0 34px; }
.authors-box, .authors-box * { color: #1f2937; }
@media (max-width: 768px) { .authors .author { margin: 0 14px; } }
.hero-center p { margin: 10px 0; }

.callout {
  background: #f8fafc;
  border: 1px solid #e5e7eb;
  border-left: 4px solid var(--c-accent);
  border-radius: 10px;
  padding: 16px;
  margin: 16px auto;
  max-width: 900px;
}

footer {
  text-align: center;
  padding: 32px 1.5rem;
  font-size: 0.95rem;
  color: #6b7280;
  background: #f9fafb;
}

/* Mobile navigation */
.nav-mobile { display: none; }
.hamburger { display: none; }
.mobile-menu {
  display: none;
  position: fixed; inset: 0; background: #fff; padding: 32px; flex-direction: column; gap: 20px;
  transform: translateX(100%); transition: transform 0.3s ease; z-index: 200;
}
.mobile-menu.active { transform: translateX(0); }
.close-menu { align-self: flex-end; background: none; border: none; font-size: 1.5rem; cursor: pointer; }
.mobile-menu a { font-size: 1.25rem; font-weight: 600; padding: 12px 0; border-bottom: 1px solid #e5e7eb; }

.backdrop { position: fixed; inset: 0; background: rgba(0,0,0,0.25); opacity: 0; pointer-events: none; transition: opacity 0.2s ease; z-index: 150; }
.backdrop.active { opacity: 1; pointer-events: auto; }
body.scroll-locked { overflow: hidden; }

/* Mobile */
@media (max-width: 768px) {
  .nav { display: none; }
  .nav-mobile { display: flex; justify-content: space-between; align-items: center; position: sticky; top: 0; backdrop-filter: blur(12px); background: rgba(255,255,255,0.92); border-bottom: 1px solid #e5e7eb; padding: 12px 20px; z-index: 100; }
  .nav-logo { display: flex; align-items: center; gap: 8px; font-weight: 700; font-size: 1.1rem; }
  .nav-logo img { height: 24px; width: auto; object-fit: contain; }
  .hamburger { display: block; cursor: pointer; background: none; border: none; font-size: 1.5rem; padding: 8px; }

  section { padding: 56px 0; }
  .hero-title h1 { font-size: 2.1rem; }
}

/* Desktop tweaks */
@media (min-width: 900px) {
  .hero-title { flex-wrap: nowrap; }
}