/* Site Header & Navbar */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-height);
  background-color: rgba(9, 13, 22, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: background-color var(--transition-smooth), border-color var(--transition-smooth);
}

:root[data-theme="light"] .site-header {
  background-color: rgba(255, 255, 255, 0.85);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.brand-wrapper {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.brand-logo {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  object-fit: contain;
}

.brand-name {
  font-size: 1.125rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.version-pill {
  font-size: 0.6875rem;
  font-family: var(--font-mono);
  font-weight: 600;
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-full);
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
}

/* Nav Menu */
.nav-menu {
  display: flex;
  align-items: center;
  gap: 1.75rem;
  list-style: none;
}

.nav-link {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
  color: var(--text-primary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

/* Theme Toggle Button */
.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  background-color: var(--bg-surface);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.btn-icon:hover {
  color: var(--text-primary);
  border-color: var(--border-color-focus);
  background-color: var(--bg-surface-hover);
}

.btn-icon svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
}

/* Mobile Toggle */
.mobile-toggle {
  display: none;
  min-width: 44px;
  min-height: 44px;
}

@media (max-width: 860px) {
  .nav-menu {
    display: none;
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background-color: var(--bg-surface);
    border-bottom: 1px solid var(--border-color);
    padding: 1.25rem 1rem;
    flex-direction: column;
    align-items: stretch;
    gap: 0.35rem;
    box-shadow: 0 16px 32px -4px rgba(0, 0, 0, 0.12);
    z-index: 49;
    max-height: calc(100vh - var(--header-height));
    overflow-y: auto;
  }

  .nav-menu.open {
    display: flex;
    animation: slideDownMenu 0.22s cubic-bezier(0.16, 1, 0.3, 1) forwards;
  }

  .nav-menu .nav-link {
    display: block;
    width: 100%;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    min-height: 44px;
    display: flex;
    align-items: center;
  }

  .nav-menu .nav-link:hover,
  .nav-menu .nav-link:active {
    background-color: var(--bg-surface-hover);
  }

  .mobile-toggle {
    display: inline-flex;
  }
}

@keyframes slideDownMenu {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Hero Overview Section Background */
#overview {
  position: relative;
  overflow: hidden;
  background: radial-gradient(ellipse 70% 45% at 50% 0%, rgba(59, 130, 246, 0.08) 0%, transparent 70%);
}

/* Site Footer (Elevated Modern Design) */
.site-footer {
  margin-top: auto;
  border-top: 1px solid var(--border-color);
  background-color: var(--bg-surface);
  padding: 2.5rem 0;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.footer-left {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.footer-left img {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
  border: 1px solid var(--border-color);
}

.footer-nav {
  display: flex;
  align-items: center;
  gap: 1.75rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-nav li {
  list-style: none;
}

.footer-nav a {
  color: var(--text-secondary);
  font-weight: 500;
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-nav a:hover {
  color: var(--brand-primary);
}