/* Shared by all original BoBo pages. */
html { scrollbar-gutter: stable; }
.site-header { font-family: var(--font-sans); line-height: 1.5; }
.site-header .header-inner {
  width: min(1200px, calc(100% - 48px));
  min-height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.site-header .brand { flex-shrink: 0; }
.site-header .brand-image {
  display: block;
  width: 34px;
  height: 34px;
  border-radius: 8px;
  object-fit: cover;
  box-shadow: 0 0 0 1px rgba(213, 222, 255, .18), 0 7px 22px rgba(111, 127, 255, .16);
}
.site-header .site-nav {
  display: flex;
  align-items: center;
  gap: 28px;
  margin-left: auto;
  white-space: nowrap;
}
.site-header .site-nav a {
  padding: 6px 0;
  font: 500 13.5px/1.5 var(--font-sans);
  letter-spacing: normal;
}
.site-header .header-actions {
  display: flex;
  flex-shrink: 0;
  align-items: center;
  gap: 12px;
}
.site-header .theme-toggle, .site-header .header-cta { width: 38px; height: 38px; }
.site-header .theme-toggle:hover, .site-header .header-cta:hover { transform: none; }
@media (max-width: 900px) {
  .site-header .site-nav { display: none; }
}
@media (max-width: 640px) {
  .site-header .header-inner { width: calc(100% - 32px); }
}

/* Back to Top Floating Button */
.back-to-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  z-index: 90;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--line-strong);
  background: var(--surface-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  color: var(--muted);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(16px);
  transition: all 0.28s cubic-bezier(0.16, 1, 0.3, 1);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  color: var(--signal);
  border-color: var(--signal);
  transform: translateY(-3px);
  box-shadow: 0 8px 24px var(--signal-glow);
}

.back-to-top svg {
  width: 18px;
  height: 18px;
  transition: transform 0.2s ease;
}

.back-to-top:hover svg {
  transform: translateY(-2px);
}