:root {
  --site-bg: #f6f3ed;
  --site-surface: #fffdf8;
  --site-text: #262116;
  --site-muted: #6c6254;
  --site-soft: #8f8270;
  --site-accent: #2f6f67;
  --site-accent-2: #8a5b2f;
  --site-ink: #1c2630;
  --site-border: #ddd3c4;
  --site-shadow: 0 10px 28px rgba(44, 36, 22, 0.08);
  --site-radius: 8px;
}
html { scroll-behavior: smooth; }
body { text-rendering: optimizeLegibility; -webkit-font-smoothing: antialiased; }
.site-shell {
  min-height: 100vh;
  background:
    linear-gradient(180deg, rgba(246,243,237,0.94), rgba(246,243,237,1)),
    radial-gradient(circle at 14% 8%, rgba(47,111,103,0.09), transparent 28%),
    radial-gradient(circle at 86% 18%, rgba(138,91,47,0.08), transparent 28%);
  color: var(--site-text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
}
.kb-back-btn {
  position: fixed;
  bottom: 28px;
  left: 28px;
  z-index: 99999;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 40px;
  padding: 8px 18px;
  border: 1px solid rgba(138, 91, 47, 0.24);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.92);
  color: #7b4e2a;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
  text-decoration: none;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  font-size: 13px;
  line-height: 1.4;
  letter-spacing: 0.03em;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}
.kb-back-btn:hover,
.kb-back-btn:focus-visible {
  background: #fff;
  border-color: rgba(138, 91, 47, 0.42);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.12);
  color: #6f4424;
  transform: translateY(-2px);
  outline: none;
}
.site-btt {
  position: fixed;
  right: 22px;
  bottom: 22px;
  z-index: 500;
  width: 42px;
  height: 42px;
  border: 1px solid rgba(47, 111, 103, 0.24);
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.94);
  color: var(--site-accent);
  box-shadow: 0 8px 24px rgba(38, 33, 22, 0.12);
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(12px);
  transition: opacity 0.2s ease, transform 0.2s ease;
}
.site-btt.show { opacity: 1; pointer-events: auto; transform: translateY(0); }
.site-btt:focus-visible { outline: 2px solid var(--site-accent); outline-offset: 3px; }
@media (max-width: 680px) {
  .kb-back-btn { left: 16px; bottom: 16px; padding: 7px 14px; }
  .site-btt { right: 16px; bottom: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.001ms !important;
  }
}