.research-return {
  position: fixed;
  right: clamp(16px, 2.4vw, 34px);
  bottom: max(18px, env(safe-area-inset-bottom));
  z-index: 120;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  min-height: 44px;
  padding: 0 17px;
  border: 1px solid rgba(255, 255, 255, .5);
  border-radius: 999px;
  color: #f7f4ee;
  background: rgba(20, 19, 17, .72);
  box-shadow: 0 10px 34px rgba(0, 0, 0, .2);
  -webkit-backdrop-filter: blur(16px) saturate(115%);
  backdrop-filter: blur(16px) saturate(115%);
  font: 500 12px/1 "Noto Sans SC", "Microsoft YaHei", Arial, sans-serif;
  letter-spacing: .04em;
  text-decoration: none;
  transition: transform .22s ease, background .22s ease, border-color .22s ease;
}
.research-return::before { content: "←"; font-size: 15px; }
.research-return:hover,
.research-return:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(255, 255, 255, .85);
  background: rgba(12, 12, 11, .88);
  outline: none;
}
@media (max-width: 640px) {
  .research-return { right: 12px; bottom: max(12px, env(safe-area-inset-bottom)); min-height: 42px; padding: 0 14px; }
}
@media (prefers-reduced-motion: reduce) { .research-return { transition: none; } }