#mover-topo-btn {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 9999;
  display: none;
  align-items: center;
  justify-content: center;
  border: none;
  border-radius: 50%;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
  background: none;
  padding: 0;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s, transform 0.3s;
}
#mover-topo-btn img, #mover-topo-btn svg {
  display: block;
  max-width: 70%;
  max-height: 70%;
  margin: auto;
}
@media (max-width: 600px) {
  #mover-topo-btn {
    right: 12px;
    bottom: 12px;
    width: 40px;
    height: 40px;
  }
}