.custom-tooltip {
  position: absolute;
  background: rgba(0,0,0,0.75);
  color: #fff;
  padding: 5px 8px;
  border-radius: 4px;
  font-size: 12px;
  pointer-events: none;
  white-space: nowrap;
  z-index: 9999;
  display: none;
}