[data-tooltip] {
  position: relative;
}

[data-tooltip]::before {
  content: attr(data-tooltip);
  visibility: hidden;
  width: 120px;
  background-color: #000000c0;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px 0;
  position: absolute;
  z-index: 1;
  top: 2%;
  left: 50%;
  margin-left: -60px;
  display: inline-block;
  opacity: 0;
  transition: opacity 0.3s;
}

[data-tooltip]:hover::before, [data-tooltip].tooltipShown::before {
  visibility: visible;
  opacity: 1;
}