Template:Spoiler Text/styles.css

.spoiler-text {
  position: relative;
  color: transparent;
  background-color: #343434;
  cursor: pointer;
  padding: 5px;
  border-radius: 5px;
}

.spoiler-text::after {
  color: #fff;
  content: attr(data-hidden);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.spoiler-text:focus {
  background-color: inherit;
  color: inherit;
}

.spoiler-text:focus::after {
  content: '';
}