MediaWiki:Common.css

.Spoiler {
  display: inline-block;
  cursor: pointer;
  color: black;                  /* text color when revealed */
  background-color: white;        /* background for contrast */
  border-radius: 4px;
  padding: 2px 4px;
  filter: blur(3px);             /* start blurred */
  transition: filter 0.3s ease, background-color 0.3s ease;
}

/* Reveal on hover */
.Spoiler:hover {
  filter: blur(0);               /* remove blur */
  background-color: white;        /* optional highlight */
}