RR0/rr0.org

.note-id {
  position: relative;
  text-decoration: none;
  padding: .2rem .3rem;
  font-style: normal;
  vertical-align: super;
  color: #069;
  font-size: smaller;
  line-height: normal;
  z-index: 1;
}

.note-contents {
  color: grey;
  display: none;
}

.note-id:hover {
  color: var(--link-color);
}

.note-id:hover .note-contents {
  position: absolute;
  margin-top: 1em;
  display: inline-block;
  padding: 0.35em 0.5em;
  color: var(--color);
  background: var(--background-color);
  box-shadow: var(--icon-color) 0.15em 0.15em 0.3em;
  border: 1px outset var(--icon-color);
  border-radius: 0.25em;
  z-index: 2;
}

.anchor:target + .note-contents {
  display: inline-block;
}