#back-to-top {
    background-color: #7FFF00;
    bottom: 0;
    box-shadow: 0 0 6px #7FFF00;
    color: #444444;
    padding: 7px 10px;
    position: fixed;
    right: 50px;
    cursor: pointer;
    font-size: 18px
}

.details,
.show,
.hide:target {
  display: none;
}
.hide:target + .show,
.hide:target ~ .details {
  display: block;
}