.overlay {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(0, 0, 0, 0.7);
  transition: opacity 400ms;
  visibility: hidden;
  opacity: 0;
  z-index: 1010;
}
.overlay:target {
  visibility: visible;
  opacity: 1;
}

.popup {
  margin: 70px auto;
  padding: 25px;
  background: #fff;
  border-radius: 5px;
  width: 520px;
  position: relative;
}

.popup .close {
  position: absolute;
  top: 6px;
  right: 7px;
  font-size: 21px;
  font-weight: bold;
  text-decoration: none;
  color: #666;
}
.popup .close:hover {
  color: #a00;
}