.us-backdrop {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 1002;
  background: rgba($c-blue, .5);
  opacity: 0;
  visibility: hidden;
}

.us-backdrop--animated {
  transition: opacity 0.5s;
}

.us-backdrop--visible {
  visibility: visible;
}

.us-backdrop--active {
  opacity: 1;
}