.mask {
  display: none;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: #f5f5f5;
  opacity: 0.5;
}

.loading {
  display: block;
  position: absolute;
  top: 40%;
  left: 40%;
  width: 20%;
  height: 20%;
  text-align: center;
}