src/themes/loading-mask.scss
.widget.loading-mask {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  background: rgba(0,0,0,0.6);

  .loading {
    width: 150px;
    height: 15px;
    margin: 0 auto;
  }

  .loading span {
    display: inline-block;
    width: 15px;
    height: 100%;
    margin-right: 5px;
    border-radius: 50%;
    background: #b8e9ff;
    -webkit-animation: load 1.04s ease infinite;
  }

  .loading span:last-child {
    margin-right: 0;
  }

  @-webkit-keyframes load {
    0% {
      opacity: 1;
      transform: scale(1.3);
    }

    100% {
      opacity: 0.2;
      transform: scale(0.3);
    }
  }

  .loading span:nth-child(1) {
    -webkit-animation-delay: 0.13s;
  }

  .loading span:nth-child(2) {
    -webkit-animation-delay: 0.26s;
  }

  .loading span:nth-child(3) {
    -webkit-animation-delay: 0.39s;
  }

  .loading span:nth-child(4) {
    -webkit-animation-delay: 0.52s;
  }

  .loading span:nth-child(5) {
    -webkit-animation-delay: 0.65s;
  }
}
