.hf_spinner {
      width: 40px;
      height: 40px;

      position: relative;
      margin: 100px auto;
    }

    .double-bounce1, .double-bounce2 {
      width: 100%;
      height: 100%;
      border-radius: 50%;
      background-color: #333;
      opacity: 0.6;
      position: absolute;
      top: 0;
      left: 0;
      
      -webkit-animation: bounce 2.0s infinite ease-in-out;
      animation: bounce 2.0s infinite ease-in-out;
    }

    .double-bounce2 {
      -webkit-animation-delay: -1.0s;
      animation-delay: -1.0s;
    }

    @-webkit-keyframes bounce {
      0%, 100% { -webkit-transform: scale(0.0) }
      50% { -webkit-transform: scale(1.0) }
    }

    @keyframes bounce {
      0%, 100% {
        transform: scale(0.0);
        -webkit-transform: scale(0.0);
      } 50% {
        transform: scale(1.0);
        -webkit-transform: scale(1.0);
      }
    }