.box {
      width: 200px;
      height: 200px;
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      overflow: hidden;
  }

  .box .b {
      border-radius: 50%;
      border-left: 4px solid;
      border-right: 4px solid;
      border-top: 4px solid transparent !important;
      border-bottom: 4px solid transparent !important;
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      animation: ro 2s infinite;
  }

  .box .b1 {
      border-color: #4A69BD;
      width: 120px;
      height: 120px;
  }

  .box .b2 {
      border-color: #F6B93B;
      width: 100px;
      height: 100px;
      animation-delay: 0.2s;
  }

  .box .b3 {
      border-color: #2ECC71;
      width: 80px;
      height: 80px;
      animation-delay: 0.4s;
  }

  .box .b4 {
      border-color: #34495E;
      width: 60px;
      height: 60px;
      animation-delay: 0.6s;
  }

  @keyframes ro {
      0% {
          transform: translate(-50%, -50%) rotate(0deg);
      }

      50% {
          transform: translate(-50%, -50%) rotate(-180deg);
      }

      100% {
          transform: translate(-50%, -50%) rotate(0deg);
      }
  }