html 部分

<div class="loader"></div>

css 部分

<style>
    .loader {
      position: relative;
      font-size: 12px;
      width: 2.5em;
      height: 2.5em;
      transform: rotate(165deg);
    }
    .loader:before, .loader:after {
      content: '';
      position: absolute;
      top: 50%;
      left: 50%;
      display: block;
      width: 0.5em;
      height: 0.5em;
      border-radius: 0.25em;
      transform: translate(-50%, -50%);
    }
    .loader:before {
      animation: before 2s infinite;
    }
    .loader:after {
      animation: after 2s infinite;
    }
    
    @keyframes before {
      0% {
        width: 0.5em;
        box-shadow: 1em -0.5em rgba(225, 20, 98, 0.75), -1em 0.5em rgba(111, 202, 220, 0.75);
      }
      35% {
        width: 2.5em;
        box-shadow: 0 -0.5em rgba(225, 20, 98, 0.75), 0 0.5em rgba(111, 202, 220, 0.75);
      }
      70% {
        width: 0.5em;
        box-shadow: -1em -0.5em rgba(225, 20, 98, 0.75), 1em 0.5em rgba(111, 202, 220, 0.75);
      }
      100% {
        box-shadow: 1em -0.5em rgba(225, 20, 98, 0.75), -1em 0.5em rgba(111, 202, 220, 0.75);
      }
    }
    @keyframes after {
      0% {
        height: 0.5em;
        box-shadow: 0.5em 1em rgba(61, 184, 143, 0.75), -0.5em -1em rgba(233, 169, 32, 0.75);
      }
      35% {
        height: 2.5em;
        box-shadow: 0.5em 0 rgba(61, 184, 143, 0.75), -0.5em 0 rgba(233, 169, 32, 0.75);
      }
      70% {
        height: 0.5em;
        box-shadow: 0.5em -1em rgba(61, 184, 143, 0.75), -0.5em 1em rgba(233, 169, 32, 0.75);
      }
      100% {
        box-shadow: 0.5em 1em rgba(61, 184, 143, 0.75), -0.5em -1em rgba(233, 169, 32, 0.75);
      }
    }
    
    .loader {
      position: relative;
    }
</style>

待续…