Slack style loader

slack-loader.html

<div class="demo-holder">
<div class="loader"></div>

<style>
.loader {
  margin: 0 auto;
  position: relative;
  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);
  }
}
</style>
</div>