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I solved it on May 5, 2021. You can try to beat my record on CSSBattle!

492 chars

<div a>
  <div t></div>
  <div b></div>
  <div k></div>
</div>
<style>
  body {
    background: #6592cf;
  }
  div {
    background: #243d83;
  }
  div > div {
    position: absolute;
    border-radius: 50%;
  }
  div[a] {
    margin: 75 42;
    height: 150;
    display: flex;
    justify-content: center;
    align-items: center;
  }
  div[k] {
    background: #eeb850;
    padding: 25;
  }
  div[b] {
    padding: 75;
  }
  div[t] {
    background: #6592cf;
    padding: 125;
  }
</style>