<!doctype HTML>
<style>
  .outer {
    position:relative;
    width: 120px;
    height: 120px;
    border-radius: 40px;
    background-color: rgba(255,0,0,0.5);
  }

  .inner {
    position:absolute;
    top:10px;
    left:10px;
    width: 100px;
    height: 100px;
    border-radius: 30px;
    background-color: lightblue;
  }
</style>
<div class = "outer">
    <div class = "inner"></div>
</div>
