<!doctype HTML>
<style>
  * {
    margin: 0;
  }
  .el {
    width: 50px;
    height: 60px;
  }

</style>
<div style="isolation: isolate">
  <div class="el"
      style="position: absolute; z-index: 1; top: 40px; left: 10px; border: 1px solid black; background: lightblue"></div>
  <div class="el"
      style="position: absolute; z-index: 2; top: 5px; left: 5px; border: 1px solid black; background: lightgreen"></div>
</div>
<div id=top class="el" style="position: relative; background: lightgray; top: 50px"></div>
