Stairway

<div></div>
<style>
  body {
    background: #191919;
    display: grid;
    place-content: center;
  }
  div {
    width: 100px;
    height: 150px;
    background: #4f77ff;
    border-radius: 50px 50px 0 0;
    position: relative;
    overflow: hidden;
  }

  div::after {
    content: '';
    width: 80px;
    height: 20px;
    background: #191919;
    position: absolute;
    right: 0;
    bottom: 0;

    box-shadow:
      20px -24px #191919,
      40px -48px #191919,
      60px -72px #191919;
  }
</style>