Windmill

<div></div>
<div></div>
<div></div>
<div></div>

<style>
  body {
    background: #191919;
    display: grid;
    place-content: center;
    grid-template-columns: auto auto;
  }

  div {
    height: 100px;
    width: 50%;
  }

  div:nth-child(1),
  div:nth-child(4) {
    background: #f9e492;
    height: 50px;
    width: 100px;
  }

  div:nth-child(2),
  div:nth-child(3) {
    background: #4f77ff;
  }

  div:nth-child(1) {
    border-radius: 100px 100px 0 0;
    align-self: end;
  }

  div:nth-child(2) {
    border-radius: 0 100px 100px 0;
  }

  div:nth-child(3) {
    border-radius: 100px 0 0 100px;
    justify-self: end;
  }

  div:nth-child(4) {
    border-radius: 0 0 100px 100px;
  }
</style>