Tesseract

<div class="rectangle"></div>
<div class="square"></div>

<style>
  * {
    margin: 0;
  }
  body {
    background: #222730;
    display: grid;
    place-items: center;
  }

  .rectangle {
    width: 100%;
    height: 150px;
    background: #4caab3;
  }

  .square {
    background: #4caab3;
    height: 150px;
    width: 150px;
    position: absolute;
    rotate: 45deg;
    box-shadow: 0 0 0 50px #222730;
  }

  .square::after {
    content: '';
    width: 50px;
    height: 50px;
    background: #393e46;
    position: absolute;
    top: 50%;
    left: 50%;
    translate: -50% -50%;
    border-radius: 50%;
  }
</style>