Evil Triangles

<div>
  <div></div>
  <div></div>
</div>
<style>
  body {
    background: #191919;
    display: grid;
    place-content: center;
  }
  div {
    width: 200px;
    height: 150px;
    display: flex;
    overflow: hidden;
  }

  div > div {
    background: #4f77ff;
    width: 100px;
    height: 100px;
    translate: 0 -70px;
    rotate: 45deg;
    box-shadow:
      35px 35px #191919,
      65px 65px #4f77ff,
      70px 70px #4f77ff;
  }
</style>