Belle icon shape in CSS

Question

How can I draw this Belle icon shape in CSS only?

I've tried the border-radius on a square element but not getting the exact corners.

Answer 1

Well, in order to achieve the exact effect, we cannot rely on a single element even if we use percentage on border-radius.

So one option could be using two (pseudo-)elements overlapping each other where one of them is rotated by 90deg:

div {
  width: 300px;
  height: 300px;
  
  /* Just for demo */
  width: 95vmin; height: 95vmin;
  
  position: relative;
}

div:after, div:before {
  content: "";
  background: teal;
  position: absolute;
  top: 0;
  left: 8%;
  right: 8%;
  bottom: 0;
  border-radius: 50% / 22%;
}

div:before {
  transform: rotate(-90deg); /* vendor prefixes omitted due to brevity */
}

<div></div>

Answer 2

If you want the exact shape, you'd be better off using SVG. See for example :

<svg version="1.1" height="200" width="200" viewBox="0 0 30 30">
  <path d="M15 0 Q0 0 0 15 T15 30 30 15 15 0" fill="#249B57" stroke="none" />
</svg>

This uses a path with Quadratic beziers (Q)