Can someone assist me in creating a curved line with fading edges using css3/html5, similar to the design shown in this image https://i.sstatic.net/8GFk6.png
I came across this example on CodePen, but the edges are not fading as I would like them to.
.box{
width:500px; height:100px;
border:solid 5px #000;
border-color:#000 transparent transparent transparent;
border-radius: 50%/100px 100px 0 0;
}
<div class="box"></div>
Is there a way to achieve the desired effect?