Create a div with rounded corners, double border, and a background of two overlapping linear gradients.
HTML
<div><span>X</span></div>
CSS
div{
width: 300px;
padding:1px;
border-radius: 20px;
border: solid 1px transparent;
background-image: linear-gradient(45deg, skyblue, skyblue),
linear-gradient(-33deg, red, transparent, transparent, red);
background-origin: border-box;
background-clip: content-box, border-box;
}
span {
display:block;
margin:10px;
}