<!doctype html>
<body style="zoom: 3">
  <style>
    span { display: inline-block;
           width: 100px;
           height: 100px;
           border-style: solid;
           border-image: radial-gradient(yellow, green) 35% / 30px }
  </style>
  <span></span>
  <span></span>
</body>