<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>CSS Masking: mask-image: multiple SVG masks</title>
    <link rel="author" title="CJ Ku" href="mailto:cku@mozilla.com">
    <link rel="author" title="Mozilla" href="https://www.mozilla.org">
    <svg height="0">
      <mask id="mask" x="0" y="0" width="1" height="1">
        <rect x="0" y="0" width="50" height="50" style="stroke:none; fill: #ffffff"/>
        <circle cx="50" cy="50" r="25" style="stroke:none; fill: #ffffff"/>
      </mask>
    </svg>
    <style type="text/css">
      div {
        background-color: purple;
        mask: url(#mask);
        width: 100px;
        height: 100px;
      }
    </style>

  </head>

  <body>
    <div></div>
  </body>
</html>