mask-size-contain-ref.html

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<!DOCTYPE html>

<html>

  <head>

    <meta charset="utf-8">

    <title>CSS Masking: mask-size: mask layer size</title>

    <link rel="author" title="Astley Chen" href="mailto:aschen@mozilla.com">

    <link rel="author" title="Mozilla" href="https://www.mozilla.org">

    <style type="text/css">

      #outer {

        border: 10px solid black;

        width: 64px;

        height: 128px;

      #inner {

        width: 64px;

        height: 64px;

        background-color: purple;

    </style>

  </head>

  <body>

    <div id="outer">

      <div id="inner"></div>

    </div>

  </body>

</html>