<!DOCTYPE html>
<html>
    <body>
        <p>You should see a solid green square below</p>
        <svg width="800px" height="800px" xmlns="http://www.w3.org/2000/svg">
            <defs>
                <clipPath id="clip-out-middle">
                  <rect x="160" y="160" width="80" height="80" />
                </clipPath>
            </defs>
            <rect x="160" y="160" width="80" height="80" fill="green" clip-path="url(#clip-out-middle)"/>
        </svg>
        </div>
    </body>
</html>