<html>
    <head>
        <style>
            div {
                width: 200px;
                height: 200px;
            }

            span {
                position: absolute;
                opacity: 0;
            }

            .child {
                opacity: 0.7;
                background: green;
            }
            .container {
                opacity: 0.7;
            }
            body > div {
                opacity: 0.7;
            }
        </style>
    </head>
    <body>
        <div><span></span>
            <div class="container"><span></span>
                <div class="child"><span></span></div>
            </div>
        </div>
    </body>
</html>