iframe-responsive.html

<style>
    .iframe-container {
        background: #ccc;
        position: relative;
        height: 0;
        padding-bottom: 75%;  /* 4/3 on mobile, padding = 3/4 */
    }
    .iframe-container iframe {
        position: absolute;
        top: 0;
        left: 0; 
        width: 100%; 
        height: 100%;
    }

    @media all and (min-width: 24em) {
        .iframe-container {
            padding-bottom: 56.25%;  /* 16/9 on desktop, padding = 9/16 */
        }
    }
</style>
<script src="https://360player.io/static/dist/scripts/embed.js" async></script>

<div class="iframe-container">
    <iframe src="https://360player.io/p/k6f7rb/" frameborder="0" allowfullscreen data-token="k6f7rb"></iframe>
</div>