index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />

    <link
      rel="icon"
      type="image/png"
      sizes="96x96"
      href="/favicon/favicon-96x96.png"
    />

    <title>MSE</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }

      #app {
        text-align: center;
      }

      video {
        margin-top: 10vh;
        outline: none;
        width: 80vw;
        max-width: 500px;
      }
    </style>
  </head>
  <body>
    <div id="app">
      <video controls></video>
    </div>
    <script src="https://unpkg.com/mp4box@0.3.20/dist/mp4box.all.js"></script>
    <script src="/app.js" type="module"></script>
  </body>
</html>