example.html

<!DOCTYPE HTML>
<html>
    <head>
        <meta charset='utf8'>
    <title>TEMPLATE</title>
    </head>
    <style>
      html, body {
        margin: 0;
        padding: 0;
        width: 100%;
        height: 100%;
        overflow: hidden;
      }
      #ruffle {
        width: 100%;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <div id="ruffle"></div>
    <script src="/RUFFLE/ruffle.js"></script>
    <script>
      window.RufflePlayer = window.RufflePlayer || {};
      window.addEventListener("load", (event) => {
        const ruffle = window.RufflePlayer.newest();
        const player = ruffle.createPlayer();
        const container = document.getElementById("ruffle");
        player.id = "player";
        player.style.width = "100%";
        player.style.height = "100%";
        container.appendChild(player);
        player.load("GAMENAME.swf");
      });
    </script>
  </body>
</html>