index.html

<script>
window.RufflePlayer = window.RufflePlayer || {};
window.RufflePlayer.config = {
    "autoplay": "on",
    "splashScreen": false,
    "unmuteOverlay": "hidden",
};

function resizePlayer(player, aspectWidth, aspectHeight) {
    const containerHeight = window.innerHeight;
    const calculatedWidth = (containerHeight / aspectHeight) * aspectWidth;

    player.style.height = "100%";
    player.style.width = `${calculatedWidth}px`;

    if (calculatedWidth > window.innerWidth) {
        player.style.width = "100%";
        player.style.height = `${(window.innerWidth / aspectWidth) * aspectHeight}px`;
    }
}

window.addEventListener("load", (event) => {
    const ruffle = window.RufflePlayer.newest();
    const player = ruffle.createPlayer();
    const container = document.getElementById("container");
    container.appendChild(player);

    const urlParams = new URLSearchParams(window.location.search);
    const swfUrl = urlParams.get('url');
    const aspectRatio = urlParams.get('aspect');

    let aspectWidth = 4;
    let aspectHeight = 3;

    if (aspectRatio) {
        const [width, height] = aspectRatio.split(':').map(Number);
        if (!isNaN(width) && !isNaN(height)) {
            aspectWidth = width;
            aspectHeight = height;
        }
    }

    if (swfUrl) {
        player.load(swfUrl);
    } else {
        player.load("https://raw.githubusercontent.com/CodingKitten-YT/FlashEmbed/main/files/KittenGamez.swf");
    }

    resizePlayer(player, aspectWidth, aspectHeight);

    window.addEventListener('resize', () => {
        resizePlayer(player, aspectWidth, aspectHeight);
    });
});
</script>

<script src="https://unpkg.com/@ruffle-rs/ruffle"></script>
<div id="container" style="height:100vh;"></div>

<style>
  body {
    margin: 0;
    background-color: black;
  }
  #container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    width: 100vw;
    overflow: hidden;
  }
</style>