basecode

HTML

<html>

  <head>
  </head>

  <body>
    <button style="height: 30px; width: 255px;background-color:black;color:white" onclick="openGame()">open</button>
    <script>
      function openGame(){
        var win = window.open()
        var url = "https://blackscreen.app/"
        var iframe = win.document.createElement('iframe')
        iframe.style.width = "100%";
        iframe.style.height = "100%";
        iframe.style.border = "none";
        iframe.src = url
        win.document.body.appendChild(iframe)
      }

    </script>
  </body>

</html>