If you store the html in the same place as the wiki this works
<iframe src='ApokalypseaufdemChromebook.html' frameborder="0" width="1024"; height="600"></iframe>
I would take it further and try embedding it except I do not speak German and its hard to understand as a result, but the links may be fooled by tiddlywikis own structure
If you are serving it on Node try tiddlywikiaddress/tiddlername when tiddler name is a html tiddler containing your game, at that address I believe the tiddler is presented as static html, rather than tiddlywikiaddress#tiddlername
I am not sure if this needs to be switched on somehow.
Regards
Tony