Yeah, I'm asking a friend of mine if he knows about the xnb files, I get the feeling it's some wonky codec that's not included by default with wine for trademark reasons! If we can figure out the weird .zip issue, you could probably add in some code that catches the exception, parses it for the error code mentioned earlier, and subsequently disable audio, so that way there's a unified download that itch can easily snag (common usage is to only mark it "windows", itch on linux is more than happy to run it through wine, and gives the requisite caveat emptor that is sadly still sometimes needed with wine :P )