I cant get my index.html in express to show the styles.

This is my folder structure:

And then on server js I have this:

app.use(express.static(path.join(__dirname, '/public')));
app.use(useragent.express());

app.get('/', function(req, res){
  console.log('Listening on port ' + port)
  let isMobile = req.useragent.isMobile ? 'mobile' : 'desktop';
  console.log({isMobile})
  res.sendFile(path.resolve(__dirname + `/${isMobile}/index.html`));
});

And I just add the link tag on my html inside the head on the index.html like this:

  <link href="styles.css" rel="stylesheet" type="text/css">

The index I serve can be either inside the desktop or mobile folder But it doesnt get the styles... any idea whats the issue?

Thanks.