Quick question, is the problem in the app viewer or the IDE? At the moment we have an issue to address where theme CSS affects the IDE as well. High on our list of priorities to address.
Also, consider that we are using materialize, here is a link for their docs: http://materializecss.com/
So, looking at your theme, my guess is you are running in to an issue with CSS specificity, and being overridden by Materialize.
If you like, send us the screen so we can check it out.