I am currently playing with and loving! eMag on localhost, it is your demo that is displaying the big black oval on my mobile. I cleared my phone’s cache and tried your updated version and this is what happens.
Opera Mini browser 
It’s working fine in Chrome now but this is what it looks like in Opera Mini browser
A Few other bugs:
- cannot change user admin to nickname or add other users.
- 404 duplicates title but that was an easy fix.
- Child theme takes a very long time to create even with find/replace
- I can’t remember where it was exactly but it was duplicating content. That one I’ll have to come back to.