This problem is with Mantra 2.0.1. I am using a lot of custom CSS (input into the Mantra Settings -> Miscellaneous Settings CSS box) to customize the look and feel of my Mantra site. Overall, it's working the way I need it to, but when Mantra transitions into "Mobile" mode, style-mobile.css trumps my settings, keeping me from customizing the behavior without modifying either the PHP or the mobile-styles.css file. In a few cases I've been able to overcome this by creating a more specific selector, but I have several cases where this isn't possible.
Is mobile-styles.css loaded by JS after the page is loaded? Is that why it wins all the time? I need some workaround. If the only answer is "hack the theme PHP or CSS files", so be it. It won't be the first time, I'm just wanting to avoid that for all the obvious reasons.