In the Mobile interface beta there is a categories button but I think this is not very intuitive, most people will be just too lazy to explore it. Instead, please, we could try to expose the first 2-3 categories with a 'More...' button next to them.
Instead of this one line (with the categories button bringing up a popup which hides the page):
[Read in another language] [Categories]
Put these two lines (in any order):
[Read in another language]
<Equations> <Thermodynamic equations> [More categories...]