This page is unreadable on iPhone Safari.
For instance if you use white text with a white background while it may be a valid HTML document, it's not particularly useful for being able to read the information contained.
Even on Chrome the page is difficult to navigate.
In the larger sense, a comment that a given page doesn't work for a given platform is about as useful as my pointing out that it does work for my platform.
The reason it's not useful to you is because you didn't repro the issue but rather loaded it on a bunch of other browsers, so understandably you don't see how painfully obvious the problem is.
Working fine only on large screens is not working fine, even for the HTML4-era standards.
This is on Chrome on iOS.
I'll happily file a bug report. Anyone want to help me do so?