This website look pretty broken in my mobile browser.

Came here to say the same thing. Sorry to be “that guy” but it’s really hard for me to have any positive thoughts of a front-end web project when it’s website doesn’t work on mobile.

I don't know the motive for the site design, but I wonder if perhaps it wasn't coded for mobile because the app is not compatible with mobile devices but rather only Windows, Mac, and Linux.

https://github.com/marktext/marktext