[SOLVED] GUI CSS questions

[MJR42]

Happy New Year, everyone! Here's hoping 2021 is a better year.

With the help of a few folks in this forum I've been able to figure out how to create my own version of the GUI for a small (5" 800x480) touchscreen to control my moOde box locally.

I've made a lot of progress using a Windows desktop for development, as outlined in "other\build\moOde development with gulp.odt", and now I'd like to try my moode.css on the actual RPi. I've got two questions I'm hoping that someone will help with:

1. Is there a simple way to transfer the moode.css file onto the RPi and replace the existing one, without having to create a full boot image?
   
   
2. As a first step to see whether the css would look different on another machine, I transferred the file to my laptop with an identical build environment. The display looks different, and I'm not sure why. It may be that the screen resolution changes something, but I'm using Chrome to set the screen size to 800x480 in both cases, and both the desktop and the laptop are 1920x1080. It looks like its related to font sizing somehow - I've set all the fonts I change using rem units, but the fonts are clearly a different size on the laptop. If anyone can suggest where/how I should be looking to identify the source of the difference, I'd appreciate it. I know this may be a noob CSS question, and if it is, some pointers to keywords/concepts so that I know what to read up on would be appreciated.