Inheritance issue with Quark - header 'animation' broken

Hello, I'm a bit of a newbie to this, so apologies if I've completely missed something.

I wanted to set up inheritance from quark, so per https://learn.getgrav.org/themes/customization I made a new folder for 'pequark' and created the files and folders mentioned, up to the section on SCSS as I don't plan to change that. I then created an images folder with my logo SVG, and made a copy of the folder structure down to base.html.twig which referenced the logo file in the two places it was mentioned.

The theme cosmetically appears to work, but the top header no longer resizes upon scroll. I tried adding the header-animated class, but to no avail (I may have misunderstood the usage of that class?).

Ideas on how I can restore the resizing header?

Thanks in advance for the help, and Grav - it's been really interesting.

As an update, I couldnt seem to get much further - Quark's structure seems sufficiently different from the examples given for Antimatter that my inexperience can't seem to bridge (such as how do I run SCSS, and from where?), so I'll give it a break and just keep my hacks on Quark which seem to work, and avoid theme updates to it until I get chance to revisit it.

Don't know if you already found this, but the quickest solution I found was to copy the contents of the quark.yaml file onto the end of mytheme.yaml

I'm guessing that the things most needed are the header-fixed: true and the header-animated: true

HTH