Tweaking Casper theme - thin navbar

I quite like Casper theme and I’m trying to mod it a bit.

I’m not too fond about thick logo and navbar on the main page (index.hbs) - I’d love to change it to be identical as on the post page / static page. Thin bar with accent color, small logo and navigation. How would you approach it?
I’ve been fiddling with it without much success as there’s some more funky css things going in there I can’t wrap my head around. From what I see there’s so separate header.hbs and the header is set in default.hbs . I don’t get how it’s being displayed/constructed differently on index pages and on other pages.

default.hbs is the main template. If you look through the default.hbs file, you should see a section of code that says:

        {{!-- All other templates get inserted here, index.hbs, post.hbs, etc --}}

Here are some links that should help you:

Thx for the links Donald. As mentioned in my post I know that header in Casper is set in default.hbs.
The issue is I can’t figure out what is going on there. I’m no css expert - I can do simple things and tweak here and there.
I’ve managed to carve out the part I don’t want (huge site logo area). But the problem is that I don’t see @site.logo on main site ( / ). On subpages it’s there.
I can’t wrap my head around how it is set up that it works differently when accessing / in comparison to everywhere else.
As soon as I apply gh-head-logo css class the @site.logo disappears from / . In the worst case scenario I’ll create my own class but I’d prefer to understand what’s going on and keep as much of the original styling as possible.