Where can I find a manual for creating a theme on Opencart?

Question

Layout

I didn’t find it on YouTube (for some reason, there are mostly videos on opencart from people who don’t really rummage around, but only modules are sold a lot. Wordpress please, but opencart is not) and on the opencart forum (although maybe I just searched badly) so I think maybe here who will tell. I want to create a theme for the store and actually successfully put it on this same store. Please tell me the resources where it will be analyzed in as much detail as possible. Of course, I can take it and just start editing the default theme for myself, but I want it right from scratch. And there, after all, most likely there will be all sorts of pitfalls during layout related to the features of the engine. This, too, would like to be taken into account. And one more thing: what level (on a 10-point scale) of PHP and JS is needed to successfully put the theme on your store? I don’t plan to do anything pretentious, but I want it to be my own.

Answer 1

https://webdesign-master.ru/_lp/opencart/
www.allitebooks.in/opencart-theme-and-module-devel...

Answer 2

Webformyself had a course on this topic, pulling the layout on the second opencart is pretty well laid out.
If you want more, then only an independent study of the opencart source code, because there is NO off-line documentation from the developers from the word AT ALL