Opencart 3. Scss Style Sources?

Question

css

I installed Opencart 3, I want to change some styles in the standard theme.
As far as I understand, SASS/SCSS is used in opencart 3. (in any case, there is a button that disables the SASS module, and there is also a class for compiling styles) I would like to use this feature.
But I couldn't find where the sources are. In this regard, I will formulate questions:

1) Where are the source codes, or where can I find them on the network (I did not find them in Google)?
2) When using the preprocessor, are the styles rebuilt every time or are they cached?

Answer 1

1) opencart sources ( styles )
2) compiled to css