Working with SCSS
Working with SCSS makes life much easier. We used it to write the design for Circular and we have used the following structure. The styling for each page is created compiling _base.scss (which are properties used in all pages), _responsive.scss (media queries used for all pages) and the specific files for that page: _components.scss (for things like buttons, forms, etc), _sections.scss (for big parts of the page) and _responsive.scss (for media queries).
If you want to overwrite the styling, you can create your own partial and add it to the theme_x.scss in order to be compiled with the rest.
We recommend you to create make your one own SCSS/CSS and JS files and add them to your page, so whenever you update the Circular theme in your project your code will not get broken.