In Brick River, you can work with your CSS using SASS. This allows you to reduce repetition and save time while coding because you can specify certain elements one time as opposed to throughout your entire CSS code. For instance, you may want to set a primary color and reference it throughout your code. With SASS and SCSS, you can easily define these sorts of variables.
SASS outputs both a minified version and a full version of the CSS. You can specify an output directory for SASS compiling. This helps for Bootstrap themes where the .scss file is in a different directory than the CSS files.
Here's a screenshot of how you can set the directory for the compiled CSS file. You click the "three dots" button to the right of the "compile" button to specify. It will then remember the location and always save it there.