Using SASS in Bootstrap Drupal theme

As of this writing, Bootstrap Drupal theme only supports LESS. This tutorial will show how to create bootstrap sub-theme supporting SASS and use Grunt to manage our workflow effectively. My operating system is Windows. Therefore, the shell commands, output, etc. that will be shown here are for Windows.

Compile imported regular CSS file in SCSS file to SASS @import rule

With SASS and Compass, all the imported SCSS and SASS files can be compressed and merged into a single CSS output file. What about the regular CSS files? According to this documentation all files with .css extension, it will be compiled to a CSS @import rule.

For example, if style.scss contains:

@import "../../bower_components/animate.css/animate.css";

... it will be compiled to: