Flexi is a Mobile-first responsive layout in Drupal 8 Base theme and we have fully themed in Drupal Components like [ Blocks, Forms, Tabs, etc.],
Most flexible & user-friendly theme for backend and frontend.
INSTALLATION
1. Download Flexi from https://www.drupal.org/project/Flexi/
2. Unpack the downloaded file, take the entire Flexi and place it in your
Drupal installation under /themes. (Additional installation folders
can be used; see https://www.drupal.org/docs/8/extending-drupal-8/installing-themes
for more information.)
3. Log in as an administrator on your Drupal 8 site and go to the Appearance page
at admin/appearance. You will see the Flexi listed under the Disabled
Themes heading. You can select Flexi is administration theme and default theme.
4. Now build your own sub-theme set Flexi as the Base Theme.
Responsive
Font Awesome
Font Awesome is used for icons.
http://fontawesome.io/
SASS
Flexi is a Drupal theme & it can be compiled using CSS Preprocessor SASS.
You must be setup SASS first in your project. Read more in http://sass-lang.com/