POS-Server/app/assets/stylesheets/main.scss

// "bootstrap-sprockets" must be imported before "bootstrap" and "bootstrap/variables"
@import "bootstrap-sprockets";
@import "bootstrap";

/* for bootstrap3 */
@import "bootstrap3-switch";
@import 'bootstrap-datetimepicker';

@import "simple-line-icons";

@import "font-awesome-sprockets";
@import "font-awesome";