metamask-extension/ui/app/css/index.scss

/*
  MetaMask design system imports
  The variables declared here should take precedence.
  They are included first because they will be used to replace bad variable names in itcss
  prior to it being fully removed from the system.
*/
@import './reset.scss';
@import './design-system/index';
@import './base-styles.scss';
@import '../components/app/app-components';
@import '../components/ui/ui-components';
@import '../pages/pages';

/*
  ITCSS

  http://www.creativebloq.com/web-design/manage-large-css-projects-itcss-101517528
  https://www.xfive.co/blog/itcss-scalable-maintainable-css-architecture/

  DEPRECATED: This CSS architecture is deprecated. The following imports will be removed
  overtime.
 */
@import './itcss/settings/index';
@import './itcss/tools/index';
@import './itcss/components/index';

/*
  Third Party Library Styles
*/
@import '../../../node_modules/react-tippy/dist/tippy';