Escala is frontend framework designed for medium to large sized web applications following this convention similar, but more pleasant to write, to BEM and written in SASS. Escala is based on flexbox and dual styles - separated styles for mobile (small viewports) and for desktop (large viewports). This doesn't mean Escala is not responsive.
Escala is available as the escala package on npm.
Add it to your projects with Yarn:
yarn add escala
npm install --save escala