css3-mediaqueries-js : make CSS3 Media Queries work in all browsers (JavaScript library)
emotion : emotion is a high performance, lightweight css-in-js library that supports both string and object based styles.
darken : Easy control over your dark mode in a web environment
css.gg : Minimalistic icon library Designed by code, Customizable & Retina-Ready icons — built 100% in pure CSS. Easy integration: Embed, NPM & API
Styletron : Styletron is a universal CSS-in-JS engine built from the ground up for high-performance.
A modern, HTML5-ready alternative to CSS resets
Normalize.css makes browsers render all elements more consistently and in line with modern standards. It precisely targets only the styles that need normalizing.