NewFolder is a private design system that you're free to use, if you like, though it was designed for my own personal projects. It's specifically meant to be used with documentation sites, wiki-style sites, blogs, and other text-heavy websites. It's based on SCSS, mostly, and it's meant to be easily dropped in and integrated with any CMS you need.
The base framework is layout-agnostic — focusing mostly on content styles — with some navigation patterns and a few icons thrown in. That is to say, you'll need to create full layout and page designs yourself. I recommend CSS Grid and Flexbox.
You can see it live right here (you're looking at the NewFolder for Typemill theme), as well as on my personal website. It's intended to be minimalist, responsive, easy to customize, and extremely flexible. Here's a quick overview of the major features on offer, and you can have a look through all of the docs pages to see what NewFolder can do.