Looks nice; very bootstrap-y. With all the component libraries out there today, it'd be nice to know what's different about this one? What does this library solve that others don't.
Smooth UI is not better than other libraries like Material UI or Ant UI but the focus is different. Smooth UI put the focus on developer experience, extending a style is very simple. Also it exposes some classes, you don't have to learn any API to extend components, you can simply inspect components and use the classes!
Looks like the example uses that because it would otherwise be overridden by the variant=primary (which seems to be the default) so explicitly overriding that variant would probably be more intuitive and not require the !important hack.
This is a really good point... particularly with React Semantic UI [1] and Material UI [2] having tons of existing components, as well as pretty nice developer experiences.
FYI Grommet V2 has been in active development for a while and is now in beta. For styling, they’ve replaced SASS with styled components, which I think is a great move.
It's really nice to see a UI component library that is built on SC. I have multiple applications using React Semantic UI and it can sometimes be a pain to extend / compose its component's styles using SC (typically when working with child elements). Usually if you want to work with SC and vendor UI systems / components, you'll be working with CSS/SASS/LESS/Etc for the vendor components and SC for your own components. With a library like this, most of your components are now all SC (which has other benefits aside from just uniform style composition) :)
Edit: I think a big point that most non-frontend developers miss about these type of libraries is that they're designed to be extended, not necessarily used out of the box. Even if it looks identical to Bootstrap, the idea is to be able to have a nice base set of UI components that we can extend with SC -- the same way we'd extend our own internal components with SC.
Great work!