Comment by provlem

There are many:

1. https://materializecss.com

2. https://getuikit.com/

3. https://semantic-ui.com/

4. https://foundation.zurb.com/

5. https://bulma.io/

6. http://getskeleton.com/

7. https://purecss.io/

8. https://groundworkcss.github.io/

9. https://cardinalcss.com/

10. https://github.com/powertoweb/powertocss

and many others