What is UI CSS?
It's a set of UI components written entirely in CSS (Sass) and HTML (Jade).
Can I use it on my projects?
Yes, you can. But I do not recommend, as it's meant only for study purpose and it can have browser support issues.
Demo
UI CSS Tooltip
http://codepen.io/AndersonMamede/pen/wKJZzX
UI CSS Checkbox
http://codepen.io/AndersonMamede/pen/EVWJwP
UI CSS Radio
http://codepen.io/AndersonMamede/pen/YyZMrx
UI CSS Treeview
http://codepen.io/AndersonMamede/pen/ojWPmW