Bulma

Bulma is a free class-based framework for CSS. It allows developers to implement CSS on web pages more efficiently than plain CSS. First released in 2016, Bulma has gained traction among front-end developers, enough to compete with other well-known CSS frameworks like Bootstrap.

Bulma is built on Flexbox, a CSS layout model that automatically adjusts the width of a page element based on the width of its container. Flexbox requires developers to write both HTML and CSS to create elements that adhere to this model. With Bulma, Flexbox behavior and most other things can be handled with HTML classes.