All the Design Framework Classes
UIkit is a lightweight and modular front-end framework for developing fast and powerful web interfaces. UIkit gives you a comprehensive collection of HTML, CSS, and JS components which is simple to use, easy to customize and extendable.
Zurb Foundation is a very popular alternative to the Bootstrap framework. Foundation is a family of responsive front-end frameworks that make it easy to design beautiful responsive websites, apps and emails.
CSS stylesheets can become hard to manage on large projects. LESS is a solution that developers use to make their CSS much more efficient. As many designers know, stylesheets can become complex on big sites. It can become a headache to manage hundreds or thousands of styles. LESS allows you to use plain CSS, but also add programming features such as variables, mixins, and functions.