Maintainable CSS with visual regression testing and functional CSS

<!--HTML-->Maintaining CSS is hard. Once your CSS files grows big, they become full of duplicated rules and unused code. What can we do to solve this problem? In this talk I will describe two concepts that can help us writing maintainable CSS: * Visual regression tests that can help us refactor our CSS with confidence * Functional CSS - a different way of writing CSS that can help us produce more maintainable code in the long term