EDIT: I should emphasize I'm particularly interested in experiences of using a tool (such as those listed above (in the absence of any better ones)) to convert a large CSS code base towards using a CSS preprocessor such as SASS or LESS. Or if any other ways (other than the tools listed) to ... More on stackoverflow.com

I'll try to give a simpler explanation, since kevan pointed out that menno's was a little high-level. SASS and LESS are just like CSS except with lots of shortcuts to write things in a much shorter way that you would with just CSS. The simplest example is using a variable. You can write "$brand_color: #FF0000" at the top of your SASS file, and then later on use $brand_color exactly like you would use the hex color like #FF0000. This is most useful when you use it in several places: then if your client decides his brand color is now #00FF00, you just need to change "$brand_color: #FF0000" to "$brand_color: #00FF00" once and that's it. Otherwise you would have to track down every place you used the brand colour and change them individually. You can set more complicated things called mixins too. A common example is to define a mixin called button, which you would use whenever you want to define a button. Mixins are very powerful because they can be modified by parameters. This means that if you realise that the CSS you wrote for two different buttons is identitical apart from some widths, because one button is bigger than the other, you could write a mixin that takes this number as an argument, and then you would not need to repeat yourself. Nesting is really nice because it means you write less. It's hard to explain, just look at the example on the SASS homepage . Because these are all "shorthands" for longer CSS, you need to first turn your SASS file into an actual CSS file, which just consists of expanding your SASS shortcuts into real CSS. For example whenever it encounters @text_color, it replaces it with #FF0000. This is called the compilation step; it is a program on your computer that you need to run, which outputs your CSS file. More on reddit.com

Try removing the / in front of src More on reddit.com

Hey everyone, I wanted all styles to a component to be wrapped in one place. I created a mixin to do that even when class is added on the most outer… More on reddit.com