Its very similar to this, differences I see are:
It uses C/Lua, not ruby, so the cool kids probably wont use it.
Its compiled, so no interpreter needs to be installed.
Its very fast so it can be run as a cgi script, either for just development (avoiding the compile annoyance), or live (as its site uses now), or run from the command line to avoid the compile overhead in production.
You can add functions written in lua and compile them into the executable.
The variables are defined in a separate file, so your editor won't freak out in css mode.
When I introduced it got on smashing magazines best of whatever, http://www.smashingmagazine.com/2007/08/14/best-of-july-2007...
I had a lot of css hipsters hating on me... a lot. They despised it.
Their arguments were like "you don't need variables in css, you have to use the cascade!"
Something like
.my_colored_div, .my_other_colored_div { background-color:red }
... then way further down...
.my_colored_div { width: 100px} .my_other_colored_div { width: 200px}
So instead of defining something once, (a variable), you should define something (dom element) in multiple places.
I'm sure its obvious to you guys that defining something in multiple places like that would end up a big mess. So it didn't bother me so much being criticised by a group of developers who probably haven't done more complicated coding than a few pages of php.
Anyway, I'm not promoting moonfall, I honestly don't know if anybody is even using it, I never did, (although somebody ported it to a perl module), what I want to say is ever since that project that motivated me to develop moonfall, I haven't needed it, because the way I approach css has changed for the better.
I have a few simple rules.
1. Avoid using css, it relatively sucks. Try to let the html do what it wants. The more css you have, the more you will be fighting the browsers.
2. If you need variables in your css, you are probably making a big mess that you will regret.
3. If you have a web page that needs a lot of css, its too busy, or looks too much like a desktop application.
4. Only put global styles in the main css file.
4. My most controversial rule, one that has helped me the most but will probably bring on the hating... If a style only needs to be used in one place, or you cannot come up with a good name for it, don't put it in the css file, put it in the style tag attribute in the html style="blah:blahpx". Trust me, try it.