I have several CSS files all being used in a large application; most are legacy, with one "main" css file that is the most current. This setup came about after a rebranding, and instead of redoing all of the CSS, we simply added a new CSS file that would override the rules from the legacy files.

So now, I'd like to distill all of this CSS (1000's of lines) into 1 file. NOTE: I don't want to simply combine the files (as in copy/pasting them all into 1 file); I need an application to semi-intelligently look at the rules, reduce them down to only the effective rules (after inheritance), but I can't find anything like that.

Example; given:

/* legacy.css */ .foo { color: red; margin: 5px; }

..and:

/* current.css */ .foo { margin: 10px; }

I need a tool to output:

/* result.css */ .foo { color: red; margin: 10px; }

Does such an application exist?