The |direction_css filter is applied to a CSS stylesheet and replaces any occurrences of left with right and of right with left [1].
Depending on the language of the environment [2], the filter therefore makes it possible to completely "invert" any such directional rules specified in a CSS file.
This filter starts by searching for an already existing (inverted) file, and if it doesn’t find one, then creating one within the local/cache-css/ directory.
If the stylesheet includes other stylesheets located in the same (host) domain (using the @import url rule within the file), the filter will propagate its modifications down to the those nested files.