Sud comes from the creator of the popular Nord theme for the Gnome Shell, and is actually something like the “dark” version of it.
This theme is both elegant and beautiful, and although some elements like the search bar on the activities overview seem to be darker than they should, Sud retains normal usability value thanks to its precision in design.
As i said, the darkness of some elements is the only thing that may cause your eyes to glitter after a while, but this is also exactly the source from where the elegance of this theme stems.
The contrasted white colored info bubbles, the mildly transparent dark panel and light grey selection bars improve greatly the everyday usage situation experience.
A very nice theme in general, that works well, looks nice and fits my taste of elegance. I plan to keep using this one for some time :)
It is suggested that you combine this theme with the Lato font family that will provide a more stylish result using open source content.