Arc Maia Theme
Arc is a flat theme with transparent elements for GTK 3, GTK 2 and GNOME Shell which supports GTK 3 and GTK 2 based desktop environments like GNOME, Unity, Pantheon, Xfce, MATE, Cinnamon (>=3.4), Budgie Desktop (10.4 for GTK+3.22) etc.
The NicoHood/arc-theme repository is a fork of the horst3180/arc-theme repository which as been umaintained since March 2017. Its aim is to continue the maintenance of arc-theme. The two maintainers are the Arch-Linux and Debian & Ubuntu packaging maintainers.