adapta-gtk-theme (Gtk+ theme)

adapta-gtk-theme is an adaptive Gtk+ theme based on Material Design
Guidelines.

For OpenBox users:

Compton is the famous stand-alone compositor that works well with the
Openbox window-manager. This package provides the recommended
configuration file compton.conf in the Adapta/openbox-3 directory.

Just copy this file into your ~/.config folder and restart compton.

To properly work, this suggests the optional dependencies:
ttf-noto, ttf-roboto.