Used as a template for Cinnamon-plugin: 0dyseus@CinnamonTweaks
Code for inversion shader: https://github.com/maiself/gnome-shell-extension-invert-color;
Original idea: gnome invert window extention; https://extensions.gnome.org/extension/1041/invert-window-color/
Coded from 2AM - 5AM, so don't expect too much, but it works