i found it very easy to use. at first i looked at the menu and wondered for a while, but then i read it, found similar setting as my golden and warm days with f.lux

brightness 0, contrast 10% and sepia 50%! perfect! many cheers!

5🌸 ⭐ 🌞

If in Google Docs, it inverts imaged no matter what settings you activate. Otherwise, works pretty well!