It has 4 presets that can be configured per domain.
I’ve added by hand rules to fix inverted images on some popular websites. YouTube is a pain to maintain, they keep changing their css every couple of months.
The code is simple enough to review even for someone not familiar with JS. And you can download it and load it as a local extension if you’re worried about the permission.
I’ve only tested it under Linux, I don’t use anything else. But some users tell me it works under Windows too.