I used to mess around with addons like Stylize and such, but they worked very poorly. This addon is AMAZING!

GMail still fails, rachelbradleycomedy.com fails, and slows down loading pages sometimes a lot, you only need to manage the background when it's white or really bright/near white, or at least offer that option, the res of colors are mostly OK. For future upgrades: allow me to select on a webpage what colors I find it too bright, and to be reported back to you, to know what people want from this app, and allow my preferences to be stored on Google Drive or any another cloud for when I reinstall Windows please

Does darkens all websites I've visited except it reverts Firefox's new tab to light no matter when it's already light or dark.

Also, users with 4GB RAM on their computer would want more RAM because it eats up a lot gradually.