A better, more compact UI for Firefox

Proton is Firefox's new design, starting from Firefox 89. Photon is the old design of Firefox which was used until version 88.

Proton's overall feel is good, but there were a few things I didn't like and wanted to improve.
That's why this project was born, and Lepton to denote light theme layer.

Lepton's photon styled is preserve Photon's feeling while keep Original Lepton's strengths.

Firefox UI Fix GitHub page

I do not like the current Firefox user interface, because even with the compact' layout re-enabled in about:config, I find it just too bulky and wasteful of my screen real estate. I've been using the above Firefox user interface mod for ages now, and I can't imagine using Firefox without it. The GitHub pages and guides are a bit of a mess and difficult to follow due to the project consisting of several overlapping different styles, but I just use the script listed here, selecting the style 2" when running the script.

It won't be for everyone, but for me, it makes Firefox nice and compact, turning it into a mouse-first interface without trying to accommodate touch. This is also by far not the only project with this goal, so if you're using something else - feel free to list them.