This is my custom css, it supports firefox themes, works on all operating systems, comes with a completely reworked devtools menu. The github link is in the comments
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https://www.youtube.com/watch?v=_eJtw080JwQ
https://www.youtube.com/watch?v=_eJtw080JwQ
Thanks, and if you're intrested in a different look, you can look around the firefoxcss store: https://firefoxcss-store.github.io/
If you're intrested in that, there are some Ark themes in the store: https://firefoxcss-store.github.io/