Would be almost perfect, except for one glaring issues that had caused me to switch to a different theme. There is insufficient contrast between the active tab and other tabs. If you have many tabs open it is difficult to determine which is the active tab to close it. This causes enough friction in working in Firefox that it became a regular annoyance. For me it is a basic requirement that the active tab should be clearly indicated in the tab bar. This otherwise excellent theme fails in this regard.

bien

edit color -select TAB
please.

hard to see active tab

Makes the menu bar practically invisible

Good, but really needs contrast on the selected tab background, I can't tell which tab is opened

Looks ok but the animation isn't very wide, so it's repeated 4 times across my screen when maximized.

On Linux, for some reason this theme makes all videos stutter and scrolling extremely sluggish. Once I changed, everything went back to great.

I very much like the theme. My only critique is that I don't like that I cannot see separators on the book marks bar. It just looks like an extra wide space. Fix and I'll change to 5*
EDIT: I don't see a bookmark specific component, perhaps its controlled by the "toolbar_vertical_separator"