Great work! I really like it, and the overlay menu is very sleek and nice as well. I do have a few gripes though:
The compound icons used to be larger width than the bars beside them, which I think was far nicer looking than having the icons be the same width as the bar. I presume it was just a stylistic choice you made between them, so it's your call.
I'm a little undecided on the reproduction meter being represented by the editor button. I can see why you'd want to do that because it allows to drop the bar entirely, but at the same time it does make the Editor button look a little strange, and I think there are several checkpoints in the reproduction meter's progress, that might not translate well into being visually represented in the editor button's fullness.
How is fossilize different from save?
Fun fact, you misspelled compounds in the compounds panel , but more importantly, is it necessary to have that panel titled "Compounds"? I ask because I'm undecided on the merits of that as well.
I do prefer the grey theme, but that's easily moddable so it doesn't affect the discussion on the interface itself. Anyways, it's looking good!
EDIT: Here are the checkpoints.