woo godot
did you use v3.x or v4.x?
also, you can remove the gray outline around buttons that appears after you click them by going under Theme Overrides -> Styles, then setting Focus to StyleBoxEmpty
oh wait nvm you seem to have already done that for some it seems, just not all
It's made with v4.1.1, all gdscript, no C# or gdnative. You can find me in the Godot discord under @pignales if you want more details.
And yes, the UI definitely needs to be more consistent including setting focus to NONE on all buttons.