There are various places where UI elements are not clearly obvious in what they can do and what they can't (no particular order):

• "Victory conditions" on the "Create your world" screen have no disabled state (see also them changing the world name)
• there are buttons that are not of the white kind, but flat and see-trough in a brown/sepia tone. these always look disabled to me, and should have a clearer indication of being a button (or just be the same as all the other buttons)
• the big circles with image in the middle are used for various things. I'm not saying that they all need to behave the same, but they should be made less similar (for example have a rugged or dotted surface when they're draggable, or light up differently for double clickable).
  
  • option button (in the choose faction screen)
    
  • option button that are added to a list when doubleclicked (choose opponent screen)
  • as an image that shows a value, but isn't clickable (on the topright of the main map screen )
    
  • as double clickable drag droppable things that can be selected (similar to OS files, found in the technology screen)
• the kingdom info tab selectors are only clickable on the round icon, but not on the text below them. I'd suggest to increase the clickable area to cover the whole column, just make sure to divide at the right place. that will increase the clickable area considerably, and makes missing the tab button very hard (especially if you extend the clickable area to the edge -> fitts law).
• on the technology screen, the topright information (ie. "Research Points: 0.05 / Turn") looks like a button to me, but isn't clickable.
  
• on the main map screen, there's a very tiny button for the technology tab, but none for all the other buttons, which are only accessible trough the "kingdom info" button. that button is probably not going to be left alone, but it also has no tooltip. I suggest to not make any button that isn't pure text (shows icon) witouth a tooltip.
• albeit being disabled, the fore-back choice buttons on the "create your world" screen have black text, unlike all other disabled buttons, which have a reduced/gray/see trough text