Very minor suggestion:  allow resource tooltips to still pop-up once you open the build list for a city.

Currently, when in the overland map, you can hover the mouse pointer over resource tiles to get a tooltip popup.  Once you open the city build screen, those tooltips won't pop up anymore. 

I often find myself hovering over resources while in the city build screen, wondering "what type of mineral is that" or "what type of shard is that", exiting the city screen, hovering over to check the resource, then going back in to decide on a placement for a building.  It would smooth out the gameplay a tiny bit by allowing the tile tooltips to popup with the build list open.

As I said, minor suggestion.  These little 'quality-of-life' UI things do help make the game more intuitive, though.  I've played the game for dozens of hours, but I still don't know at a glance what all the resources look like, and they still sometimes blend into the background - maintaining the accessibility of the tooltip would help.