There are a lot of problems with the improvement builder and imrpovements in general.
1) If you click outside the possible tiles, it builds the improvement anyways on a somewhat random tile. This has caused me to very often build an improvement on the wrong tile by accident. It would be more intuitive for the game to just ignore clicks outside the possible tiles. Also, it might be reasonable to consider making you click twice to place the improvement. It feels really sensitive and a bit flimsy when a single click is enough.
EDIT: One reason those misplacements happen is that you can open the city view while not centerd in the city, and when you try to click on a tile to build the improvement the screen snaps to the city center and registers the click at the wrong coordinates.
2) The tiles of available spots do not always appear. You have to zoom out and back in to get the game to draw the tiles sometimes.
3) Improvements that require a special tile (farm, mine, lumber mill) should be colored somehow differently in the building menu to distinguish them easier. It is annoying to scroll over each improvement to figure out which I can't build because I don't have resources and which I can't build because there just is not such tile around. I still want to see the special tile buildings in the menu, colored red or some such when I can't build them on the tile, to remind me that I have the techs ready.
4) It says that you need tech X to build on a special tile even after you have researched the required tech. In my opinion it should clearly point out that you can use this special tile when you have the tech ready. I don't want to have to remember by heart which techs I already have.
5) It's also a bit strange that once you place an improvement it keeps the building selected and lets you place another house. This should in my opinion happen only when doing something like shift-clicking. By default it should only place one building and close the menu.
6) It would be nice if buildings were arranged by tiers or by some other intuitive means, since there are clear levels on improvements. The best option would be to have multiple sort options, with tabs for different kind of buildings. Off the top of my head here's one option of sorting/grouping:
- Population buildings: All buildings that increase population cap or prestige
- Trade buildings: All buildings that relate to gildar production or trade
- Academic buildings: All buildings that increase spell points, research or magic ability
- Warfare & Exploration buildings: All buildings related to warfare and exploration (seafaring etc)
Those groups could very well overlap each other somewhat. If a building gives both gildars and prestige, make it appear in both trade an population tabs. Other ideas I can think of are sort by building cost, sort by related tech tier, sort by name and sort by AI's preferences in current situation.