A basic overlay / explanation of the controls would be helpful; I spent a few minutes not realizing I could zoom in with the mouse and everything was so *tiny*.
Not being able to unassign dorfs from their posts made me sad. :( Let me resource manage my people! Pretty pretty please.
As for an endgame, maybe building up something on the surface? A great statue to dorfs perhaps, or tribute to the local dragon council...
I really liked the minimal graphic design. watching the minecarts zoom back and forth and the little smeltery animations are satisfying. It'd be cool if some of the library upgrades resulted in graphical additions to the mine, maybe brewery stuff or a pub, underground gardens, stuff like that.
Looking forward to seeing what you'll do with this after the jam!