This is great! I've bounced off a lot of city builders and RTS games in the past because they're so complicated, but this hits the spot. I agree with others that the text is too small, and playing in fullscreen the item / building popups are too far away - mouseover a building at the bottom, the text popup is near top left!! A small complaint, though! Also, night time seems to come too quickly, and is reeaally dark. For anyone else playing, remember you can zoom in and out with the mouse wheel.
I did well by adding a bunch of mines at the beginning to make sure I had the gold to keep building military buildings and units, which goes a long way to keeping you going when the big guys arrive.
Well done!