Hey, I just tried out your game, it's already pretty good!
Some tips: You have probably already thought about this, but I would make the fog-of-war tiles black instead of white. It's a little easier on the eyes and looks a lot better in my opinion.
Also, I think the game will look a lot better if you add lighting/shadows to it, no shadows makes the game look a little flat.
Another change that might help is adding little grass patches to the bottom of the structures, minor stuff like this can make the game way prettier.
And from a gameplay perspective, when placing buildings, adding workers to it everytime can become tedious. So maybe when building something, have it automatically assign some workers if any available?
Lastly, the UI is good for now, but you might want to change that at a later stage as well. I got lost a couple times and the development/upgrade menu is a little overwhelming. Maybe some clever colorcoding can fix it.
But I have to say, I'm impressed with the level of depth the game already has, I use Unity myself and I can tell that this costs a lot of work to implement and have it function properly. Anyway, keep up the good work, looking forward to seeing where this project leads!