Thanks for the feedback regarding the difficulty.
I should add a tutorial or perhaps easier first level as well as perhaps a different way of balancing things.
The first level can be beaten by using only 3 attack structures, roughly half of the starting resources and no other structures. I thought the game might be too easy but it must be because I built it from the ground up. I'll have to consider rework and a different sort of balancing to allow a wider audience to enjoy it.