Holy, that's a lot of awesome ideas.
First, the indication would have been awesome. I know the enemies appear a bit suddenly, and if they are stronger than you, you are pretty much done.
For the point you make with the mouse, that was something I realized while developing, but I just didn't have time. I am probably going to change it, so if you hover over the UI or want to place a block, I am going to deactivate shooting for that time.
Not seperating the resources would have been better, true. I don't know why I did that, now that I think about it. It would have also saved me some UI space, haha.
Thanks for the great feedback and playing my game; I really appreciate it.