This is a fun TD game, but I feel like it is a bit lacking. I feel like it is a bit too basic perhaps and too traditional given the unique mechanics you are trying to introduce.
I would have loved to see the energy area you can build in to do something more.
Furthermore I would have loved to see buildings that would have played with the energy area more. For example basic tier 1 structures that are fully self sufficient, cheap, but very weak. And tier 3 structure that are incredibly powerful and specialized, but need a lot of support structures. Like an energy creating area to power the tier 3 turret. Or a buffing/upgrading building to buff the tier 3 turret.
This would give a very simple beginning, but feeds also into the long term planning of your base and making your mechanics more and more complicated.