Really cool mechanics, reminds me of a game I used to love back in the day with a similar node generation/capturing system.
Two critiques: Right-clicking the tower seemed to be very unreliable for pulling up the options on changing its mode. It would pop up several seconds later, or sometimes not at all.
And I would just absolutely love a "restart level" button. I ended up struggling with the second level too much and felt like the kind of start you get in that level is so crucial to how the rest of it plays out.
But great concept, and awesome job overall!