Interestingly, I found it a bit too *difficult*, compared to all the people saying it was too easy. I couldn't seem to take out the tower on the third stage before it killed me (repeatedly) and all my troops. But maybe that's on me. (The seemingly-identical tower on the second stage was no problem at all, weirdly)
I also couldn't figure out how to cast spells other than Death And Decay, which may have been part of the issue. Edit: Oh! It's right there in the instructions, C to change spells! That made things much easier. :D
All in all, though, I love the concept, and I liked the few levels I could get through.