It's not bad, and it is fun, but I don't really like the randomized towers. It takes away the strategic aspect of tower defense games. But I'm not that good at TD so what do I know? One other note is that it's a little hard to understand what is available, the first time I got to choose what kind of wave I would face I didn't even realize that's what it was and thought it was like an upgrade with a cost, and I thought the bright red outline meant it was the only option I could afford.
Edit: some people like hard games and sometimes I do to, but it is very frustrating when I have two bats and a skull with a fungi tower and still barely kill any enemies.
Second Edit: Got good more or less. After playing for a while I found there actually is a lot of strategy. I realized it's all about choosing the right enemies and selling the right towers and now I've gotten a lot farther.