Enjoyable and Long lasting fun
This is an interesting an enjoyable spin on the rather ancient art of TD games.
I've never seen such a concept as controlling the waves of creatures rather than the towers, and I've got to say that it provides hours of enjoyment. I've not even seen past the 8th lvl, as I've been working towards powering up and gaining medals, yet I'm having fun with every moment. The difficulty curve is what you make of it, depending on how long you grind. But I can't really call this games grinding stage even that, due to the gold medals you're constantly working towards. And even though some of your power-ups seem weak (1% increases and such), they still provide a noticeable boost over time.
My only true qualm with this game is the inability to field upgrade. It's a common practice in TD games, and I can see why you'd scare away from it due to design changes and innovation. But at the same time I'd be an intriguing twist on mana usage. More of a suggestion than an actual problem, really.
Overall I enjoyed the project, and look forward to future iterations and innovations in the Villainous TD series.