Yay for Unreal!
I really like the mix of styles, 2d sprites + somewhat 3d background. The gameplay itself was quite enjoyable once I got a hang of it. I just wish there were some kind of win-states and maybe transitions to different levels instead of it just being a high score chase (or maybe I just didn't score high enough to progress? but I think there is only failstate if towers stand for too long).
A neat concept of reverse tower defense but with an additional twist, I absolutely loved that it was not just a simple "you are the enemies" take on the theme. I could see some possibility to develop this idea further if You wish to in the future, as it definetely has potential.