Fun concept and easy to understand. The initial screen is pretty chaotic tho. A lot of information and it took me a while to understand how to actually start the game, I though it was a bug or something, the start button with weird text formatting and no border was really hard to spot, might want to move that to a more natural location like bottom right of the screen and surrounded by a button or something. Also the game didn't seem to ever end ? Maybe make waves with a ramping difficulty in each new waves to have a feel of progression.
Fun idea.