I really liked this idea and think it's very original but it ended up being a little too passive and easy. I placed 3 turrets on the first few waves and they comfortably kept me at the right health for a very long time. When I eventually needed more towers I had a ridiculous amount of money which didn't feel very balanced. Then the win screen popped up very abruptly which caught me off guard. I think you could have done couple of pretty simple things to make the game feel a little better. First I would put a wave count somewhere so that the player knows it's not just an endless game and then the end wouldn't be so surprising. I would also either give the player much less money or just get rid of the money entirely as I don't think it contributed to the gameplay. Finally I think some simple animations when the turrets fire could have gone a long way to make the game a little more juicy. Overall, the game seems really well made and although I found it too easy, I think you made something really impressive and I love how different your take on the theme was.