Great job! I am a fan of tower defense and definitely enjoyed being the tower offense this time mwahaha, what I think would need to improve is the UI, maybe place the money at the top, it took me a couple of seconds to find out it was at the bottom left, I think we are all used to see the resources available at the top lol
What I loved: the whole concept of buying enemies based on money, LIVE, that kept me engaged picking up coins and trying to see which enemies would be the best option at the moment :) loved it!