had to check this out as soon as i had the energy because it was strikingly similar in concept to my own entry. it's cute! i like the music a lot. there doesn't seem to be a reason to use the lower cash towers once you can afford the higher value ones, though.
also, there's a bug where if you exit to menu and start a new run, the enemy move speed won't be reset. not a huge deal, you can reload the page/restart the program to fix it, but it's worth noting.