Cool! The game is very complete and juicy! Almost everything felt so good in this game!
Because I see a lot of effort, I want to share some critism.
I didn't understand the point of Blue/Red bullets. I know there is an alarm sound that remembers to swap, but I couldn't see the difference between using one or the other. Also, the upgrades menu became a bit broken, so I couldn't click on other tower upgrades but the blue one (and I only had two). Also, it is hard to see the enemies that come from the background.
I see a lot of effort and love behind this game. If it is a prototype of somethinh bigger, go for it!