This was pretty fun tower defense game! I normally don't like these types of games because the genre normally has increasingly harder waves that you somehow have to keep up with by upgrading things optimally and such, but I liked this one because it breaks away from that mainstream method and just has fun with upgrading towers via what combinations you want/need. It would be interesting if you added an extra challenge indicator for beating maps without taking any damage. Took me a bit to figure out how the towers worked, but managed to make them work to my advantage, which is part of the fun you made :3
You did a "tower"iffic job!