Really interesting take on the tower defense genre!
Never seen a version of a tower defense game where you can only select one tower at a time. Honestly this game was really hard for me, I'm not sure why but I loved it. I just wanted to practice and practice and get better and better!
My only criticism would be to maybe add some feedback to the player when they use a turret that's strong or weak against a certain enemy. Such as a particle effect or a sound that would help the player know they are doing something wrong.
All around though a really cool game! :D
Great job chief!