Ohh! I really liked this one!!!
I have some feedback you could take into consideration in your next builds, if you want:
1.Screenshake, flashes and more particles! It would really enhance the game "feel"
2.Make the shooting towers visually distinguishable depending on their hp and shooting patern
3.Make the spawning of the enemies and spawning of the bits different (Some times I saw a tower spawning and went for it thinking it was a bit)
4.Make lower hp towers spawn more at the begging and less as the highscore increases
5.Add some pitch variety to the "glink" sound when collecting bits so that it doesn't get repetitive
All in all, those are just some minor tweakings you could do. Overall I really enjoyed the game!!!
Good Luck!
P.S.: the walking animation is slick!!!