Nice use of the asset pack for a tower defense game! I liked that you could compose towers from different parts, rather than it just being a traditional shopping menu.
I will admit that the controls weren't immediately clear. I finally figured out that I had to click a spot first, then drag a platform to that spot, then drag a gun on top of it. I thought I should be able to skip the first step. If you keep working on this, maybe you could have the instruction showing while I am able to place objects. Sort of like a tutorial scene?
Nice job!