I've always been into tower defense games, this is a simple one but all the core mechanics work, so good job :) first thing I would add is some sort of "game over" screen, I didn't realize I had lost for a second :D
LOL yeah, I ran short on time and a lot of the stuff that I wanted to add- I wasn't able to unfortunately. But hey, I made the type of game I've wanted to make for a while.