I liked the game, definatly think this game could go places and would like to see it go there :)
few things i noticed:
Turrets were a bit pain to place as i was getting stopped by them all the time when trying to place a nice "lane", maybe remove collision for player or add a aim so you can strafe but place them to the side
Base should probably not allow player inside? i was able to place turrets inside base which seems to break pathfinding for me
Adding a path visually by either a line being rendered or in texture on ground
i liked that the player and turrets had HP and the ragdoll of the enemies.
would have been nice if there was a wave-counter and a bit more TD like on the spawning approach?
more turret types would have been awesome!