1. I feel like there should be a circle that appears when trying to place towers or when you select one, that way the players knows the range of a given tower.
2. I think if you put some visual label on towers and enemies that signify if its ground/air based would be good.
3. I like the overall difficulty of the game
4. I did not notice the health of the towers. Is it possible to show a health bar for the towers?
I really liked the tracking and animations for the sniper towers!