There are lots of things i can think of that you could add to it(like: creep abilities such as slow hp regeneration, towers that have different types of attacks eg fire, earth, peircing and creep armor that is resistant to some sorts, user uploadable artwork for towers ect, more tower abilities like burn-damage over time stun- stops moving for a short amount of time ect) and some bug fixes(when towers are sized 40x40 they can be placed on the path, sometimes towers can be placed on each other ect) but great game good improvement over the other two TD makers,, Keep up the good work!!!!
Next time the creator adds a change it should be to allow diff types of towers eg frost tower(slow enamies a bit for a while) and allow the user to change the attack speed of the towers all of this and I would rate it 5/5.