Nice game, 4/5 , i would consider adding an upgrade screen between a lvl and another which like Acemarch said, makes the stars usefull, the upgrade should be permanant, like extra starting cash, reduces research point/cash cost of al towers by x%, in each lvl we get a free weak tower...etc. and these upgrades can be pgraded even more...etc. and also no bugs except for the negative money when upgrade all button i pushed...etc. other than that, your game rocks
A message to all : Light Bringer i currently sick, and does not seem to heal soon, however he is working on ltf3 very slowly though but he is doing the best he can, read the shouts on his profile :)
Shop still has a bug, i went to the shop , it wrote i had 0$ (i actually had more) and when i clicked on the helper upgrade icon,i bought it and i had 15$
I am looking forward to correct this.