So addicting! I have been playing this game for the past 2 hours. I finally finished all "tier 1" levels, but I still couldn't buy all the upgrades! I had only the attacks/minute and shield capacity left! and they were so close to being finished! If only the scaling wasn't kinda broken... I have never had such a strong love/hate relationship with a game before. I give it -10 out of 10^(i*pi/2).
If you make a mobile version of this game, with ads, you will be so rich.