Ok... I got an artifact called ragnarok, I used it and like 40 huge grey dragons appeared and my wall health became -136352...
I'm sorry, i had rated the game 4/5, but now I'm rating it 1/5.
good way to get money:
get a few upgrades in fiering speed, and bullet number (front) and maybe a couple in shield and let your ship do the 1st lvl... go do something else, then come back and put it again... and so on. : )
I understand that cannon and thrusters are premium, they gotta pay the bills, but mirroring and scaling are essential for a physics game... should be free.