You should be able to spend prestiege points BEFORE prestieging.
For instance
"Gain 5 prestiege"
"prestieges"
"unlocks "Start with 7 more Generator II"
now I have to prestiege again, to even get the bonus.
I dont know about everyone else, but I found level 21 pretty straight forward;
the way you beat it is that you tke out the outermost spheres, then work your way to spheres around those.
Also dont be afraid to reactivate spheres, to get a sphere behind them, you can just shoot them again once they've moved a bit.
if ppl dont get what i mean, what i mean is basically, use all your slots on flags, when you either dont have enough money to upgrade your ship or to buy a flag, exchange the weakest flag (the white flag) against the most expensive cannon you can get
Heres a great tip to complete the game:
just keep switching beewteen buying flag and ship upgrade, when you are at the 3rd, if you cant get 4k money in time, sell the cheapest flag in exchange of the 4th flag, on the 4th ship, sell thew cheapest flag in exchange of the 4th cannon, then once you get the 5th ship, you should have all the 4 flags, including the 4th cannon, then the 3rd boss will take like less than 3 mins
i got 37 trophies by just maxing out fire rate and spread and standling i got Terminator,
High score, Level climber and evasion expert on platinium by just upgrade fire rate and spread to max its amazing
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