Not enough recharge? Upgrade recharge. Too easy to die? Upgrade health/armor. Tada! Final boss is too easy. Periodic explosions hitting both its missiles and the boss take it out in no time. Max Power takes it out in seconds.
Even with having 'Unlimited' space, I start to lag 1000 enemies into Insane. I beat it, sure, but impossible is impossible, not extremely difficult. Make it so the other 90% of people who play this can even attempt to get the impossible badge, please.