I don't understand the way money is earned. I got 6 stars on every level including the "big boss" and still don't have enough to purchase all of the upgrades.
I don't see the point in adding more bubbles. Isn't it all just aesthetic except for the area where you can be hit???? Why would you want to give yourself a larger hitbox?
 "Heavens")
 "My Pet Protector 3")
 "Kamikaze Pigs")
 "Wentworth")
 "Super Villainy")
 "Rainbow: Forever")
 "Tyrant")
 "Electric Box 2")
 "Recordshop Tycoon")
 "Dynamic Systems 2")
 "Epic Battle Fantasy 3")
 "The tip book!")
 "Hop The Gap Again")
 "Gem Defender")
 "Lasers")
 "Custom Xbox Maker")
 "Age Of War 2")
 "Bubble Tanks Arenas")
In my book 100% difficulty means it's impossible... so 90% is pretty tough but still doable!