Make it so that the longer you hold down the jump button, the higher you jump. The current system of one press = one jump of uniform size has killed me a few times...
Little things like the bricks moving when switching between the shop and level select screens make it apparent that this game didn't receive the effort it deserved. It's a really fun concept, so I really wish you'd just give it that last 10% to make it seem polished.
I like the concept, but the background on the hard/impossible levels makes it hard to see the ball. Also, there is nothing hard/impossible about the hard/impossible levels (other than the retina-melting background).
 "This is the Only Level 3"){kind=icon}
 "Sandbox Hero"){kind=icon}
 "Symbiosis"){kind=icon}
 "Attack of the Heavenly Bats"){kind=icon}
 "Bloons Super Monkey"){kind=icon}
 "Vertical Drop Heroes"){kind=icon}
 "Nightmare Runner"){kind=icon}
 "Chickaboom"){kind=icon}
 "Unlucky Robber"){kind=icon}
 "Holons"){kind=icon}
 "You Create the Next Level"){kind=icon}
 "Meat Boy"){kind=icon}
 ":the game:"){kind=icon}
 "N3wton"){kind=icon}
 "5 Differences"){kind=icon}
 "Factory Balls 2"){kind=icon}
 "Vivirion"){kind=icon}
 "Wilt: Last Blossom"){kind=icon}
 "Breakbar RPG"){kind=icon}