there is some strategy to it though, I usually use golf balls with the softball upgrade to make a wall, and then the main ball with the gun upgrade is a last resort if any sneak through. (got at least to wave 50 with this strategy)
even if you have the parachuting thing turned off. they'll just stop coming after a while, the trolley will still come. but there won't be a gourdlet dropped off.
does anyone think that the green boss is just a deadly box or something? It doesn't roar and attack instantly, but rather just sits there until you shoot it.
you can, at the bottom of the screen where you see your lives, there should be a bar that increases every time you kill an enemy, that's the level up bar.