P.S. Has anyone made it past 5-1? What's your secret?
I almost always die in 2-2 or 2-3... Run out of time, and can't take out all of the toxic ones. Made it to 2-4 once, but that's mostly luck by getting a powerful extra real early on. I never run out of health, but always run out of time later on.
(The best extra to get is the black spiked ball one just when you run out of time, since you become invulnerable to the toxic bubbles in that form)
(As a side note, My 2 year old son has cleared level 1-1 several times, and 1-2 once as well)