Excellent
Took me only a few tries to realize the "ending" was a facade. I managed to beat all the bonus levels, the last one had me for a bit! I applaud you for making something a perfect blend of 'easy-breezy' and extremely difficult!
Music: The "Running out of Time!" noises were annoying to say the least, especially on the last few bonus levels where you're ALWAYS "running out of time" ;P But at least a mute option was uncluded and instructed. The music however was very appropriate in setting the tone and was just freakin awesome to listen to besides ;P
Graphics: Well, It's 8 bit anyways. But very fitting for an arcade-style platformer (and puzzler!).
Bugs: One minor but irrelevant - on the level where you pick up a ton of speed up arrows and one jump arrow, you end up running right through a couple of the speed arrows. But this doesn't hinder your ability to beat the level so whatever.
It was sweet and simple, I liked it. Too bad there weren't any high score records for total lives lost, fastest level times or fastest total game completion time.