Feels like this game wouldn't need to exceed 20MB... have you tried compressing the audio? If that doesn't work, how about cutting out audio for the demo, or using a shorter, looping version? I just can't imagine the graphical assets or code take that much space, though maybe it does have a huuuge amount of levels! I liked the game, the clever title, the progressive learning curve where it almost seems like a kids game at first, then quickly moves onto a notion of I-wonder-if-the-math-is-going-to-get-over-my-head. Controls are simple, graphics smooth, overall fun to play.
One thing that's a bit misleading btw is how you 'die' if you fall off the screen, yet end each level by falling through an answer of choice. If the image froze or faded before you see yourself falling out of the picture, it'd give the impression you aren't just falling off but actually warping to the next level. Or, you could have a falling motion at the start of each level, so it seems like you fell down from the former one. Anyway, just a minor detail, overall it's all good!
-cd-