Ok, lets do this bit by bit.
The games look was simple but pleasing enough; gradients are used but sparingly and are not preset. This gives the game a nice minimalistic look. The character also has a nice glow and level-end messages look professional. However, this must be taken with a grain of salt. The character's jump animation is poor, some of the backgrounds lie on the bad side of the amateurish/minimal divide and some of the fonts are still in either _serif or some other kind of default that contrasts with the game's look.
This is where you need some serious practice. The entire game feels like a compilation of little bits of code taken directly from multiple tutorials; whether or not this is actually what happened is none of my concern. The collision detection is primitive to say the least (the character is in a constant state of minuscule bouncing when static, you should not be able to go through the side of a platform and you really ought to be able to pass through the bottom of a platform). You also need to work on your gravity; tweak the drop off point of the arial arc so that it actually looks like a curve of gravity easing and not a cliff.
Well, for one, the sound glitched out on me so there wasn't any, but even listening to the songs you used I know they don't fit with the game; credits song excluded. If you're ever planning on making another update to this -- search a bit harder for music that works.
Overall, 5/10, 3/5