The music was amazing. I absolutely loved the 8 bit graphics too. This is a semi-decent platformer, and I feel like a lot of people are underrating it.
That said, there are issues with the game, and they all seem to stem from the design choices. Why bother putting a square planet on every level if I have to fall to the edge and wait for a cut scene every time? Why can't I jump around the planet freely? If you are going to steal enemies from other games, don't steal Goomba's when the mario universe has Spiny's. Having to click continue and again on the next level #, when it could have automatically progressed me from the door of the last one was annoying. For that matter, why did I have to press x at doors? That's what bothered me, but read the other comments because they will cover more opportunities.
Despite all that, I actually really enjoyed the game, so what ended up bothering me most was that it never really got HARD (A medal after each level was overkill!). Overall, the game felt like a really solid platformer buried under a few poor design choices.