Everything is good except for the actual game play
The music and graphics are nice, but the actual game play is flawed. The controls are super stiff, which means that you have to press on the key very hard to get it to move. More responsive controls would be a major improvement. Also it would have been nice if you had included a health bar instead of you getting killed by everything.
In addition, there are too many enemies coming at you. Combined with the other issues, it is almost impossible to dodge all the enemies, rocks and the skin. Come to think of it, why does crashing into the skin hurt you? It should be SOLID instead of being possible to fly through so that it doesn't hurt you. One last issue: going off screen kills you. Why does that kill you? Other games don't do that. There should be an invisible shield that prevents the player from going off screen.
All of this results in the game being rather difficult. In fact, I still haven't beaten the first boss of the game because of the problems described, in addition to it having so much health that your weapon is nearly useless even with the maximum upgrade. If the first level is that hard I can't even imagine how hard the rest of the game must be if you manage to get past that boss.
Come to think of it, these problems are almost identical to the ones the game "Silver Surfer" on the NES had. (watch a review of that game or play it and you'll understand immediately what I mean by that) I hope you look at this review and use the feedback to make a better game.