while not the seriously bad, I have a few problems with this.
some of the bugs I encountered: occasionally I had my character duplicated. while you pointed it out in the author comments, it happened to me when I simply spawned in the second level, not from an enemy. it stopped after I jumped a couple times. another bug that I encountered was at level 5. i was on the second non-moving platform, when i glitched through the floor. then, when I spawned I fell through the floor. and again, again, again, falling faster each time, until I couldn't even see my character. I couldn't continue without restarting.
now, I want to know: is this just a test, or is this going to be a proper game you're going to submit? because, as a test of your capabilities, it's pretty decent. but, as a proper game, it's not very good. the backgrounds and platforms are bland, it's generic and basic platformers like this have been done to death. if this is going to become a proper game, it's bad. but, if it's just something for you to hone your skills, show what you are capable of, it's good. at any rate, this review is waay to long, so I'll wrap this up. good effort, I've decided to favourite you, because I think you have great potential. I look forward to your future projects!