Sometimes the controls were a little too slippery, sometimes the double jump didn't work. This sometimes wonky gameplay together with a save point only happening at every 5 levels (meaning redoing a lot of the same because you messed up just one part at the late levels) made me want to stop playing before getting to the end.
I liked what you were going for with the story and I liked that the friendly tutorial flames were from your friend, but there could have been more dialogue through those flames to establish and develop the characters and their personality. The info dump happening after level 9 wasn't the best way to convey your narrative. Progressing it gradually after each level (and maybe even tying it with what happens in the levels) would feel better.
I liked the music, the art was fine.