An oldschoold platformer is always a cool thing, but this one need a bit more polish. The controls were a bit "floaty"- the character falls very slowly after a jump. Also- it's a bit difficult to say what elements are a part of a background and what is a platform you can jump on.
I see this was your first jam entry! Congrats on finishing your first jam. Keep making games and learning, and soon you'll be creating great games!