I like the slingshot mechanic for the character, it adds a lot of difficulty to the game!
The music is also a good fit for the game.
Good job on this, its a fun game to play!
Edit: Looks like I forgot to paste the rest of what I had to say when reviewing! I know that this is meant to be difficult, but maybe consider ramping up the difficulty more slowly, frequent checkpoints or increasing the jump height? It may be too hard to begin with for new players