Like this isn't too difficult until you get the rocket. you have a rocket force, but when the player moves midair instead of adding them you switch to the player movement only and that makes it very difficult and not fun to use. The other complaint is that the game is too bright, it actually hurts my eyes a bit, you should try to use a mario color pallet instead to get the same effect but nicer to look at.
You levels are well designed and the assets do look nice, it would be a really nice platformer if you fixed the above. I like the concept of rocket jumping, so if you execute it well this could be a great game.
If you want an example of good 2d rocket jumping, this is the perfect one: https://www.kongregate.com/games/bitwrit/rocketjump