Sure. Firstly, the player doesn't seem to accelerate unless it's touching the ground. That makes the character almost uncontrollable after leaving the ground. Also that makes jumping on higher platforms very tricky because there is not enough velocity to make the jump. Secondly, the jump height is too small. I understand there is a double jump, but even the first obstacle in the game is frustrating to overcome. Also, I am not sure if this was intended, but it's possible to wall climb, making some platforming sections meaningless (like the the small platforms on level 9).
I would suggest some improvements: make the player accelerate faster both on ground and air, increase the gravity and make the character jump higher. That way the player should navigate quicker and with confidence through the level. Maybe add some dust particles when the player touches the ground.
As I stated before, It's a nice game, and I hope you can find this feedback useful in some way.