Great game! I wasn't able to finish it due to some of the jumps being a bit too difficult for me. Specifically the jump where you have to stand on the VERY edge of a platform to jump to the platform above you. I simply could not do it. Those jumps should be made much easier. Level 1 was also pretty difficult to be level 1. I would give much more time to the player.
My only other feedback would be to add a sound effect when picking up gems and you should really remove having to press the F button to proceed. Simply colliding with the guy when you have all the gems should instantly end the level.
I hope you find this feedback helpful! Keep up the great work!