I love this asset pack from Kenney, I used it myself in a game. The polish is great. The sound, the atmosphere, the juiciness and the way the tall grass moves as you go through are all top notch. The concept of turning the pixies into weapons and shields is brilliant (close to how I approached the theme).
Sprinting proved to be pretty OP as I could just run past enemies. I suggest putting in gates that only unlock once you eliminate them (or at least a few). And I had the same problem as Pavel with the boss, when I started using the gun I took our one part of the boss and the game crashed.
Overall really good job, I enjoyed this one a lot.