I think overall it's a really nice game with a lot of potential. Honestly, I think the beginning is a little too hard. The difficulty should be more progressive.
The player is confronted to a new mechanic, he needs to try it in a safer environment. It could've been just a bottle of milk without any obstacle that can kill you. So you just test how it works.
At first when I've received the first bottle of milk I tried the jump mechanic and then I was punished when I've encountered the first obstacle since I needed to double jump.
Level Design is quite hard though, your mechanic is fun and the game has a lot of potential! It can only become better with more balancing :) Great work!