This was really fun to play, and I feel it has a lot of potential. The controls are really solid, and very enjoyable after finding the heart. The most fun part of this demo was using my powers to skip challenges and look for secret places, so make sure the game is full of those. The music is really nice, but I feel it's somewhat unfitting, even if it really grows on you. Something I didn't like were the leap of faith kinda jumps, they are somewhat unfair and make you try to save your jumps in case there's going to be a challenge ahead, instead of being able to jetpack around the level like a madman (which is fun and should be encouraged). Also the fact that there's a sound when landing with high horizontal speed but not when falling with high vertical speed feels really odd.
Overall, I really enjoyed this. Looking forward to the full game. Keep up the good work!