Love the idea with the balloon, and it was very fun! It was a bit hard to get the balloon to the size you wanted though, and it was a bit annoying to have to hold shift for most of the game, maybe you should just press shift to switch between deflated and inflated balloon isntead? But I still really enjoyed that idea and it was fun to use :3
I also like how fair the spike hitboxes were, and the ending was really sweet :)