Very interesting game ! The hook physics was unusual, but having grandpa showing how to do everything made it easier to understand ^^ ! The level design is good, the story is great and the game is really polished, with its cutscenes, cute graphics and fitting audio.
In fact, my only issue was the spikes : you sometimes can't see them very well (on a grey background, especially) and their hitbox extend above their sprites, making a lot of death feel unfair, because I didn't visually touched the spike and still died.
But that's just a detail, everything else is on point, congratulations =) !