I had a lot of fun with this game! The concept is very interesting too!
Though I have some problems with the grappling hook specifically. I don't know if I am just not very skilled (very possible haha) but I never managed to get the hang of it. I think that this boils down to two problems. Firstly, the grappling hook is activated both with the left click and space bar (meaning that the space bar is used both for jumping and grappling) and secondly you have no way of choosing which anchor point to use with the grappling hook. I don't understand how the game chooses which anchor point to use as it doesn't seem to pick the closest one. The grappling physics seem a bit off too, but I can't quite place what is wrong.
Also, I found that 'K' to age is a bit of an odd key to use, it's difficult to reach when platforming or mid-jump.
Still I really loved this game and especially the art / audio!