I really like this one - I think the box making mechanic is a pretty neat idea, I like the cute look of the main character, and I liked the audio!
Really, I think the biggest weakness is that I'd put more platforms lower down at the beginning to make it slightly easier to start and then get progressively harder, but that might honestly be a matter of personal preference.
I have to say well done on this one!
Oh, and I also liked how the boxes had physics when getting hit by the cannonballs; that made for an interesting surprise while building!