That was quite charming! The mechanics are competent. The level design was intriguing and mostly fair; I only got truly stumped by the first box puzzle (it's much harder than it first appears!). The art and character design is proficient; I especially like the background art!
I appreciate the remappable controls; the default control scheme is a bit difficult for the mid-air size changes.
It seems like I can only throw boxes to the right. I'm not sure why.
The web viewport doesn't scale down to fit the window; it's only possible to play fullscreen (I tested this on both Firefox and Chrome).
All-in-all, good work!