Thanks for playing! Do you mean you had trouble "snapping" the boxes together? I'd love to know which levels, to see if that was intentional design or an oversight :)
On level 5, that's a collision bug, the "easy" way to get the star is to land on the floor above it, then do left/right quickly to fall towards it
Level 6 is intended to be taken when you've reached your final form, and on level 9 you just have to jump up as soon as you spawn, but if you move around, it becomes very hard :p