I made the 6 levels, quite easy when you understand some tricks (the side can touch wall, but not the borders). It needs longer levels and of course more of them... 3.5 to make you want to do better ! ;)

Something happened during the fourth level. When I hit something the level restarted but with my box flung into the air. This made it a bit hard to continue as my box is bouncing and such. Dunno if this is intended, but other than that, there was nothing wrong with it.

You could add more levels, and some moving objects.