This was a pretty decent demo, some things i would probably fix would be the collision detection for the ball/walls (im guessing this was made in gamemaker, in which case it's probably to do with the masking of the objects, using a uniform square mask would probably help) same with the boxes, i would restrict them from moving toward the direction of the wall they are touching to prevent them from ghosting through the walls. Over all though, most of the mechanics were functional and i was able to get to the end screen without too much trouble. With some polishing and updating the visuals a bit this could be a good game.