I would add some music and sfx. You can use Bosca for music and Bfxr to generate sfx. It is easy to use. I don’t understand how the portal works because it looks like you need to push the box out of the screen. You should add some colliders out of the playing area so the player won’t be able move out of it. You can use game object’s layers and colliders matrix to achieve it.

Hey, nice game. In the first level, I carried the box too far away and it went out off the screen.  Also, you could improve some of the art and UI things, but I liked the idea.