Like the art style, and the mechanic seemed interesting and like they'd had a lot of potential. I couldn't get past level 3, with the paper clip, so I can't say more about the level design, but here are some other comments.
It feels like the falling death should be a little quicker, the player needs to be able to restart the level faster so they keep engaged. Also, the death sound is a little loud and annoying, I would change is to something more pleasant, but that still note a negative outcome.
For the cubes themselves, I think the cube should slide as much as they do, especially combined with the sometime hard platforming, blocks just stopped moving when you stop pushing them.
But with a little more polish on the movement, I'm sure it could be a very nice little puzle game :)