Original idea, which stays quite simple at its core, but offers some interesting enough gameplay. I would be curious to see how far you could get with this (a NPC stealing my control cube and going away with it ?). The art is also nice by the way.
The level design is quite limited and short, but you managed to prove the concept quite well !
When I'm holding a cube into the world (drag&drop but without releasing the mouse click), I would expect the camera to stay centered on the cube I think, so that it's easier to prepare the cube, jump, drop it, without the cube being moved at the same time of the camera.