With a simple base mechanic you managed to add a lot of content to this game! I really enjoyed the levels involving the boxes physics.
With the unreal engine, I really loved the lighting overall. The visuals are simple but effective, shaping a great overall theme to the game. Loved the box physics as well, although I can't throw it that well haha. One small thing I noticed was that the invisible wall is casted directly above the ceiling, making some interactions a bit unexpected. A suggestion to that would be to either add the invisible wall as an invisible extension to the walls or to make it semi-transparent---so the player knows there is a bound up there. Hopefully I explained this haha my wording is a bit weird.
The game has a fair amount of difficulty but is extremely enjoyable! I wasn't able to get past the final level though.. I didn't have enough time to get 4 balls. However, the amount of new mechanics introduced there is really impressive!
Great job!