The best thing about your game is the lovely atmosphere you were able to create with simple lighting and shapes. Also, the particle effects were put to good use. If I'm being critical, I'd say that while it might be tempting to type down your tutorial in the description and leave it there, it's best to let the players know the controls within the game as far as possible. In my own playthrough, I was completely unaware that you could use the Tab button to switch cameras. So you see the obvious drawbacks of the approach you took.
Furthermore, the point where your game lacks - in my opinion - is the fun factor. It offers little to no replayability and there's not much incentive or feedback to make moving the cubes fun.
I'm sorry if I sound harsh. I know there'll be a lot of comments saying it was excellent and pointing out only the good aspects of the game or just leaving a general comment saying it was good. Trust me, those comments are there to make you feel good and get you to leave good comments and ratings on their game as well. However, I truly want to give you an unbiased perspective on the game so that you can walk away with a few insights from the perspective of a player that you, as a developer, might not have been able to uncover and consequently, use this knowledge to improve your games in the future.
TL;DR: Loved the atmosphere and the particle effects. Improve tutorial and feedback system.