In terms of playability it's accessible and easy to grasp. The different cube levels are learnt almost instantly and it doesn't take long before you realise grey cubes run into each other and then die. I do have some problems with the game in terms of playability though: as pointed by another comment: running into a cube that just spawned behind you is very annoying. It would be nice if the cubes made some sound as they moved and if there were either dedicated spawners or waves of enemies (with a certain time limit that, if not fulfilled, just continues to the next wave and keeps the current enemies).
Art wise, you can use primitives, but play around with them to make them look nicer. A change in shader changes a lot, and a bit of playing around with lighting and implementing post processing could have done you so much help.
The music was weird but a nice background follower which isnt annoying so that's good.
It doesn't fit the theme however. The game says two things and that's about it. Not very interesting and it's just one lie. Definitely shouldnt inspire the title to your game.
All around it's a good base design, and honestly a good implementation in terms of raw playability (except for the problems I adressed), but it really could use an artistic redecoration.