Amazing ! The music is great and the graphics are cool.
The gameplay is also really great overall. Some tips to improve the game would be to use "Input.GetAxisRow" so the input value is either 1 or 0, so your cube doesn't take the time to speed up.
Second thing, i had some white lines in the background, when i was jumping.
And third, try to use "interpolate" or something so it feels smooth when you're moving the cube.
As I said, really great game overall, i had fun playing it.