Not bad! I liked how you introduce each level and have the bit of "dialogue" which helps immerse you a bit more into the game world. The levels were also nice designs.
It's a little buggy though. I managed to get to the end but playing without keyboard controls was kinda tricky, and there's something funky with the jump physics (i used spacebar) and platforming as you'll see in my playthrough, so it would be great if they could be ironed out.
Would love to see Cubey in future adventures once he gets the laws of physics more solid! Great job!