The idea is interesting. I like that you can kill the cube in the air to create a platform. I had to figure it out since I thought the "corpse" would be affected by gravity. The fact that, when you die, you have to watch all of your past moves to actually play again makes it have a lot of dead time in gameplay.
Also, I would add a "reset" button to restart the level from zero, since it's not hard to kill a cube in a place that simply prevents you to move.
Feedback aside, congratulations on reaching the deadline! That's a victory in an of itself :)