Excelent. Graphics, animation, sound and intro are amazing, very profesional look.
Other comments have already talk about difficulty, so there is not much i can add. Anyway, i can understand this difficulty level on a short game for a jam, as there is no more content waiting ahead. Perhaps you can give a few seconds of breath after you restart, as sometimes you almost pop up in front of a box.
Extra points for letting people restart in any moment, not forcing the player to wait till the score shows up. I think this is important for this kind of games.