The physics is very impressive. And despite the occasional swift acceleration, it never feels like the character is completely out of control, or that the camera is in the wrong place--well done. The visual design is also excellent, achieving absolute clarity in spite of the very limited color palette.
I would add in the instructions on the game page that, in order to provide the extra boost, you have to hold down the X key simultaneously with the Z key. It may seem obvious, but it confused the heck out of me for several minutes.