I got up to here and then it stopped responding to both swipes and WASD:
I am using Edge with WebKit.
As for your questions:
- I would say a 3, maybe 3 and a half.
- Lack of planning ahead! But seriously, i do not think there was anything that was more challenging than the others for me.
- I also would say a more satisfying ending. Or a progression through a couple of different regions/themes.