For some reason I forgot to read the description so I was also confused about how to start.
I thought it was really well balanced (ha! Sorry...) and generous, if you are patient (I had to pull some patience out of the ether because I'm not sure I would want to play again if I got very far and then died; I was determined to play once and get to the end and I did). I went back afterwards to see what happens when you fall. Hectic.
The audio is very, very good and I like that it's dynamic. I also liked that the camera moved a few times to mix it up a bit visually (although that switch at ~100m is nasty until you get used to it!). I love the art, it's just unfortunate that you spend most of the time looking at the UI and marker instead of the art and animation. I did also notice that the movement didn't always match what I was actually doing.
A couple of minor points and bugs - you can walk backwards at the start (possibly to infinity?, although I didn't go that far) and there's no walk cycle for moving backwards; some of the audio needs normalising and there was a bit of clipping towards the end (plus one loop in the final(?) section of the line has a volume burst that's jarring); and no credits for the samples used in the audio?
Overall, however, a really cool idea and very well executed, plus it's perfect for the theme - I will not ever be doing this in real life. Well done!