It's fake - "noclip" on the last level to get around the map.

Exact instructions:
add -console to the game shortcut
open console, type: sv_cheats 1
goto the last level
open console, type: noclip
fly!

Ahh, I figured it would be something like that. Still neat, thanks for the info antonye.

Fake, but still cool to watch.

upvote for the song. is that made with vocaloid maybe?

antonye, are your instructions for a console? cuz I'm playing it on PC and have no idea what you are talking about?
ohhh cheats... nm I understand now, g'duh g'duh

Iavoll, its a voice actress that is recorded and then put through manually controlled filters. The commentary mode has loads of information from the voice actress herself.

I wouldn't vote..only cause the video passes itself off as a hoax.

It's not clear to me how noclip makes this a fake, although I suspected from the beginning that it was.

Because it's cheating, so you can't do this within the true bounds of the game.

I'll upvote it as long as we can add *lies to it.

Adding video to channels (Lies) - requested by Krupo.