Seriously guys, there's no way to invert the Y-axis? Is there a recommended 3rd-party program for temporarily holding the mouse upside down? Right now I'm running around the hallways staring at the floor and losing track of my direction because I can see is a contextless ceiling...to say nothing of hitting things when they're still halfway across the room.

Ugh. I found it.

It's not in "controls" where everybody else puts it, and it's not about the Y-axis. It's in "gameplay", where the true/false setting labeled "Invert look" is. No mention of the mouse, nor of the Y-axis.

But I can play it now.