I have been getting some good feedback on my game recently but I yesterday I was struck with the first "can't play, motion-sick!" review and that got me thinking about motion/sim sickness and what may cause it.
While spending the last couple of nights testing out jam entries I have only gotten sick/woozy on a couple of occasions. The first trigger has been low/choppy framerates (like the lobby in "the human body" for example) and the second one has been falling (Tightrope). From earlier experiences with HL2 i know that strafing is a big NO for me as well. My girlfriend on the other hand could not take the movement mechanics in Small and Gliding princess (press touchpad to walk), but handled both the Human body and Tightrope without any problems.
In my game we came to an argument about the elevators. I liked the elevators when they moved very slow while she want them to go as fast as possible (just to get it done?).
So, what causes you to feel motion sick?