[acron0]

I agree with the points about FPS games. I played a couple of the demos without any nausea and then tried HL2 and my stomach was almost instantly in my throat. On reflection, there was something about the first two demos that made the difference, I think. In one, you're underwater in a pod, which means even though you're in first-person, there remains the concept that it's not you moving, but the pod, and you therefore have a relatively static near-plane environment which moves subtly, whilst the 'outside world' moves more freely. In the second demo, a sky-diving simulator, you're free falling, so there's very little rotation involved.