[SP] BubbleNut Zero
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PREY has all these. It was released in 2006, and I used to map for it before the community died 
You really should check it out for the nausea-inducing effects.
Thanks man, someone suggested that a few weeks ago - I'd completely forgotten =)
Edit:
Wholy crap, that looks amazing... nobody mentioned portals, light bridges, and becoming six inches high 
http://www.youtube.com/watch?v=T0XwjoxK ... re=related
You can actually see the room rotates from your observation point.
That looks like a really slick map!
By rotating it smoothly (instead of pretending you're walking on walls), the whole thing seems a little more predictable. Cheers, given me some ideas also 
I noticed some of the same things other posters have mentioned, about the cube and the lightbridge. I don't even know what the lightbridge was for; I never used it. After turning it on and turning the room, it apparently didn't turn, leaving a white line at an angle across the room, not going from the source of the lightbridge, but ending near the same room as before. After turning the room again, I pushed a cube against the button, and the bridge was coming from the source again, but only as a white line.
As proof-of-concept, it's only about 40 proof; it needs some more refining to be really good stuff. 3/5 from me.
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Crap, forgot to reply..
Cheers for that KK, most of it should be fixed now =)