This reminds me of the 'Tetris effect' in which people who play Tetris for prolonged periods of time will begin to experience Tetris-like hallucinations when they stop. I've experienced it myself and have trouble explaining it, but it's as though everything you see becomes Tetris-like in some way. You look at your dinner and see ways to rearrange the peas so they 'fit' with the mashed potatoes, or something like that. There's more to it than that though, there's a real sensation of things being moving blocks that must be fitted together. It's bizarre.

But unlike Quake, Tetris isn't providing you with a 3D experience. That makes me wonder how much overlap there is between the two experiences.

I took an art class a few years ago. Negative space drawing and perspective drawing will blow your mind after a 3 hour session.

Walking outside you see lines and shadows everywhere. Entire perspective changes.