"How much floor space would it need to take up to comfortably sleep -- or play -- two adults? Four? Six?"
I'm going to suggest for volume measurements something on the way of the Japanese tatami mat system. In Japan, a room is measured in jo which is roughly the space needed for a sleeping mat for one adult. This comes out to just over 1.5 m^2. So I figure if you lay out the space in jo by buying a tatami mat and marking space with it, you'll come out to something which if not exact will be workable enough.
Ooh, there's a good idea. But I'd have to increase it a bit: I'm almost certain that the Japanese conserve more space when sleeping than I do. Good call, though.
The North American Brown Bear probably conserves more space when sleeping than you do. Increasing it is likely a good idea.
Oh, you've heard the stories, then?
That's why I went with a brown, rather than a polar or grizzly. =)
It's their fine features and suave demeanor, isn't it?