Magikmike; indoor, just a cardboard box, like the one of removal, makes the pleasure of a cat.
Yes, the cat doesn't think as human, & I asked me what color the cats should to prefer? I see just one answer, the colors that exist in nature; so green, colors of bark of tree, or some colors of stone. The cats are animals very fussy & not easy, with a strong mind of contradiction (be a dissenter). As any animal, they have the ability to feel what you think. So sometimes I accuse them to make intentionally the contrary, just to say to you: "Hey biped! it's me that decides; not you".

A house: http://www.hortondome.com/dome/ (nice outside, but inside it's dubious; as too much geodesic houses).