a unicellular prism has zero room
zero_dimensional_thing is spatial_thing. window_blind is collapsible_thing. fitting_room has large_mirrors zero_family_room_dwelling is single_family_residence. unicellular_algae is single_cell_organism. quadrangular_prism is prism. dark_places has no_light unicellular_algae is algae. flat has at_least_one_doorway every_room has door