Or suppose a large stage (blue) within the traditional proscenium arch, but with an additional acting area (green) in the middle of the room.  Each square in the yellow area contains a pair of seats that pivot around a vertical post.  If the action's up on stage, everybody turns their seats to face that direction.  If the stage lights go down and one or two performers move to the green area, everybody shuffles their feet to turn their seats 90°.  The real advantage is to the audience in the non-swiveling seats in the rear of the auditorium, who get to see the performers at much closer range when they're in the green area. (The letters indicate floor height in steps:  b is 9" higher than a, c is 9" higher than b, and so on.  All the yellow seats are on the a level, with the actors standing on a stage that's three or four steps higher so that they can be seen.)