sloping floor

I was in a huge auditorium with shiny wooden floors and raked seating, enough to seat several thousand people. The floor sloped down toward the stage and the auditorium was empty apart from a woman I know and me. I was in there to collect something I had left behind. I searched the identical rows, looking for the seat where I had been sitting before the auditorium emptied. I located it and found the thing which I cannot now recall. I was preoccupied by the sloping floor that seemed to be steeper and more slippery than before. I called out a warning to my friend and stepped out of the row into the side aisle and, sure enough, I started to slide, to skate, rapidly down the floor, which was now a very steep hill, toward the flat brick wall under the raised stage. I rocketed down at an alarming speed and tried to prepare myself for impact. I thwacked into the wall but was unhurt. I could then see a few other people doing their best to negotiate the dangerously sloping floor as they shot toward the same brick wall.