Idea for a torture device that came to me in a dream.
I call it “The hammer that never comes down”. It consists of a small pit, like a well. It is completely pitch black.
The victim is placed at the bottom. A sliding rubbery lid is placed into the opening of the well that slides down slowly so that the victim has less space to move and breathe.
The victim can push or kick the rubbery lid up slightly. With every kick or jump the lid goes slightly up but also starts slowly going down again. The lid is possible to be pushed all the way up to the top of the opening of the well, where, still covering the opening so that the victim cannot escape, little openings in the lid are exposes so sunlight and fresh air comes through. Then the lid starts slowly going down again.
With useless toil of pushing the lid up to the top, the victim can enjoy some sunlight and air. If he does not push the lid up, he has little breathing room and room to move and lives in total darkness.
I made a rough illustration of how it would work.
