How to retract the walls

  1. Press the left arrow key ( ← ) to expand the aperture.
  2. Press the right arrow key ( → ) to contract the aperture.

When the aperture is fully closed you see the fundamental cell from which the space was made. When the aperture is mostly open you have the illusion of seeing a much larger space, tiled by repeating images of the fundamental cell. You see this illusion because your line of sight wraps around the finite universe, in effect letting you see yourself from behind, from the side, from above, and so on.