23 lines drawn on a light-grey piece of paper, forming the outline of 24 shapes, of which 8 are coloured in a slightly transparent black.

Photographed then digitally modified by adding white and two different shades of grey, each only partially opaque, to most of the remaining spaces which were themselves  first further divided by a thin tracing of the original uncoloured drawing scaled up a little, then flipped 180 degrees, and layered under the initial, thicker lines.