Working on peghole. The rules: only 3 block-shapes and their rotations or reflections: square, quarter circle and ‘chopped’ square (see the image). Small grid size: x-height only three blocks high (hard in the three storey characters: e, s, z… and the x…). Square innershapes favoured.
Made a filler as supplement. That was the easy part. Overprint the regular over the filler to get a constructivist feel. Hardline avantgardists might even use the filler pure and undiluted. Brave! Heroic! Unreadable?