In the upper right (which resemble Jan Robert Leegte's pastel drawings), we have squares that can be read as "in" or "out"—but which lean to one reading, as we tend to see illumination as coming from above, a reading reinforced by decades of UI design. Most of these were rejected for the bleeding problem, a lack of wire insulation: reading one part of the circuit tends to jump across to nearby wires it should not directly affect. However, even if practice is needed to read larger circuits, they don't require understanding special symbols or knowledge of logic gates to follow, relying on our perception to unlock.