Possibly the best case is a door that opens both ways. With that out of the way I feel like this needs to go further and be more adaptible to different doors/contexts.
My first quick suggestion based on how I hold my hands when pushing/pulling is to define horizontal = push and vertical = pull. That way there is still enough freedom to adapt the concept to the individual door/room/building.
An other, idiot proof, way might be making the push side unpullable (just a flat surface on the door, without an undercut or nook to pull on), and make the pull side unpushable. Maybe a rope, though that seems tacky, but working with a flexible material that communicates that pushing makes no sense might be cool.