The final offering of older works (until I can find some more) is this one, called “Observation.”
While it might seem to lack detail, I think this one works well all the way through, including the title. The relevant question is, where is the observation taking place? You can probably see the “eye” near dead center. But is it an eye? What are the ghost shapes in the background? And so on. There’s a lot of subtle stuff happening in this one.
Not everyone agrees, of course.