Sit an arm's length away and look through the picture, as if at something behind the screen.
Let your eyes go lazy. Do not try to focus — trying is what stops it working.
The dots will drift, double, and then lock. A shape lifts out of the page.
Hold still once it appears. It gets clearer the longer you leave it.
Guess it between yourselves first. The reveal button is there for afterwards,
or for whoever cannot get their eyes to do it — roughly one person in ten
never can, and that is not a failing.