The latest visual trick making the rounds is an image of intersecting grey lines against a white background, with 12 black dots on the nodes where the grey lines meet. All 12 dots are really on ...

Where the lines meet, there is a black dot with showing 12 in total ... on in the image as you stare at just one part of it. The dots are placed at the intersection of several grey lines.

But the black dots around it seem to appear and disappear. That’s because humans have pretty bad peripheral vision. If you focus on a word in the center of this line you’ll probably see it ...

This route here is a bridleway and it’s marked on the map with a green dotted line meaning it’s a public right of way. But this footpath over here is only marked on the map with a black dotted ...