How many rods?

A: They are the same shade

The overlapping black arc segments appear to form a spiral; however, the arcs are really a series of overlapping concentric circles.

The dots seem to appear and disappear at the intersections of two lines crossing each other vertically and horizontally.

When you keep your eyes directly on a single intersection, the dot does not appear.

The cube from a different angle

A vase or two faces?

wrong picture

impossible triangle

impossible stairs

thanks ! we all like this
These pictures can relax emotion.

Look at the black spot and move your head forwards and backwards



http://www.cut-the-knot.org/Curriculum/Geometry/RevolvingCircles.shtml

A: They are the same size but the bottom appears to be bigger