The upper-left element gets laterally inverted in first, third, fifth. .... steps; the upper-right element gets rotated through 180 o is first, fourth, seventh,.... steps; the lower-left element gets laterally inverted in second, fourth, sixth, ... steps; the lower-right element gets rotated through 180 o in third, sixth,... steps and the pin at the middle-right position gets laterally inverted in every second step.