The entire position after each half-move, except for the white pawn, shifts down one row at a time during a repeating move pattern (sevenfold echo!). The pattern extends from move 2/6 to move 4/8. Compare the positions reached with 2.Kg2/6.Be3, 2...Kg4(Kh5)/6...Kg3(Kh4), 3.Bf3+/7.Bf2+, ... and finally 4...f6/8...f5.
