3x3 middle box solve with digits 1-3 and retain 1,2,3 belonging to the rows. 5x5 middle box plus phistomefel ring solve with digits 1-5 and retain digits 1,2,3,4,5 associated with their rows. Middle box plus two outer rings use digits 1-7 and retain 1,2,3,4,5,6,7 relating to their rows. 9x9 Normal sudoku rules apply. Maximum cell, kropki and anti-king rules still apply. German Whispers: Adjacent digits along the marked lines have a difference of at least 5.