Normal 6x6 sudoku rules apply. (Place the digits 1 to 6, once each, in every row, column and region). Yin Yang: Shade some cells such that all shaded cells form one orthogonally connected area, as do all unshaded cells, and no 2x2 area is entirely shaded or unshaded. Counting Yin Yang: A digit in a shaded cell shows how many times that digit appears in shaded cells. Quadruples: A digit in a circle must appear in the surrounding 4 cells. If a digit appears twice in a circle, it must appear twice in the surrounding 4 cells.