Place the digits 1-9, once each, in every row, column and region. The regions must be determined by the solver. Each region is a set of nine orthogonally connected cells. If a digit N is in a circle then exactly the next N cells in the direction of the arrow (and only those N cells) are in the same region as that circle. eg if r6c5 was a 2 then r6c5, r5c6 and r4c7 would be in the same region and that region would not include r3c8 or r2c9.