Normal sudoku rules apply. (ie place the digits 1-9, once each, in every row, column & 3x3 box). A digit in a circle indicates how many circles contain that digit. Place some circles in the grid such that a box “m” contains exactly “m” number of circles. (Boxes are numbered in normal reading order so the top left box of the grid is box 1, the bottom right box is box 9, etc). ie Box 1 should have 1 circle; box 3 should have 3 circles; etc. If a cell, eg R1C1, contains a circle then all the cells beneath it in the grid (8 cells in this case) must contain circles. No two 9s in the grid can be separated by a single Chess King’s or single Chess Knight’s move; but every 9 must share a diagonal with at least one other 9.