Normal sudoku rules apply. A black dot joins cells with a ratio of 2:1; a white dot joins consecutive digits; an X joins cells that total ten and a V joins ones that total five - not all dots, Xs or Vs are shown. Digits may not repeat in killer cages but their sums will provide a message, from the simple mapping of 0-9==1-10 & A-Z==11-36 (e.g. a cage total of 30 would represent a "T" and 15 an "E").