Normal sudoku rules apply. In addition, the sum of digits along a line must be the same within each 3x3 box the line passes through. eg r9c1+r9c2+r8c3 [line cells in box 7] = r9c4+r8c5 [line cells in box 8]. Furthermore, each line is either an Entropic Line or a Modular Line. Along an entropic line any run of three cells contains exactly one low {1,2,3}, one medium {4,5,6}, and one high {7,8,9} digit. Along a modular line, the digits in any run of three cells must all have different remainders under division by 3. (ie So one digit must be from the set {1,4,7}, one from {2,5,8} and one from {3,6,9}).