Normalish sudoku rules apply: Every row column and 3x3 box contains the digits 0-9 once each. To enable this, one cell in each row, column, and box is a Schrödinger cell (S-Cell): it contains two digits. For the purpose of the other rules, the value of an S-cell is the sum of its 2 digits. The values of the digits contained in the small white circles must each appear at least once in the 4 surrounding cells. For example, at least 3 of the 4 cells around the circle in R89C67 must have a value of 6. Blue lines must have an equal sum N within each 3x3 box they pass through. Eg r1c3+r2c3=r1c4+r1c5+r1c6=r1c7+r2c7. If a line re-enters a 3x3 box, each segment sums to N separately. Different lines may have different values for N.