Normal sudoku rules apply. Adjacent digits along the line have a difference of at least 4. A digit in a coloured cell must form at least one sum of 5 or 10 with a digit in an orthogonally adjacent cell. A digit in a white cell must not form any sum of 5 or 10 with a digit in an orthogonally adjacent cell. For example r2c5 and r3c6 cannot be a 3 or an 8. However, one or both of r2c7 and r1c6 must be a 3 or an 8.