Place a digit from 1-9 in each cell such that there are no repeats in any row, column, or box. Cells separated by a single knightâs move (in chess) may not contain the same digit. Adjacent digits on a green line must differ by at least 5. A digit in a red cell indicates the position of its column number within its row. For example, if R2C1 is a 3, then R2C3 is a 1.