Normal sudoku rules apply. Clues outside the grid shows the sum of the digits sandwiched between 1 and 9 in that row or column. Digits in column 1 indicate in which column the digit 1 is placed in the respective row. So, for example, if r7c1 was 6 then 1 would be placed in the sixth column of that row ie r7c6. Columns 5 and 9 have the same rule for the digits 5 and 9 respectively. Each red stripe contains exactly the same sequence of nine digits in the same order (the “slot machine”). The sequence can start at any point along a red stripe, and when it reaches the bottom, it wraps around again to the top.