STEP 1

THE bottom-left foursome add up to 28 and the three dark cells add up to 20. 28 - 20 = 8 . . . so you can write 8 in the middle-left cell. Do the same sum for the top left foursome. 18 - 13 = 5 . . . so the central cell must be a 5. Now, the dark cage adds up to 20, and one of the cells is a 5, so the other two must add up to 15. That can’t be 8 + 7, because you’ve used the 8. So it must be 6 + 9. There’s no way to know which way round they go yet, so just scribble a tiny 6/9 in each cell.

HERE’S one of the surest ways to get started with a Suko. When a group of four cells, such as those around the number 28 here, contains a ‘cage’ of three coloured cells, a simple sum gives your first number to fill in.