This technique is satisfying to spot - and you'll need to get used to this!
It works by supposing what would happen if you circled each occurrence of several possibilities for a number in a row or column, and finding that circling one would cause an impossible situation. |
| In this example, circling the 7 in cell (2,7) would force you to paint both 7's in cells (2,2) and (2,4). But this would not be allowed, as we would then be dividing the white cell in cell (2,3) from the remainder of white cells on the board. Hence we must instead paint (set) the 7 in cell (2,7). |
