Simple coloring
MasterSimple coloring follows one digit. Wherever a row, column or box has exactly two places for it, one of the two holds it: color one cell blue and the other green, and carry on from cell to cell. In the end, either every blue cell holds the digit or every green one does.
How to spot it
- Pick one digit and find the units where it has exactly two places.
- Starting from one of those cells, color the cells along these links in two alternating colors.
- If two cells of one color see each other, that color is false: remove the digit from all its cells.
- A cell that sees both colors can’t hold the digit either.
Why it works
Each link means exactly one of its two cells holds the digit, so the colors alternate between true and false. One whole color is true, the other false.
Example
7
9
6
1
9
7
3
9
7
5
7
3
5
8
9
4
1
1
3
8
9
7
9
8
1
7
4
3
5
7
9
4
3
1
8
2
2
1
7
9
1
9
7
Follow the 6s that have only two places in a row, column or box.
Common mistakes
- Linking through a unit where the digit has three places: only two places make a link.
- Mixing two separate chains in the same colors.