Simple Coloring
Extreme
Used by Smart Hint
Chain every cell where a digit has just two possible spots in its unit, alternating two colors — a contradiction or a shared sight line lets you eliminate.
- First colour in the chain
- Second colour in the chain
- Where the conclusion lands
- Candidate ruled out
How it works
- Digit 5 forms a chain of strong links: A1 ↔ A5 (column A's only two candidates), then A5 ↔ G5 (row 5's only two candidates) — colored teal / red / teal as the chain alternates.
- D5 sits in row 5 alongside both a red and a teal link. Since one of every red/teal pair must be true, any cell that sees both colors can't be 5 — eliminate it there.