3D Medusa
Extreme
Reference only
Simple Coloring extended across multiple digits at once — bivalue cells link candidates of different digits into the same two-color chain, unlocking more elimination rules.
The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.
- First colour in the chain
- Second colour in the chain
- Where the conclusion lands
- Candidate ruled out
How it works
- A1 ↔ E1 links on digit 5's bivalue cell (A1 is {2,5}), and E1 ↔ E5 links via a strong link on 8 — the chain now carries two different digits instead of Simple Coloring's one, colored teal/red as it goes.
- A5 shares its row with the teal-colored A1 (digit 2) — but A5 also sits in E1's row where a red-colored cell claims a different digit. Cross-digit rules like this are 3D Medusa's extra leverage beyond single-digit coloring.
- Not yet in GridWits' live solver — reference only, since correctly implementing all of Medusa's elimination rules needs more verification than a single pass allows.