Zero Clue
A 0 means no edge of this cell can be part of the loop — mark all four sides with an X.
How it works
- 1A 0 says the loop uses none of this cell's four sides — that is the whole content of the clue, so nothing else has to be true first.
- 2Cross off all four sides. The loop still has the rest of the board to run in; it just can't touch this cell.
- Edge ruled out
- Cells that establish the pattern