Low Corner Clue
A 0 or 1 in a grid corner rules out both outer sides, because those two sides must match.
How it works
- 1This cell sits in a grid corner — its corner dot touches only these two edges (top and left), nowhere else to go.
- 2A loop can never dead-end, so that dot needs exactly 0 or 2 lines — meaning top and left always match: both lines, or both blank.
- 3With a clue of 1, both being lines would already total 2 — too many. So both must be blank. (A clue of 3 or more works the same way in reverse: both would have to be lines.)
- Edge ruled out
- Cells that establish the pattern