Clue Satisfied
A clue with all the bulbs it asked for is finished: every other cell touching it is empty.
How it works
- 1This wall wants exactly one bulb among the four cells touching it.
- 2It already has that one, directly above; the crosses around that bulb are just the cells it lights, ruled out by Already Lit.
- 3So the wall's other three neighbours are empty — a bulb in any of them would give it a second one.
- 4A 0 is the same rule at its simplest, and it is usually the best opening move on a board: it empties all four of its neighbours before you have placed anything.
- Cells that establish the pattern
- Cell this technique rules out