Already Lit
A cell that is already lit can never hold a bulb — whatever lights it would be looking straight at it.
How it works
- 1The bulb on the left of the middle row lights everything it can see: the whole row, and the whole column above and below it.
- 2So the marked cell further along that row is already lit.
- 3Putting a bulb there would mean two bulbs staring straight down the same row at each other, which the rules never allow.
- 4It has to be empty. This is the most common move on any board — every bulb you place empties a whole cross of cells for you.
- Cells that establish the pattern
- Cell this technique rules out