Light Up · strategies
Read the walls first.
Place bulbs so every open cell is lit and no bulb shines on another. The numbered walls hand you the opening moves.
Saturated clues
A numbered wall whose count equals its open neighbors takes a bulb in every one. A 4 is always surrounded by four bulbs; a 3 on an edge fills all three.
Zero walls
A 0 wall bans bulbs from all its neighbors — mark them. Those cells must be lit from elsewhere along their row or column, which often forces a distant bulb.
Diagonal of a satisfied clue
When a numbered wall is already satisfied, its remaining neighbors are bulb-free. A 1 with a bulb placed bans the other three — and anything that could only be lit through them must find another source.
Lonely cells
A cell that no other position can see must hold its own bulb. Scan for cells whose row and column are blocked by walls in every direction — dead-end corridors are the classic case.
Order of attack
Zeros and saturated clues first, then mark banned cells around satisfied clues, then hunt lonely cells. Repeat — each bulb's beams create new banned cells and new lonely ones.