How to Solve Light Up Puzzles
In Light Up you place lamps so every open cell is lit, no two lamps shine on each other, and each numbered black cell has exactly that many lamps beside it. Logic does all the work.
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1. Learn the three rules
Every white cell must be lit. A lamp lights its whole row and column until a black cell stops it. Two lamps may not light each other. Numbers show how many lamps touch that black cell.
2. Start with the zeros
A black cell marked 0 has no lamps next to it. Mark those neighbours as empty and your first deductions are free.
3. Fill cells that equal their number
If a clue has exactly as many free neighbours as its number, every one of them must be a lamp.
4. Light the lonely cells
If a white cell can only be lit from one spot, put a lamp there. Cells with a single option are forced.
5. Mark impossible cells
Once a cell is lit, no lamp can go there. Mark it so you stop considering it, and the board opens up.
Frequently asked questions
- Do I need to guess?
- Well-made puzzles can be solved by logic alone. If you are stuck, re-check the numbered cells; a missed clue is the usual cause.
- What does a black cell without a number mean?
- It only blocks light. It has no lamp requirement.