Light Up · how to play
Light every cell.
The rules
Place light bulbs on the white cells so that:
- Everything is lit. A bulb lights its own cell and shines down its row and column until a wall blocks it. Every white cell must end up lit.
- No bulb lights another. Two bulbs can never see each other along a clear row or column.
- Walls count. A numbered wall must have exactly that many bulbs in the cells directly next to it (up, down, left, right).
Every puzzle has one unique solution.
How to play here
Tap a white cell to cycle it: bulb 💡 → mark clear · → empty. Lit cells glow warm; cells that break a rule (two bulbs seeing each other, or a wall with too many bulbs) light up red.
A starting tip
Start at the numbered walls. A 0 means none of its neighbors can hold a bulb — mark them clear. A wall whose open neighbors exactly equal its number must have bulbs in all of them. These forced moves cascade into the rest.
Interactive
Light up the grid together
Step 1/2:The '1' wall (row 1 col 2) needs exactly 1 bulb next to it. Its neighbors are (0,0), (0,2), (1,1). Place a bulb at row 1 col 1 (top-left). It lights the whole first row and column!
Tap the top-left cell.
Tap a cell: place a bulb → mark it no-bulb ● → empty. Light every white cell. Right-click cycles backwards · Cmd+Z undoes.
Next: Light Up strategiesSaturated clues · Zero walls · Diagonal of a satisfied clue — solve faster, never guess.