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Puzzle paused
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Light Up
Place light bulbs on a grid of empty cells and walls so that every empty cell is lit. Each bulb shines along its row and column until a wall blocks it.
Rules
- Place bulbs on empty cells so that every empty cell ends up lit.
- A bulb lights its whole row and column until it hits a wall.
- No bulb may light another bulb.
- A numbered wall shows how many bulbs are placed in its four directly adjacent cells (up, down, left, right).
Controls
- Click an empty cell to place a bulb. Click it again to remove the bulb.
- Right-click an empty cell to mark it with an X (a reminder that no bulb can go there). Right-click again to clear the mark.
- On mobile, tap a cell to cycle through empty, bulb, and X.
Tips & Tricks
- A "0" wall means none of its four adjacent cells can be a bulb. Cross them out.
- A "4" wall has bulbs in all four of its adjacent cells, so place them straight away.
- If only one cell can light a particular empty cell, that cell has to be a bulb.
- After placing a bulb, mark every cell along its row and column (out to the nearest walls) as no-bulb.