How to play Light Up

The goal

The rules

• A bulb lights its own square and every square in its row and column, until the light hits a black wall or the edge.
• Two bulbs may never shine on each other: no two bulbs in the same row or column with only white squares between them.
• A number on a wall says how many bulbs touch it, directly above, below, left or right. Walls without a number can have any number of bulbs around them.

Playing

• Tap a white square to place a bulb, and tap it again to take it away.
• Hold a square to mark it with a dot, meaning “no bulb here”. Dots are just notes for you.
• The Bulb / Mark switch under the board swaps the two, so a tap places dots and holding places a bulb.
• Undo takes back your last change.

Checking your work

• Lit squares glow yellow.
• Bulbs that shine on each other turn red.
• A number fades once it has all its bulbs, and turns red if it has too many. A 0 fades once every square around it is lit or dotted.
• The puzzle is solved the moment every square is lit and every rule is met.

Tips

• Start with the 4s (bulbs on all four sides) and the 0s (dot every square around them).
• A 3 against the edge or another wall has only three places for its bulbs, so fill them all.
• Look for a dark square that only one square can still light: that square needs a bulb.

Difficulty

• Easy: a 7×7 grid with plenty of numbers.
• Normal: a 10×10 grid that can be solved step by step, with no guessing.
• Hard: a 12×12 grid with as few numbers as possible; you may need to try a bulb and see where it leads.
• Every puzzle is new and has exactly one solution. Your best times are kept for each difficulty.

Keyboard

• Arrow keys move, Space, Enter or B places a bulb, X or . places a dot, Backspace clears, M switches the tap tool, and Ctrl or ⌘+Z undoes.

Questions

Strategy guides