Light Up Free online game

What is it?

Light Up is a logic puzzle where you place bulbs on white cells to light up the whole board. Each bulb shines across and down until a wall blocks it. The rules are the same as the puzzle known as Akari.

Bulbs must not shine on each other, and a numbered wall needs exactly that many bulbs right next to it (above, below, left and right). The puzzle is done when every white cell is lit, and every puzzle has exactly one answer.

How to play

1. Tap a white cell to cycle: bulb → dot (no bulb) → empty
2. Bulbs shine across and down until a wall blocks them. Light every white cell to finish
3. Bulbs can't shine on each other, and a numbered wall needs exactly that many bulbs right next to it

Difficulty and rankings

There's a weekly ranking and an all-time ranking; the weekly one resets every Monday at midnight (Korea time). For details, see the Help.

Good to know on Hanpanmadang

• Boards are 7×7, 9×9 and 10×10. Easy and Normal can be solved with the numbers and 'only one light source' alone, while Hard always needs at least one round of trial reasoning, placing a bulb to see if it leads to a contradiction.
• Lit cells glow yellow. A numbered wall turns green when it has the right number of bulbs and red when it has too many, and bulbs that shine on each other turn red.
• Hints explain the reason instead of giving the answer, and each one adds 30 seconds to your time. Dots are just notes that a cell has no bulb, so they don't count toward the answer.

Common mistakes

Placing bulbs by looking only at the numbered walls.

Even if the numbers fit, the puzzle isn't done while dark cells remain. Also check where narrow cells boxed in by walls can get their light.

Putting another bulb on a cell that is already lit.

A bulb on a lit cell makes two bulbs shine on each other, and both turn red. A cell that is already lit is never a bulb spot.

Treating dots as part of the answer.

Dots are only your own notes. If you put a dot where a bulb belongs, the hint will point it out in red.

Tips

• No bulb can go next to a 0 wall, so mark those cells with dots first. A 4 wall gets a bulb on all four sides.
• When a wall has as many open neighbors as its number, like a 2 in a corner or a 3 on an edge, every one of those neighbors is a bulb.
• If only one cell can still light a dark cell, that cell must hold a bulb. This often happens in narrow spots surrounded by walls.
• A cell that is already lit can't hold a bulb. Tap a cell that must stay empty once more to mark it with a dot, and you'll make fewer mistakes.