Light Up
About the game and how to play
Light Up, also called Akari, is a Japanese logic puzzle. You place bulbs on white squares; each bulb lights its whole row and column until a black square blocks it. Light every white square, but never let two bulbs shine on each other. Numbers in black squares tell you exactly how many bulbs touch them.
- Players
- 1 player
- Category
- Logic puzzles
- Price
- Free, no download, no sign-up
- Where to play
- In the browser on phone, tablet and computer
How to play
- Place a bulb on a white square — it lights its row and column up to a black square.
- No bulb may light up another bulb.
- A number in a black square is exactly how many bulbs share an edge with it.
- Light every white square to solve the puzzle.
Tips
- Start with the certain numbers. A 4 gets bulbs on all four sides, a 0 rules out all its neighbours, and a number equal to its count of open white neighbours (such as a 2 in a corner or a 3 on the edge) fills every one of them.
- Mark cells that can't hold a bulb with an X, either by tapping a bulb again or by switching to X only mode: the neighbours of a 0, the leftover neighbours of a satisfied number, and every cell that is already lit, since a bulb there would shine on another bulb.
- Hunt for dark cells that can only be lit one way. A white cell boxed in by black cells or the grid edge on every side must hold a bulb itself, and if only one remaining cell can light a dark square, the bulb goes there.
Frequently asked questions
What about black cells with no number?
They only block light. Any number of bulbs, including none, may sit next to them, so leave them out of your counting.
Is there only one correct way to place the bulbs?
Yes. Every generated puzzle, including the daily, is checked by a solver to have exactly one solution, so each bulb can be found by deduction.
How do hints work in Light Up?
A hint first removes a bulb that isn't part of the solution. If all your bulbs are correct, it places a bulb that a numbered cell still needs, or otherwise reveals one bulb from the solution, with a short note saying which it did.
How big are the Light Up boards, and what level is the daily?
Easy is 7×7, Medium 8×8, Hard 10×10 and Expert 12×12, with fewer numbers on the harder levels. The daily puzzle is an 8×8 Medium board that is the same for everyone; it changes at midnight Baku time (UTC+4), and older ones can be played from the archive.