Play Light Up puzzle (Light Up) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Light Up is a placement puzzle: put light bulbs on a grid of white and black squares so that every white square is lit, while no two bulbs shine on each other. Numbers on the black squares say how many bulbs touch them. Nikoli publishes it as Akari. The puzzle is ready below; click a white square to place a bulb.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Place or remove a bulb | Arrow keys to move, Enter to toggle | Left-click |
| Mark a square as having no bulb | Space or I | Right-click |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
| Show the solution | — | Game menu → Solve |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Light Up is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
- A bulb lights its own square and every square in a straight line up, down, left and right until a black square or the edge stops it.
- Every white square must be lit.
- No bulb may be lit by another bulb.
- A numbered black square must have exactly that many bulbs directly above, below, left and right of it. Unnumbered black squares have no limit.
Bulbs that see each other and numbers that are wrong or cannot be met are shown in red.
Sizes and difficulty
Presets come at 7×7, 10×10 and 14×14 in easy, tricky and hard. Easy puzzles can be solved without guessing; hard ones may need some. Custom also sets the rough share of black squares and their symmetry.
Solving tips
Start with 4s (bulbs on all four sides) and with 0s (mark all neighbours as no bulb). A 3 against an edge or wall, or a 2 in a corner, is also fully forced. Then look for white squares that can only be lit from one place: if a square's row and column are all blocked or already marked, the bulb must go on the square itself. Mark no-bulb squares freely; it makes the remaining options obvious.
Where this puzzle comes from
Light Up is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Can a bulb sit next to an unnumbered black square?
Yes. Only numbered black squares restrict how many bulbs are around them.
Do lit squares need to be lit by exactly one bulb?
No. A white square may be lit by several bulbs; the only ban is a bulb being lit by another bulb.
Is Light Up free to play here?
Yes, with no limit on the number of puzzles. Light Up is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
More you can play in your browser
Related guides
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- Mosaic puzzle (Mosaic)Play Mosaic free in your browser: shade squares so every clue matches the number of black
Want a game like this on your own site?
Light Up puzzle (Light Up) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.