Light Up

from Simon Tatham's Portable Puzzle Collection


If you've been reading this message for more than a second or two, then this WebAssembly puzzle doesn't seem to be working in your web browser. Sorry!

More information

Most modern browsers should support WASM. I've had reports of success from:

If this puzzle isn't working in one of those browsers (or a later version), check to see whether you have any local configuration that might have turned off WebAssembly completely, or some kind of blocking software that might have prevented the WASM code from being downloaded in the first place.

(For example, in Firefox, it's possible to turn off WASM completely by setting javascript.options.wasm to false in the about:config interface. If you've done that, or something analogous in another browser, this puzzle won't run.)

In other browsers, the problem might be that WebAssembly isn't supported at all (for example, Internet Explorer 11), or that a browser update is needed.

If you think that your browser should support WebAssembly, but this puzzle still isn't running, then please report the problem, including as much diagnostic information as you can find.

In particular, try opening your browser's Javascript error console and then reloading this page, and tell me if it reports any error messages.

Also, if your browser has a network diagnostic tab, try the same experiment, to make sure it is successfully loading both of the auxiliary files lightup.js and lightup.wasm.


Place light bulbs in the grid so as to light up all the blank squares. A light illuminates its own square and all the squares in the same row or column unless blocked by walls (black squares). Lights may not illuminate each other. Each numbered square must be orthogonally adjacent to exactly the given number of lights.

Click on a square to place or remove a light. Right-click to place a dot indicating that you think there is no light in that square.

Full instructions | Back to main puzzles page


(comments to anakin@pobox.com)
(thanks to chiark for hosting this page)
(last modified on Wed May 26 01:48:18 2021)