Sorry, this Javascript puzzle doesn't seem to work in your web
browser. Perhaps you have Javascript disabled, or perhaps your browser
doesn't provide a feature that the puzzle code requires (such as
typed arrays).
These puzzles have been successfully run in Firefox 19, Chrome 26,
Internet Explorer 10 and Safari 6.
Left-click to colour a square black. Right-click to mark a square
with a dot, if you know it should not be black.