In an attempt to get some positive coverage for a change, GCHQ has released a Christmas card and, naturally, it comes with a twist. Rather than featuring a black-and-white picture camera lens and the message, “Always thinking about you,” the card comes with a rather clever puzzle, alongside a series of instructions and Adoration of the Shepherds, a painting by one of Rembrandt's old pupils.
You can find the grid-shading puzzle above (click to enlarge). Here are GCHQ's instructions:
In this type of grid-shading puzzle, each square is either black or white. Some of the black squares have already been filled in for you. Each row or column is labelled with a string of numbers. The numbers indicate the length of all consecutive runs of black squares, and are displayed in the order that the runs appear in that line. For example, a label "2 1 6" indicates sets of two, one and six black squares, each of which will have at least one white square separating them.
Hmm. If you got anything from that and somehow manage to crack the code, you'll have also created puzzle two. Solve that and you'll unlock puzzle three (and so on). Once you've completed the series of challenges, you're invited to send your card back to GCHQ via email. If you get it across to them before the start of February 2016, a slip of paper with your name on it will be thrown into a hat. If it's then drawn from that hat, you'll probably win something, like a job. [Register]