Can You Solve The GCHQ Christmas Card Puzzle?
British eavesdropping agency GCHQ is sending out a Christmas card this year, which includes a festive brainteaser that will keep puzzle fans busy over the season of goodwill.
The greeting from the director of the Cheltenham-based top-secret listening post contains a cryptographic challenge to exercise the grey cells of armchair agents. Players have to fill in a grid-shading puzzle, which will create a picture that leads to a series of increasingly complex challenges. Those taking part are invited to make a donation to the NSPCC children's charity.
GCHQ said: "This year, along with his traditional Christmas cards, Director GCHQ Robert Hannigan is including a brain-teasing puzzle that seems certain to exercise the grey matter of participants over the holiday season.
"The card, which features the 'Adoration of the Shepherds' by a pupil of Rembrandt, includes traditional Christmas greetings from Director on behalf of the department. "However, unlike previous years, the 2015 card will contain a grid-shading puzzle and instructions on how it should be completed."
Once all stages have been unlocked and completed successfully, players are invited to submit their answer via a given GCHQ email address by 31 January. The winner will then be drawn from all the successful entries.
Those not on the spy chief's Christmas card list can download the puzzle here.
Explaining how to get started, the GCHQ website states: "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."
Dr Gareth Moore, puzzle author and creator of the website Brained Up, designed a series of brainteasers similar to the GCHQ one, including one which produced 'Sky' when solved. He said the GCHQ puzzle is "only difficult in appearance" and is just "a question of being patient…In actual fact, a picture puzzle like this can actually be solved by considering each row and each column one by one," he said.
"So the puzzle already has some squares shaded in - in fact, those are Morse code that spell out 'GCHQ', which is not actually relevant at all to the puzzle, it's just something they've done to make it a bit fun, I think…The secret to doing a puzzle like this is to do it row by row and to put a little x or a dot when you work out where a gap is - the difficult thing perhaps is working out where to start."
Sky:
