Can you solve this Christmas card puzzle created by British spies?
How does a spy wish you a Merry Christmas? With a card containing a mind-boggling logic puzzle.
The complex brainteaser was sent out by the British surveillance agency GCHQ with its holiday cards. It requires a logical mind to figure it out. But New York Times crossword puzzle editor Will Shortz says that this kind of challenge can be addictive.
"I love this kind of puzzle," Shortz tells As It Happens host Carol Off. "I first saw it in 1992 when some Japanese puzzlers came to New York. I was absolutely entranced. It was the only time I ever missed my subway stop, I was so engrossed."
To solve the puzzle, you have to blacken squares in each row and column corresponding to the numbers on the side and leave white squares in between. The trick is to figure out where to put the white ones. The finished puzzle creates an image.
In the GCHQ puzzle, a few squares are already black. Shortz points out that they are Morse code for GCHQ.
If you can solve the puzzle, the answer will lead you to a series of other, increasingly difficult, challenges.
Given that the spy agency is currently hiring, Carol Off wonders, might the puzzle challenge be part of some sort of recruitment drive?
"So you saw The Imitation Game and that was based on history. There was a crossword tournament in London sponsored by The Daily Express, in 1939, I think, and that was a tool for breaking codes for the British government in World War II," Shortz says.
"I think that someone who could solve this and then move on to solve the more difficult challenges would be somebody they'd be interested in hiring."
To hear Shortz's tip for getting started on the puzzle, select "Listen" above.