The concept of sending Christmas cards to your loved (and not-so-loved) ones during the festive season has taken an interesting twist, after the GCHQ sent a series of mysterious messages to the British public.
The spy agency's director Robert Hannigan posted a puzzle in his annual message, giving recipients till 31 January 2016 to send their answers in.
However, Hanningan and team may have underestimated human intelligence as code-breakers have posted their versions of the answers on Reddit.
According to instructions posted on the agency's site, "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."
Responding to the challenge, Reddit user oneweirdglobe, posted:
What you are essentially seeing is a QR code, which can be scanned by a mobile phone, moving the code-cracker to the next stage of the puzzle.
Other questions in this category included:
"I was looking at a man on top of a hill using flag semaphore to send a message, but to me it looked like a very odd message. It began "ZGJJQ EZRXM" before seemingly ending with a hashtag. Which hashtag?" The options? #SGM #SEM #SEN #SGN #TEN
Getting the right answers then unlocks part 3:
If you're still keen to power through the rest of the brain teasers, parts 4 and 5 look like this:
When we asked GCHQ about the number of correct submissions they've had so far, they were equally cryptic and told us results would only be announced in January.
The winner will be drawn from all the successful entries and players are invited to make a donation to the 'National Society for the Prevention of Cruelty to Children.'
Well, at least we all have options if the conversation around the dinner table gets too boring on Christmas Day.