Fans of codebreaking, maths and brainteasers can now try their hand at the latest cryptic Christmas challenge set by GCHQ, the UK's intelligence agency.
GCHQ released its annual Christmas card on Wednesday, external, filled with puzzles and hidden codes designed to help children aged 11-18 hone a range of skills "they might need to become a spy".
The card was created by "schoolchildren as well as spies", according to GCHQ, after hundreds of young people entered a design competition in the lead-up to the festive period.
It contains seven puzzles set by "GCHQ's in-house puzzlers", geared towards testing a range of problem-solving skills including intuitive reasoning and lateral thinking.
Students were asked to draw their response to the question: "What do you think GCHQ looks like on Christmas Day?". They were challenged to embed hidden codes and ciphers into their designs.
Three winners were selected by a panel of judges across three age groups.
The famously tricky puzzles "aren't meant to be solved alone", GCHQ said, adding: "We believe the right mix of minds means we can solve seemingly impossible problems."
"Puzzles are at the heart of GCHQ's work to keep the country safe from hostile states, terrorists and criminals; challenging our teams to think creatively and analytically every day," said GCHQ director Anne Keast-Butler.
She said she hoped the puzzle encourages the next generation "to explore STEM (science, technology, engineering and maths) subjects and consider the rewarding careers available in cybersecurity and intelligence".
Meanwhile, the spy agency's "Chief Puzzler", known only as "Colin", said the puzzles are designed to test "the same blend of skills our teams use every day to keep the country safe."
Answers were released on Wednesday evening - so you can see below whether you've got the puzzles correct.