The U.K’s Creepy Surveillance Agency Is Wishing You a Happy Holiday With This Puzzle. Woo.

I don’t know about you, but when I think holiday fun I think nonograms.

Puzzle by GHCQ

The holiday season is fun but can also be stressful. And nothing says “relax and enjoy time with friends and family” like a tricky puzzle from one of the world’s most powerful and invasive intelligence agencies. Right?

The United Kingdom’s Government Communications Headquarters is known for publishing cryptic brainteasers, and agency director Robert Hannigan is sending the one above with his Christmas cards this year. (BBC News reports that the cards have a nativity scene on them.)

GCHQ says that the puzzle has multiple stages—as you make progress you reveal clues about how to continue. Players can send their solutions to the agency between now and the end of January, but it seems like you have to get to a certain point in the puzzle to even figure out what the email address is.

GCHQ explains how the brainteaser works.

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.

The agency clearly knows it has an audience for these puzzles, and it seems to be a vocal group. One Guardian article about the puzzle has hundreds of impassioned comments. “This one is pretty tricky, but not as hard as last week’s GCHQ/MI6 riddle,” wrote HoofHeartedOne. OhReallyFFS added, “It’s a pissing nonogram, I was doing them 25 years ago in my Mother’s copy of the Sunday Telegraph. There’s loads of apps for these now-a-days. Now fuck off GCHQ.” Strong words.

GCHQ’s website has been down on and off for hours, though it’s not clear if the outage is related to the puzzle. You know what they say—too much raging puzzle fun crashes servers.