Crossword puzzles are fleeting things. Sure, some get anthologized in books, but most are solved or abandoned in frustration, then piled up with the rest of the morning’s paper, tossed into the recycling bin, and forgotten.

Thursday’s New York Times puzzle will be different.

(Note: There are major crossword spoilers below. If you’d like, go and solve the puzzle before reading the story behind its creation. We’ll be here when you get back.)

Ben Tausig, the Stony Brook University professor of ethnomusicology and crossword constructor who wrote the puzzle, tweeted the following three weeks ago:

I'm pretty sure that, in an important respect, it's the first of its kind. — datageneral (@datageneral) August 9, 2016

Why was Tausig so excited? For starters, he pulled off a great technical feat. Tausig’s crossword is a so-called Schrödinger puzzle, named for the physicist’s hypothetical cat that is at once both alive and dead. In a Schrödinger puzzle, select squares have more than one correct letter answer: They exist in two states at once. “Black Halloween animal,” for example, could be both BAT or CAT, yielding two different but perfectly correct puzzles. Only 10 such puzzles have now been published in Times history.

It’s the theme of Tausig’s puzzle, though, that makes it special. Four entries in Thursday’s crossword can include either an “F” or an “M.” Both are correct; neither is wrong. For example, “Part of a house” can be either ROOF or ROOM. The long “revealer” answer, tying those select entries together and spanning 11 squares smack-dab in the middle of the puzzle, is GENDER FLUID.

In a literal sense, this is a first for the Times. The phrase “gender fluid” has never been in an NYT crossword before, nor has the word “queer,” which also appears in the puzzle, been clued in its LGBTQ sense. It’s always been “odd” or “mysterious.”

The most famous Schrödinger puzzle, and maybe the most famous crossword puzzle in American history, was published on the morning of Election Day in 1996. The clue for the two central entries read “Lead story in tomorrow’s newspaper (!).” A bold clue indeed! The correct answer could read either CLINTON ELECTED or BOB DOLE ELECTED. Will Shortz, the Times’ longtime puzzle editor, has called it his favorite crossword.

Thursday’s GENDER FLUID puzzle may be just as noteworthy. “I think that people are going to enjoy this puzzle because it’s sort of a monument to how far queerness has come,” Tausig told me in an interview. “And ideas about gender identity that weren’t mainstream 20 years ago or even five years ago.”

One early review indicates Tausig was right. “I think it’s wonderful,” Deb Amlen, the columnist and editor of Wordplay, the Times’ crossword column, told me. “As a parent of a young adult child who is gender fluid, Ben’s puzzle affected me deeply. It’s exciting to see the development of more progressive and accepting language around the topic of gender.”

The phrase “gender fluid” dates to at least 1994, and its usage online quickly accelerated around 2014. It means “of, relating to, or being a person whose gender identity is not fixed,” per Merriam-Webster. This puzzle, with “M”s and “F”s that aren’t fixed, is a masterful blend of subject and structure. “It potentially really evokes what gender fluidity is, which is not moving back and forth between two poles, but actually not being committed to either pole, and potentially existing in many states at different times,” Tausig said.

Thursday’s puzzle has been many months in the making. Shortz shared with me the email correspondence between him, another Times puzzle staffer, and Tausig. It stretches from January to mid-August. Early on, Tausig expressed concern that the term “gender fluid” might be perceived as controversial, and there was worry from the Times that many solvers wouldn’t be aware of the concept. (Shortz himself wasn’t aware of it in January.) But they pressed on, discussing intricacies of cluing and potential puzzle fill, and deciding it’d be better as a Thursday puzzle than a Sunday. (Thursday grids are smaller than Sundays, and they were struggling to find longer, workable Schrödinger entries.) “This is a yes,” Shortz eventually wrote in early August.

But in this world, in 2016, where homophobia remains rampant and political correctness is feverishly litigated online and off, some residual concern remains. “I don’t think you get a lot of canceled subscriptions over your average, even bad, crossword,” Tausig, himself a puzzle editor, said. “I’m sure this will get canceled subscriptions.”

What makes Tausig’s puzzle particularly fascinating is that the Times—the world’s leading puzzle institution—has been criticized, including in Slate, for its cluelessness and tone deafness on issues of gender, not to mention race. Recent solecisms have included the clue “Exasperated comment from a feminist” for the answer MEN, and “Decidedly nonfeminist women’s group” for HAREM. The latter was described by solvers as “hateful” and “awful.” The clue “Gangsta rap characters” led to the answer THUGS.

Michael Sharp, the Times puzzle’s most vocal critic, blogs under the name Rex Parker. “I don’t think the Times is particularly hostile to any group,” he told me. “I just think that it doesn’t care about the living nature of language in America today. Except maybe belatedly. If it’s forced to, it will.” In this case, it has embraced that living nature.

Are crosswords political speech? Yes, sometimes—if not on the bleeding edge. They’re a barometer of our language, Tausig has said, while Sharp describes them as a statement about what counts as common knowledge. Crosswords may be a lagging indicator of the state of our world, but when they say something, it means something. “A puzzle isn’t necessarily a political statement,” Sharp said, “but it can be. A clue isn’t, but it can be.” In 1997, GAY was clued as “___ Men’s Health Crisis.” In 2007, it was “Party to many a civil union.” And last year, at last, it was “___ marriage.”

Sharp liked this puzzle. As a crossword critic, he saw cruciverbal value more so than political value. “Awareness of a broader world beyond a straight, white, male world just makes for more opportunities for good, playful cluing,” he said. There are benefits to openness “not just from a political angle but from a puzzle angle.”

I asked Shortz if publishing the “gender fluid” puzzle was a response to any criticism.

“No, this puzzle is not a response to anything,” he said. “It’s just a good puzzle.”