NOTE: A version of the puzzle with answers appears below.

It's being called one of the most important crosswords in the history of The New York Times.

Thursday's puzzle stands out because of the word at its centre — the "revealer" — and for the clever way the solution comes together.

I thought it was high time. - Ben Tausig, crossword creator

Don't read any further, if you are planning to do the puzzle later.

Seriously.

We mean it...

Stop.

The reveal in the middle squares is "gender fluid." And it's the first time the term has ever been used in a Times puzzle. The puzzle's creator, Ben Tausig, said he wanted to use a queer theme to push the newspaper's boundaries.

"I know that The Times hasn't done a puzzle quite like this in the past and I thought it was high time that they did," Tausig tells As It Happens guest host Laura Lynch.

NYT Crossword clues can seem...fusty (or is it musty?) to many, but <a href="https://twitter.com/datageneral">@datageneral</a>'s puzzle today is progressive and brilliant and super fun. —@ericdharvey

Tausig first approached Times crossword editor Will Shortz with his puzzle theme in January. Shortz had never heard the phrase "gender fluid," which the Oxford Dictionary defines as "denoting or relating to a person who does not identify themselves as having a fixed gender."

It then took Tausig months of work to create the finished crossword. Part of the challenge was his decision to make it a Schrödinger puzzle, named after the scientist's thought experiment where a cat in a box is both dead and alive at once. In the crossword, there are some clues with two correct answers, words with one interchangeable letter.

The word "gender fluid" has never been used in a New York Times crossword before. (New York Times)

For example, "part of a house" can be answered with either "roof" or "room." And a "word that can precede 'sex'" can be solved with both "same" or "safe." In each case, the letters swapped are M and F — which, of course, stand for "male" and "female."

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"What that represents is the fact that, on the one hand, the squares can be either male or female, but on the other hand, they are definitively neither," Tausig says. "That to me kind of elegantly represented the concept of gender fluidity."

You can play the crossword here (subscription required).

For more on how the crossword came together, listen to our full interview with Ben Tausig.