This was the crossword puzzle in the New York Times yesterday. 

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.

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.