Well damn, I did not see this coming.

The best film in ages about coming to grips with “fluid” gender issues so dominating film, TV and other media these days is smart, reassuringly sweet and Polish.

I dare say you know someone in your life who is dealing with this culture-roiling issue — an uncertain kid, a confused parent wondering if “just a phase/cry for attention” is wishful thinking, an intolerant relative or politician figuring he/she can wish or legislate it away — who’d get something out of “Fanfic,” the story of an angry, pill-popping motherless teen who stops being angry the minute she tries on a boyfriend’s clothes.

Model/actress Alin Szewczyk stars as Toska, the unhappiest kid at her high school. Eating-disorder-thin, she’s got razor marks on her wrists and a tendency to steal her contruction foreman father’s pain pills.

Toska’s only escape is writing “fanfic,” a Polish fan fiction that isn’t exactly like the fan-written further adventures of popular intellectual property characters from “Star Trek” and comic books and the like that blew up in the West. She imagines herself as a rock star or whoever, writes a story about that and posts it online, where others give her affirmation for this introverted creative outlet.

But one day, throwing up in the toilet during a “welcome back to school” assembly, Toska has a “meet cute.” The new boy, Leon (Jan Cieciara) is throwing up in the next stall.

He makes the effort at friendship, maybe even flirting. But we’ve established that tough-girl Toska is above all that. She is asexual and friendless, the class “weirdo” (in Polish with subtitles, or dubbed into English).

Leon persists, and something about him gets her fancy. She starts writing fanfic of herself as a rock star and Leon as a cross-dressing guitarist in her band.

And one party invitation later, she gets soaked on the walk over, he lends her some clothes, and Toska’s makeover becomes her transformation. The stress is gone with the hair and Leon helps her trim.

Her widowed dad (Dobromir Dymecki) may wish she’d “act like a normal girl,” and “stop playing ‘dressup’ already.” But Toska has changed her look, consulted Youtube videos on taping down her breasts and changed her pronoun and name to the more masculine “Tosiek.”

That complicated enough? No? Did I mention Leon’s gay, and crushed-on by a gay classmate? And yet he and Tosiek are still drawn to each other.

Tosiek is too young to know how to process or at least articulate what’s happening.

“I just know when something feels right and when it doesn’t.”

And no matter what school bullies, online trolls or a particularly intolerant teacher — “Did you watch too many American movies?” is her best put-down. — say, that settles it with Tosiek and with Leon.

Adapted from a novel by Natalia Osińska, “Fanfic” loses track of the fan fiction subtext (Tosiek’s imagined black and white movies of rock stardom with Leon in drag) after that dominates the early acts.

But what director and co-writer Marta Karwowska gets out of this is a lived-in school life, kids who flirt and fight and flee and bully like real teens, a realistic depiction of confusion-based anger and “dysphoria” and a hopeful note that if Poland, ground zero and eager participant in the Holocaust, may just catch on, with or without “too many American movies.”

Tosiek speaks for cultures and generations in a single, simple line explaining a botched co-written class assignment about a topic that is eating up a lot of headspace in cultures around the world.

“Gender is BORING.” And if today’s teens and 20somethings do their part in erasing it as “an issue,” that might be a public service no one saw coming.

Rating: TV-MA, violence, teen drinking, sexuality

Cast: Alin Szewczyk, Jan Cieciara, Maja Szopa, Krzysztof Oleksyn, Ignacy Liss, Agnieszka Rajda and Dobromir Dymecki

Credits: Directed by Marta Karwowska, scripted by Marta Karwowska and Grzegorz Jaroszuk, based on a novel by Natalia Osińska. A Netflix release.

Running time: 1:36