Short version: Billie Eilish owns.

Long version, because this guy took notes on his phone for work: There was no doubt that pied piper Eilish ― maybe the most famous teenager in the world, at least to other teenagers ― was going to amass enough people to petition for statehood Saturday at Austin City Limits Music Festival. We all crushed together as the light got low and Juuls lit up. “Who the (expletive) is Ween?” one young guy behind me asked at the highlight reel of ACL Fests past playing on the stage-side screen. Footage of Björk flashed for a minute while visions of Billie danced in our heads, and a lanky kid with a Robert Smith ’do squeezed through the mob. Felt good, felt right, felt like continuity.

The clock struck 7 p.m., and chants of “Billie! Billie!” conjured the lady of the manor, an stone-faced vision in chartreuse. Her video art looked like creepypasta mined from the darkest corner of the internet in 2008. Spiders are always on-trend.

Of course the opening shot was “Bad Guy.”

Eilish bounced around every stretch of stage she could find, a lime sock up here, an orthopedic boot up there. She didn’t need to tell anyone to do the chart-topping single’s handclaps. That song’s generation-defining “duh” was a secret password, too ― she knew that you knew just how to say it.

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Eilish’s brand is Halloween chic, spooky memelord, dancing because the boomers let the world burn and then hid the water buckets. Her talent’s not just branding, though. It’s entertaining. She moves with ease and commands an army with an expression. Her shoulder only shrugs on one side, and she flicks her green press-on nails like she’s studying for her Hogwarts A-levels. (It’s cooler than that sounds. Sorry, I’m 30.) Her voice is pure and haunting, but she’s not afraid to go torchy or droning. When Billie Eilish tells you to open up multiple mosh pits in a crowd packed tighter than canned ham, it just kinda happens. “Wider,” she says. Don’t make her flick a nail again.

“You Should See Me In a Crown” did need those pits; good thinking. Sticky bodies gotta have space to crash into each other. Eilish runs an intimate rock concert.

“You guys, I keep burping up Chipotle,” she laughed. (It was a snort-laugh, for the record.) “It’s crazy.”

Just friends here, ‘kay?

Eilish’s propensity to break composure is Jimmy Fallon-esque, except it’s charming. She performed the big parts (the thrashing; lying on-stage to dream auto-tuned dreams) and the small parts (little moments with her 10 fingers splayed wide; an eye-roll where you gotta have one; air-drumming, always crucial). Does a critical assessment of a performance matter when the singer's a whole moment?

After “All the Good Girls Go to Hell,” someone yelled “What’s next? Feed us!” So, Eilish served up a piping hot “Bellyache,” her brother Finneas backing her up with some Spanish-tinged guitar. (Finneas, her chief collaborator, also performed a solo set earlier in the day.)

You should get “it,” if you don’t already, by the time you finish seeing Eilish. It’s not enough to say that she’s “different,” or that she’s doing music in a way no one else is, or that she’s talking to her generation about things that they have to face (recreational Xanax, crippling existential dread) in a smart, idiosyncratic way.

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But if you need it spelled out, here’s the “Sesame Street” version. When Eilish started singing her breakout smash “Ocean Eyes,” she walked down the path separating the two sides of the audience. “Ocean Eyes” is a beautiful song about infatuation, not quite in keeping with the tracks on her more sinister debut album, "When We All Fall Asleep, Where Do We Go?" (which the song predates).

Eilish started out grazing the outstretched hands like you’re used to seeing a pop idol do at an ACL Fest show. But then there seemed to be more and more hands, and she started to linger a little too long with each step for her security’s comfort, obviously. All the scene needed was Eilish on a donkey and a few palm fronds stuck along the path.

Then Eilish went in for the selfies, and that was a ballgame. She leaned back on the barricade into the waiting arms of several young women. They all laughed, together.

Yeah, Billie Eilish owns.